Patent Publication Number: US-2023154502-A1

Title: Low Power Memory System Using Dual Input-Output Voltage Supplies

Description:
RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 17/158,485 filed on Jan. 26, 2021, entitled “Low Power Memory System Using Dual Input-Output Voltage Supplies,” the entire contents of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Next generation low-power double data rate (LPDDR) memory (e.g., LPDDR6) can offer a balance of high performance, low power, competitive memory cost, various package types, and multi-sourcing availability that are attractive for mobile and non-mobile applications. 
     SUMMARY 
     Various disclosed aspects may include apparatuses and methods for memory system using dual input/output (IO) voltage supplies. Various aspects may include a computing device memory system having a memory device, a memory physical layer communicatively connected to the memory device, a first input/output (IO) voltage supply electrically connected to the memory device and to the memory physical layer, and a second IO voltage supply electrically connected to the memory device and to the memory physical layer, in which the memory device and the physical layer may communicate data of a memory transaction using a 3 level pulse amplitude modulation (PAM) IO scheme. 
     In some aspects, the first IO voltage supply is a first dedicated IO voltage supply, and the second IO voltage supply is a second dedicated IO voltage supply. 
     In some aspects, the first IO voltage supply is a dedicated IO voltage supply, and the second IO voltage supply is a shared IO voltage supply. 
     Some aspects may further include a first core voltage supply and a second core voltage supply, in which each of the first core voltage supply and the second core voltage supply are electrically connected to the memory device, and in which the shared IO voltage supply is electrically connected to the second core voltage supply. 
     Some aspects may further include a third core voltage supply, in which the third core voltage supply is electrically connected to the memory device, and in which a voltage of the second core voltage supply is greater than a voltage of the third core voltage supply. 
     Some aspects may further include a first core voltage supply, a second core voltage supply, and a third core voltage supply, in which each of the first core voltage supply, the second core voltage supply, and the third core voltage supply are electrically connected to the memory device, in which the shared IO voltage supply is electrically connected to the third core voltage supply, and in which a voltage of the second core voltage supply is greater than a voltage of the third core voltage supply. 
     In some aspects, a voltage of the second IO voltage supply is greater than a voltage of the first IO voltage supply. 
     In some aspects, the data of the memory transaction is binary data, and the memory device and the memory physical layer may further convert between the binary data and 3 level PAM IO scheme signals using the first IO voltage supply and the second IO voltage supply. 
     In some aspects, the memory device may encode the data of the memory transaction for generating a 3 level PAM signal, and generate the 3 level PAM signal by controlling selective electrical connection of the first IO voltage supply, the second IO voltage supply, or a ground to a component of the memory device according to the encoded data. 
     In some aspects, the memory physical layer may encode the data of the memory transaction for generating a 3 level PAM signal, and generate the 3 level PAM signal by controlling a selective electrical connection of the first IO voltage supply, the second IO voltage supply, or a ground to a component of the memory physical layer according to the encoded data. 
     Various aspects include computing devices having means for performing any of the functions of the computing device summarized above. Various aspects include methods to perform any of the functions of the computing device summarized above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate example embodiments of various embodiments, and together with the general description given above and the detailed description given below, serve to explain the features of the claims. 
         FIG.  1    is a component block diagram illustrating an example computing device suitable for implementing various embodiments. 
         FIGS.  2 A- 2 C  are component block diagrams illustrating example memory system using dual input/output (IO) voltage supplies for implementing various embodiments. 
         FIG.  3    is a component block diagram illustrating an example dual IO voltage 3 level pulse amplitude modulation (PAM or PAM-3) IO structure for implementing various embodiments. 
         FIG.  4    is a signal timing diagram illustrating an example dual IO voltage 3 level PAM voltage level signals for implementing various embodiments. 
         FIG.  5    is a table illustrating an example of 3 level PAM coding for implementing various embodiments. 
         FIGS.  6 A and  6 B  are component block diagrams illustrating example dual IO voltage memory system interfaces for 3 level PAM IO schemes for implementing various embodiments. 
         FIG.  7    is a set of tables illustrating an example of signal allocation in a dual IO voltage memory system interface for 3 level PAM IO schemes for implementing various embodiments. 
         FIG.  8    is a process flow diagram illustrating a method for dual IO voltage 3 level PAM IO according to some embodiments. 
         FIG.  9    is a component block diagram illustrating an example mobile computing device suitable for implementing various embodiments. 
         FIG.  10    is a component block diagram illustrating an example mobile computing device suitable for implementing various embodiments. 
         FIG.  11    is a component block diagram illustrating an example server suitable for implementing various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes, and are not intended to limit the scope of the claims. 
     Various embodiments include circuitry, methods, and computing devices implementing such methods for memory systems using dual input/output (IO) voltage supplies. Some embodiments may include memory systems having dual input/output (IO) voltage supplies in which a memory interface of a system on chip (SoC) and an IO block of a memory device are connected to and receive voltage from dual IO voltage supplies. Some embodiments may include IO structures configured to implement 3 level pulse amplitude modulation (PAM or PAM-3) using dual IO voltages. 
     The terms “computing device” and “mobile device” are used interchangeably herein to refer to any one or all of cellular telephones, smartphones, personal or mobile multi-media players, personal data assistants (PDA&#39;s), laptop computers, tablet computers, convertible laptops/tablets (2-in-1 computers), smartbooks, ultrabooks, netbooks, palm-top computers, wireless electronic mail receivers, multimedia Internet enabled cellular telephones, mobile gaming consoles, wireless gaming controllers, and similar personal electronic devices that include a memory, and a programmable processor. The term “computing device” may further refer to stationary computing devices including personal computers, desktop computers, all-in-one computers, workstations, super computers, mainframe computers, embedded computers, servers, home theater computers, and game consoles. 
     The adjectives “high,” “higher,” “low” and “lower” are used herein as relative terms to distinguish different levels of voltage or power demand characterizing various aspects, such as voltage supplies, IO schemes, memory systems, etc. For example, two voltage supplies included in a memory system that differ in terms of their voltage levels may be distinguished in the following descriptions of various embodiments as a “high voltage supply” and a “low voltage supply.” The terms “high,” “higher,” “low” and “lower” are not intended to indicate or suggest a particular value of level of the characterized aspect. For example, the voltage of a “high voltage supply” may differ from the voltage of a “low voltage supply” by one, two or a few volts. 
     Embodiments described herein include memory systems using dual IO voltage supplies for implementing a 3 level PAM IO scheme, that enable improved performance and reduced power demand compared to conventional memory systems. The memory systems may include a memory interface of an SoC and an IO block of a memory device connected to and configured to receive voltage from dual IO voltage supplies. In some embodiments, the dual IO voltage supplies may include two dedicated TO voltage supplies. In some embodiments, the dual TO voltage supplies may include a dedicated TO voltage supply and a shared TO voltage supply. The shared TO voltage supply may include a core voltage supply of the memory device. In some embodiments, shared TO voltage supply may include a core high voltage supply of the memory device. In some embodiments, the shared TO voltage supply may include a core low voltage supply of the memory device. As used herein, the term “TO voltage supply” refers to a voltage supply connected to the TO block of the memory device. As used herein, the term “core voltage supply” refers to a voltage supply connected to the internal circuitry of the memory device, which may include, for example, a memory bitcell array. As used herein, the term “shared TO voltage supply” refers to a voltage supply connected to the TO block and to a core voltage supply. 
     In some embodiments, an TO block of the memory device may include structures configured to control an output of signals for implementing the 3 level PAM IO scheme. The TO block may be, for example, a 3 level pulse amplitude modulator. The TO block may receive a data signal and encode the data signal to transmitter input signals. The TO block may interpret the transmitter input signals and control selection and output of the voltage supplied to the TO block from the dual TO voltage supplies configured to represent the signal states of the 3 level PAM IO scheme. In some embodiments, the TO block may also receive 3 level PAM signals, and include structures configured to convert the 3 level PAM signals to data signals and output the data signals. In some embodiments, the TO block may compare the 3 level PAM signals to voltage reference signals, which may generate and output receiver output signals. The TO block may decode the receiver output signals and generate and output the data signals. 
     In some embodiments, system error correction code (ECC), link ECC, or other system functions may be supported to enhance memory system reliability and stability. The ECC or other system function values may be encoded and decoded along with the data signals as part of the 3 level PAM IO scheme. 
     Using the dual IO voltage supplies to implement the 3 level PAM IO scheme allows for increased bandwidth for communication with the memory device by increasing the number of IO signaling levels used in such communication as compared to two IO signaling level (e.g., high and low) schemes. While providing higher memory system bandwidth than existing low-power double data rate memory (LPDDR) specifications (e.g., LPDDR5), the IO signaling levels increase and dual rank support allow for flexible memory package options and configurations that many systems require without significant cost overhead. 
     Further, embodiments described herein provide memory systems using an IO scheme that draws less power than conventional single IO voltage 3 level PAM scheme memory systems. By using a lower voltage IO voltage supply in addition to an existing higher IO voltage supply, overall memory system power consumption may be reduced as the higher IO voltage supply may be used less often, such as when the lower voltage IO voltage supply is used. Additionally, in some embodiments, by sharing a memory core voltage supply with one of the dual IO voltage supplies, there may be no further system cost overhead to support the additional IO voltage supply in the memory system. 
     Some of the embodiments described herein may be particularly well suited for memory sub-systems and memory devices for user equipment, mobile computing, automotive, and artificial intelligence systems by providing high performance, memory systems. In particular, various embodiments may be implemented with next generation LPDDR specification (LPDDR6) and associated double data rate memory (DDR) physical layer (PHY) chipsets used in mobile device or non-mobile computing devices. 
       FIG.  1    illustrates a system including a computing device  10  suitable for use with various embodiments. The computing device  10  may include a system-on-chip (SoC)  12  with a processor  14 , a memory  16 , a memory physical layer  34 , a communication interface  18 , a storage memory interface  20 , a clock controller  30 , and an interconnect  32 . The computing device  10  may further include a communication component  22 , such as a wired or wireless modem, a storage memory  24 , an antenna  26  for establishing a wireless communication link, a power manager  28 , and a memory  36 . The processor  14  may include any of a variety of processing devices, for example a number of processor cores. 
     The term “system-on-chip” (SoC) is used herein to refer to a set of interconnected electronic circuits typically, but not exclusively, including a processing device, a memory, and a communication interface. A processing device may include a variety of different types of processors  14  and processor cores, such as a general purpose processor, a central processing unit (CPU), a digital signal processor (DSP), a graphics processing unit (GPU), an accelerated processing unit (APU), a secure processing unit (SPU), neural network processing unit (NPU), a subsystem processor of specific components of the computing device, such as an image processor for a camera subsystem or a display processor for a display, an auxiliary processor, a single-core processor, a multicore processor, a controller, and a microcontroller. A processing device may further embody other hardware and hardware combinations, such as a field programmable gate array (FPGA), an application-specific integrated circuit (ASIC), other programmable logic device, discrete gate logic, transistor logic, performance monitoring hardware, watchdog hardware, and time references. Integrated circuits may be configured such that the components of the integrated circuit reside on a single piece of semiconductor material, such as silicon. 
     An SoC  12  may include one or more processors  14 . The computing device  10  may include more than one SoC  12 , thereby increasing the number of processors  14  and processor cores. The computing device  10  may also include processors  14  that are not associated with an SoC  12 . The processors  14  may each be configured for specific purposes that may be the same as or different from other processors  14  of the computing device  10 . One or more of the processors  14  and processor cores of the same or different configurations may be grouped together. A group of processors  14  or processor cores may be referred to as a multi-processor cluster. 
     The computing device  10  may include any number and combination of memories, such as the memory  16  integral to the SoC  12  and the memory  36  separate from the SoC  12 . Any of the memories  16 ,  36  may be a volatile or non-volatile memory configured for storing data and processor-executable code for access by the processor  14 . The computing device  10  and/or SoC  12  may include one or more memories  16 ,  36  configured for various purposes. One or more memories  16 ,  36  may include volatile memories such as random access memory (RAM) or main memory, including static RAM (SRAM), such as the memory  16 , dynamic RAM (DRAM), such as the memory  36 , or cache memory. These memories  16 ,  34  may be configured to temporarily hold a limited amount of data received from a data sensor or subsystem, data and/or processor-executable code instructions that are requested from a non-volatile memory  16 ,  24 ,  36  loaded to the memories  16 ,  34  from the non-volatile memory  16 ,  24 ,  36  in anticipation of future access based on a variety of factors, and/or intermediary processing data and/or processor-executable code instructions produced by the processor  14  and temporarily stored for future quick access without being stored in non-volatile memory  16 ,  24 ,  36 . The memory  16 ,  36  may be configured to store data and processor-executable code in parts of the memory  16 ,  36  configured to store data and processor-executable code for secure computing operations, referred to herein as a secure portion. The memory  16 ,  36  may be configured to store data and processor-executable code in parts of the memory  16 ,  36  configured to store data and processor-executable code for non-secure computing operations, referred to herein as a non-secure portion. 
     The memory physical layer  34  may work in unison with the memory  36  to enable the computing device  10  to store and retrieve data and processor-executable code on and from the memory  36 . The memory physical layer  34  may control access to the storage memory  36  and allow the processor  14  to read data from and write data to the memory  36 . 
     The storage memory interface  20  and the storage memory  24  may work in unison to allow the computing device  10  to store data and processor-executable code on a non-volatile storage medium. The storage memory  24  may be configured much like an embodiment of the memory  16  in which the storage memory  24  may store the data or processor-executable code for access by one or more of the processors  14 . The storage memory  24 , being non-volatile, may retain the information after the power of the computing device  10  has been shut off. When the power is turned back on and the computing device  10  reboots, the information stored on the storage memory  24  may be available to the computing device  10 . The storage memory interface  20  may control access to the storage memory  24  and allow the processor  14  to read data from and write data to the storage memory  24 . 
     The power manager  28  may be configured to control power states of and/or power delivery to the components of the SoC  12 . In some embodiments, the power manager  28  may be configured to signal power states to the components of the SoC  12  to prompt the components of the SoC  12  to transition to the signaled power states. In some embodiments, the power manager  28  may be configured to control amounts of power provided to the components of the SoC  12 . For example, the power manager  28  may be configured to control connections between components of the SoC  12  and power rails (not shown). As another example, the power manager  28  may be configured to control amounts of power on power rails connected to the components of the SoC  12 . 
     A clock controller  30  may be configured to control clock signals transmitted to the components of the SoC  12 . In some embodiments, the clock controller  30  may be configured to signal clock states, such as gated or ungated, to components of the SoC  12  to prompt the components of the SoC  12  to transition to the clock state. For example, a component of the SoC  12  may transition to a gated clock state in response to receiving a gated clock state signal from the clock controller  30  by disconnecting from a clock signal and may transition to an ungated clock state in response to receiving an ungated clock state signal from the clock controller  30  by connecting to the clock signal. In some embodiments, the clock controller  30  may be configured to control clock signals to components of the SoC  12 . For example, the clock controller  30  may disconnect a component of the SoC  12  from a clock signal to transition the component of the SoC  12  to a gated clock state and may connect the component of the SoC  12  to the clock signal to transition the component of the SoC  12  to an ungated clock state. 
     The interconnect  32  may be a communication fabric, such as a communication bus, configured to communicatively connect the components of the SoC  12 . The interconnect  32  may transmit signals between the components of the SoC  12 . In some embodiments, the interconnect  32  may be configured to control signals between the components of the SoC  12  by controlling timing and/or transmission paths of the signals. 
     Some or all of the components of the computing device  10  and/or the SoC  12  may be arranged differently and/or combined while still serving the functions of the various embodiments. The computing device  10  may not be limited to one of each of the components, and multiple instances of each component may be included in various configurations of the computing device  10 . 
       FIGS.  2 A- 2 C  illustrates examples of memory systems using dual input/output (IO) voltage supplies for implementing various embodiments. With reference to  FIGS.  1 - 2 C , a memory system  200   a ,  200   b ,  200   c  may be, in whole or in part, integral to an SoC (e.g., SoC  12  in  FIG.  1   ). The memory system  200   a ,  200   b ,  200   c  may include a memory controller  204 , a memory physical layer  206 , any number and combination of memory devices  208  (e.g., memory  16 ,  24  in  FIG.  1   ), and a power management integrated circuit (PMIC)  210  (e.g., power manager  28  in  FIG.  1   ). The memory devices  208  may further include an IO block  212  and any number and combination of memory banks  214 . The IO block  212  may be, for example, a 3 level pulse amplitude modulator. 
     The PMIC  210  may be configured to control and/or provide voltage to the memory device  208  and to the memory physical layer  206 . The PMIC  210  may control and/or provide voltage to the memory device  208  via core voltage supplies  216   a ,  216   b ,  216   c , which may also be referred to as rails, lines, etc. In some embodiments the core voltage supplies  216   a ,  216   b ,  216   c  may include a first core voltage supply  216   a , and a second core voltage supply  216   b  and/or a third core voltage supply  216   c . The core voltage supplies  216   a ,  216   b ,  216   c  may be electrically connected to internal circuitry of the memory device  208 , such as the memory banks  214  or memory bitcell arrays (not shown) of the memory banks  214 . The core voltage supplies  216   a ,  216   b ,  216   c  may be differently configured from each other to provide voltages, alone or in any combination, needed for the memory device  208  to perform any number and combination of functions, including storing, reading, writing, and/or retaining data. In some embodiments, the core voltage supplies  216   a ,  216   b ,  216   c  may be differently configured from each other to provide voltages, alone or in any combination, needed for the memory device  208  to perform any number and combination of the various functions at different speeds and/or for differently sized portions of the memory device  208 . In an example including two core voltage supplies  216   a ,  216   b , the first core voltage supply  216   a  may be greater than the second core voltage supply  216   b . In an example including three core voltage supplies  216   a ,  216   b ,  216   c , the first core voltage supply  216   a  may be greater than the second core voltage supply  216   b , and the second core voltage supply  216   b  may be greater than the third core voltage supply  216   c . As a specific and nonlimiting example, such as per the Joint Electron Device Engineering Council (JEDEC) LPDDR5 specification, the first core voltage supply  216   a  may be approximately 1.8V and the second core voltage supply  216   b  may be approximately 1.05V. As another specific and nonlimiting example, such as per the JEDEC LPDDR5 specification, the first core voltage supply  216   a  may be may be approximately 1.8V, the second core voltage supply  216   b  may be approximately 1.05V, and the third core voltage supply  216   c  may be approximately 0.9V. 
     The PMIC  210  may control and/or provide voltage to the memory device  208  and to the memory physical layer  206  via 10 voltage supplies  218   a ,  218   b , which may also be referred to as rails, lines, etc. The IO voltage supplies  218   a ,  218   b  may be referred to herein together as dual IO voltage supplies. The dual IO voltage supplies  218   a ,  218   b  may include a high IO voltage supply and a low IO voltage supply in which the high IO voltage supply provides a higher voltage than the low IO voltage supply. The voltage provided to the memory device  208  and to the memory physical layer  206  via the dual IO voltage supplies  218   a ,  218   b  may enable the memory system  200   a ,  200   b ,  200   c  to implement a 3 level PAM IO scheme. In some embodiments, the voltage provided to the memory device  208  via the dual IO voltage supplies  218   a ,  218   b  may be provided to the IO block  212  of the memory device  208  to enable the memory device to implement the 3 level PAM IO scheme as described herein. 
     The memory device  208  and to the memory physical layer  206  may be communicatively connected via a communication bus  220 . The communication bus  220  may be configured to transmit signals and data for implementing memory transactions between the memory device  208  and to the memory physical layer  206 . For example, the communication bus  220  may include any number and combination of buses or lines for transmitting data, clock signals, command and address information, etc. In some embodiments, the communication bus  220  may be communicatively connected between the SoC and the memory device  208  external to the SoC. In some embodiments, implementing a 3 level PAM IO scheme using the dual IO voltage supplies  218   a ,  218   b  may decrease power for executing the same memory transactions as compared to IO schemes, such as a 3 level PAM IO scheme, using a single IO voltage supply. The low IO voltage supply of the dual IO voltage supplies  218   a ,  218   b  may provide a lower voltage than the single IO voltage supply, and use of the low IO voltage supply for executing the same memory transactions as the single IO voltage supply may enable the memory device  208  to use less power than executing the transactions using the voltage of the single IO voltage supply. In some embodiments, implementing a 3 level PAM IO scheme using the dual IO voltage supplies  218   a ,  218   b  may increase memory system bandwidth for executing the same memory transactions as compared to IO schemes using a single IO voltage supply. The 3 level PAM IO scheme may be implemented using a greater number of signal states, collectively referred to herein as states, based on the dual IO voltage supplies  218   a ,  218   b  than other IO schemes that use a single IO voltage supply. The greater number of signal states enables encoding a greater amount of data and information in 3 level PAM signals on the communication bus  220  than other IO schemes that use a single IO voltage supply. 
     In some embodiments, the memory system  200   a ,  200   b ,  200   c  may receive memory transactions from any number and combination of processors  202   a ,  202   b ,  202   c  (e.g., processor  14  in  FIG.  1   ). The memory system  200   a ,  200   b ,  200   c  may execute a memory transaction received from a processor  202   a ,  202   b ,  202   c  and/or provide a response of the executed memory transaction to the processor  202   a ,  202   b ,  202   c.    
     In the example illustrated in  FIG.  2 A , the memory system  200   a  may include dedicated IO voltage supplies  218   a ,  218   b  providing the two voltage levels. The PMIC  210  may control and/or provide designated voltages of each of the dedicated dual IO voltage supplies  218   a ,  218   b  to the memory device  208  and to the memory physical layer  206  via individual ones of the dual IO voltage supplies  218   a ,  218   b.    
     In the example illustrated in  FIG.  2 B , the memory system  200   c  may include a shared IO voltage supply  218   a  and a dedicated IO voltage supply  218   b , with the combination providing the two voltage levels. The shared IO voltage supply  218   a  may share a common voltage with the second core voltage supply  216   b  by electrical connection to the second core voltage supply  216   b . The PMIC  210  may control and/or provide a designated voltage of the shared dual IO voltage supply  218   a  to the memory device  208  and to the memory physical layer  206  via controlling and/or providing the designated voltage on the second core voltage supply  216   b . The PMIC  210  may control and/or provide a designated voltage the dedicated IO voltage supply  218   b  to the memory device  208  and to the memory physical layer  206  via the individual dedicated IO voltage supply  218   b.    
     In the example illustrated in  FIG.  2 C , the memory system  200   c  may include a shared IO voltage supply  218   a  and a dedicated IO voltage supply  218   b , with the combination providing the two voltage levels. The shared IO voltage supply  218   a  may share a common voltage with the third core voltage supply  216   c  by electrical connection to the third core voltage supply  216   c . The PMIC  210  may control and/or provide a designated voltage of the shared dual IO voltage supply  218   a  to the memory device  208  and to the memory physical layer  206  via controlling and/or providing the designated voltage on the third core voltage supply  216   c . The PMIC  210  may control and/or provide a designated voltage the dedicated IO voltage supply  218   b  to the memory device  208  and to the memory physical layer  206  via the individual dedicated IO voltage supply  218   b.    
       FIG.  3    is a circuit block diagram illustrating an example dual IO voltage 3 level PAM IO structure for implementing various embodiments. With reference to  FIGS.  1 - 3   , a dual IO voltage 3 level PAM IO structure  300  (e.g., memory physical layer  206 , IO block  212  in  FIGS.  2 A- 2 C ) may include an encoder  302 , a decoder  304 , and any number and combination of 3 level PAM transmitters  306   a ,  306   b , and 3 level PAM receivers  308   a ,  308   b . In some embodiments, the dual IO voltage 3 level PAM IO structure  300  may include two 3 level PAM transmitters  306   a ,  306   b  and two 3 level PAM receivers  308   a ,  308   b . The 3 level PAM transmitters  306   a ,  306   b  may be electrically connected to the dual IO voltage supplies  218   a ,  218   b . In some embodiments, the dual IO voltage supplies  218   a ,  218   b  may be two dedicated IO voltage supplies  218   a ,  218   b . In some embodiments, the dual IO voltage supplies  218   a ,  218   b  may be a shared IO voltage supply  218   a  and a dedicated IO voltage supply  218   b . In some embodiments, the 3 level PAM transmitters  306   a ,  306   b  and 3 level PAM receivers  308   a ,  308   b  may be communicatively connected. 
     Via an input  316 , the encoder  302  may receive data and/or information for transmission as part of a memory transaction. The encoder  302  may receive the data and/or information as binary signals. The encoder  302  may encode the binary signals into transmitter input signals for generating 3 level PAM signals. For example, the encoder  302  may encode three binary signals into the transmitter input signals for two 3 level PAM transmitters  306   a ,  306   b . The transmitter input signals may be output by the encoder  302  to the 3 level PAM transmitters  306   a ,  306   b.    
     The 3 level PAM transmitters  306   a ,  306   b  may receive the transmitter input signals from the encoder  302 , and generate and output the 3 level PAM signals. The 3 level PAM transmitters  306   a ,  306   b  may include pre-drivers  310   a ,  310   b , pull up circuits  312   a ,  312   b ,  312   c ,  312   d , which are referred to herein as “pull ups,” and pull down circuits  314   a ,  314   b , which are referred to herein as “pull downs.” The pull ups  312   a ,  312   b ,  312   c ,  312   d  may be electrically connected to the dual TO voltage supplies  218   a ,  218   b . For example, the pull ups  312   a ,  312   b ,  312   c ,  312   d  may each be electrically connected to one of the dual TO voltage supplies  218   a ,  218   b , and the pull ups  312   a ,  312   b ,  312   c ,  312   d  of the same 3 level PAM transmitters  306   a ,  306   b  may each be electrically connected to a different one of the dual TO voltage supplies  218   a ,  218   b . As another example, the pull ups  312   a ,  312   c  may be electrically connected to the TO voltage supply  218   a , and the pull ups  312   b ,  312   d  may be electrically connected to the TO voltage supply  218   b . The pull downs  314   a ,  314   b  may be selectively electrically connected to the dual TO voltage supplies  218   a ,  218   b  via the pull ups  312   a ,  312   b ,  312   c ,  312   d . For example, the pull down  314   a  may be selectively electrically connected to the TO voltage supply  218   a  via the pull up  312   a  and selectively electrically connected to the TO voltage supply  218   b  via the pull up  312   b . The pull down  314   b  may be selectively electrically connected to the TO voltage supply  218   a  via the pull up  312   c  and selectively electrically connected to the TO voltage supply  218   b  via the pull up  312   d.    
     The 3 level PAM transmitters  306   a ,  306   b  may output the 3 level PAM signals via outputs  322   a ,  322   b . The outputs  322   a ,  322   b  may be selectively electrically connected to the dual IO voltage supplies  218   a ,  218   b  via the pull ups  312   a ,  312   b ,  312   c ,  312   d  and selectively electrically connected to ground via the pull downs  314   a ,  314   b . For example, the output  322   a  may be selectively electrically connected to the IO voltage supply  218   a  via the pull up  312   a , selectively electrically connected to the IO voltage supply  218   b  via the pull up  312   b , and selectively electrically connected to ground via the pull down  314   a . The output  322   b  may be selectively electrically connected to the IO voltage supply  218   a  via the pull up  312   c , selectively electrically connected to the IO voltage supply  218   b  via the pull up  312   d , and selectively electrically connected to ground via the pull down  314   b.    
     The pre drivers  310   a ,  310   b  may interpret the received transmitter input signals and accordingly control the pull ups  312   a ,  312   b ,  312   c ,  312   d  and the pull downs  314   a ,  314   b  to selectively electrically connect the outputs  322   a ,  322   b  to the dual IO voltage supplies  218   a ,  218   b  or ground to generate and output state signals. For example, the pre driver  310   a  may interpret the received transmitter input signals and accordingly control the pull ups  312   a ,  312   b  and the pull down  314   a  to selectively electrically connect the output  322   a  to the dual IO voltage supplies  218   a ,  218   b  or ground. The pre driver  310   b  may interpret the received transmitter input signals and accordingly control the pull ups  312   c ,  312   d  and the pull down  314   b  to selectively electrically connect the output  322   b  to the dual IO voltage supplies  218   a ,  218   b  or ground. 
     In some embodiments, the 3 level PAM transmitters  306   a ,  306   b  may generate and output up to nine state signals based on the selective connection of the outputs  322   a ,  322   b  to the dual IO voltage supplies  218   a ,  218   b  or ground. For example, each 3 level PAM transmitter  306   a ,  306   b  may generate and output three level signals (e.g., high “H”, medium “M”, and low “L”). The 3 level PAM signals output by each 3 level PAM transmitter  306   a ,  306   b  may be combined as any of the up to nine state signals. 
     The 3 level PAM receivers  308   a ,  308   b  may receive the 3 level PAM signals, and generate and output receiver output signals. The 3 level PAM receivers  308   a ,  308   b  may include comparator circuits  324   a ,  324   b ,  324   c ,  324   d  configured to compare the received 3 level PAM signals and voltage reference signals  326   a ,  326   b . For example, the comparator circuits  324   a ,  324   c  may be configured to compare whether states of the received 3 level PAM signals are less than the voltage reference signal  326   a . As another example, the comparator circuits  324   b ,  324   d  may be configured to compare whether states of the received 3 level PAM signals are less than, or greater than, the voltage reference signal  326   b . In such examples, the voltage reference signal  326   a  may be greater than the voltage reference signal  326   b . The results of the comparisons may prompt the comparator circuits  324   a ,  324   b ,  324   c ,  324   d  to output receiver output signals of values that represent the states of received 3 level PAM signals. 
     The decoder  304  may receive the receiver output signals from the 3 level PAM receivers  308   a ,  308   b , and generate and output data and/or information of the memory transaction. The decoder  304  may decode the receiver output signals to generate the binary signals as received by the encoder  302 . The decoder  304  may output the binary signals via an output  318 . 
     In some embodiments, the encoder  302  and the 3 level PAM transmitters  306   a ,  306   b  outputting the 3 level PAM signals, and the decoder  304  and the 3 level PAM receivers  308   a ,  308   b  receiving the 3 level PAM signals may be parts of different dual IO voltage 3 level PAM IO structures  300 . For example, the encoder  302  and the 3 level PAM transmitters  306   a ,  306   b  may be part of a memory physical layer, and the decoder  304  and the 3 level PAM receivers  308   a ,  308   b  may be part of an IO block. As another example, the encoder  302  and the 3 level PAM transmitters  306   a ,  306   b  may be part of an IO block, and the decoder  304  and the 3 level PAM receivers  308   a ,  308   b  may be part of a memory physical layer. 
       FIG.  4    illustrates an example dual IO voltage 3 level PAM timing diagram for implementing various embodiments. With reference to  FIGS.  1 - 4   , the timing diagram includes an IO voltage 1 (e.g., voltage of one of IO voltage supply  218   a ,  218   b  in  FIGS.  2 A- 3   ), an IO voltage 2 (e.g., voltage of the other of IO voltage supply  218   a ,  218   b  in  FIGS.  2 A- 3   ), a ground voltage (“GND”) (e.g., ground in  FIG.  3   ), a voltage reference  1  (“Vref  1 ”) (e.g., voltage of one of voltage reference signal  326   a ,  326   b  in  FIG.  3   ), and a voltage reference  2  (“Vref  2 ”) (e.g., voltage of the other of voltage reference signal  326   a ,  326   b  in  FIG.  3   ). 
     As described herein, a dual IO voltage 3 level PAM IO structure (e.g., dual IO voltage 3 level PAM IO structures  300  in  FIG.  3   ) may encode and output and/or receive and decode 3 level signals (e.g., high “H”, medium “M”, and low “L”). The value of a signal may depend on the control of the selective connections of 3 level PAM transmitters (e.g., 3 level PAM transmitters  306   a ,  306   b  in  FIG.  3   ) to IO voltage supplies (e.g., IO voltage supplies  218   a ,  218   b  in  FIGS.  2 A- 3   ). A high signal may result from selective electrical connection to a high IO voltage supply that may supply a high level voltage (“voltage 1”). A medium signal may result from a selective electrical connection to a low IO voltage supply that may supply a medium level voltage (“voltage 2”). A low signal may result from a selective electrical connection to ground. The dual IO voltage 3 level PAM IO structure may determine the type, value, level, or state of the 3 level PAM signal by comparison with Vref  1  and/or Vref  2 . For example, 3 level PAM receivers (e.g., 3 level PAM receivers  308   a ,  308   b  in  FIG.  3   ) of the dual IO voltage 3 level PAM IO structure may determine the type, value, level, or state of the 3 level PAM signal. 
     In some embodiments, the medium level voltage affects both high and medium signal timing and voltage margin. The low IO voltage supply level from a PMIC (e.g., PMIC  210  in  FIGS.  2   a   - 2 C) may be adjusted globally to balance between high and medium signal timing and voltage margin during Write &amp; Read data training in a computing device (e.g., computing device  10  in  FIG.  1   ). An SoC (e.g., SoC  12  in  FIG.  1   ) may provide certain control signals to the PMIC to adjust the low IO voltage supply. 
       FIG.  5    illustrate an example of 3 level PAM coding for implementing various embodiments. With reference to  FIGS.  1 - 5   , the table 500 illustrated in  FIG.  5    shows an example of potential mapping between binary signals and 3 level PAM signals for encoding and decoding between the binary signals and 3 level PAM signals by an encoder (e.g., encoder  302  in  FIG.  3   ) and a decoder (e.g., decoder  304  in  FIG.  3   ). The table 500 includes the binary signal values high “H” and low “L”, and the 3 level PAM signal values high “H”, medium “M”, and low “L”. In this example, three binary signals may each have one of two values for a total of eight possible combinations. The corresponding two 3 level PAM signals may each have one of three values. There may be nine possible combinations of 3 level PAM signals. However, the number of combinations of 3 level PAM signals is limited by the number of possible combinations of binary signals. Each combination of three binary signals may correspond to a combination of two 3 level PAM signals. In the illustrated example, the “HH” combination of 3 level PAM signals is omitted as it is the most power intensive. However, the claims and descriptions are not intended to be limited in scope by the example shown in  FIG.  5   . 
       FIGS.  6 A and  6 B  illustrate example dual IO voltage memory system interfaces for 3 level PAM IO schemes for implementing various embodiments. With reference to  FIGS.  1 - 6 B , a dual IO voltage memory system interface for 3 level PAM IO schemes  600   a ,  600   b  may be implemented by various components of a memory system (e.g., memory system  200   a ,  200   b ,  200   c  in  FIGS.  2 A- 2 C ). Such components may include a memory physical layer  206 , any number and combination of memory devices  208 , dual IO voltage supplies  218   a ,  218   b , and a communication bus (e.g., communication bus  220  in  FIGS.  2 A- 2 C ). In some embodiments, the communication bus may include any number and combination of data buses  602   a ,  602   b , data clock buses  604   a ,  604   b , read strobe clocks buses  606   a ,  606   b , a command and address bus  610 , a clock bus  612 , and data strobe buses  614   a ,  614   b.    
     The data buses  602   a ,  602   b  may vary in size. In some embodiments, the data buses  602   a ,  602   b  may be configured to transmit a same amount of data and/or information for a memory transaction as a single IO voltage memory system interface. In such embodiments, the dual IO voltage 3 level PAM IO scheme may encode more data per line of the data buses  602   a ,  602   b  based on having extra possible signal types, values, levels, or states. As such, the data buses  602   a ,  602   b  may be implemented with fewer lines compared to a single IO voltage memory system interface. For example, a data bus for a single IO voltage memory system interface may include eight binary data bit lines and binary function bit line (e.g., an error correction code parity bit line). Various binary bits may be encoded into fewer 3 level PAM signal bits, as described further herein. For example, three binary bits may be encoded as two 3 level PAM signal bits. Thus, nine binary bits may be reduced to six 3 level PAM signal bits and the number of lines of the data buses  602   a ,  602   b  may be reduced accordingly for a dual IO voltage memory system interface for 3 level PAM IO schemes  600   a ,  600   b.    
     In some embodiments, the data buses  602   a ,  602   b  may be configured to transmit more data and/or information for a memory transaction as a single IO voltage memory system interface. In other words, the data buses  602   a ,  602   b  may have a higher bandwidth. In such embodiments, the dual IO voltage 3 level PAM IO scheme may transmit more data over more lines of the data buses  602   a ,  602   b  without incurring extra power cost based on using lower power 3 level PAM signals than single IO voltage memory system interface. For example, a data bus for a single IO voltage memory system interface may include eight binary data bit lines and binary function bit line (e.g., an error correction code parity bit line). Various binary bits may be encoded into fewer 3 level PAM signal bits, as described further herein. For example, three binary bits may be encoded as two 3 level PAM signal bits. Thus, nine binary bits may be reduced to six 3 level PAM signal bits. The bandwidth of the data buses  602   a ,  602   b  may be doubled in comparison to the single IO voltage memory system interface by increasing the number of lines of the data buses  602   a ,  602   b  to twelve lines for a dual IO voltage memory system interface for 3 level PAM IO schemes  600   a ,  600   b.    
     In some embodiments, the dual IO voltage memory system interface for 3 level PAM IO schemes  600   a ,  600   b  may be configured for different clock schemes. For example, the dual IO voltage memory system interface for 3 level PAM IO schemes  600   a  illustrated in  FIG.  6 A  includes data clock buses  604   a ,  604   b  and read strobe clocks buses  606   a ,  606   b  of an LPDDR5 scheme. As another example, the dual IO voltage memory system interface for 3 level PAM IO schemes  600   b  illustrated in  FIG.  6 B  includes data strobe buses  614   a ,  614   b  of an LPDDR4 scheme. 
       FIG.  7    illustrates an example of signal allocations in a dual IO voltage memory system interface for 3 level PAM IO schemes for implementing various embodiments. With reference to  FIGS.  1 - 7   , example table 700, 702, 704 list signal allocations to data buses (e.g., communication bus  220  in  FIGS.  2 A- 2 C , data buses  602   a ,  602   b  in  FIGS.  6 A and  6 B ) in a dual IO voltage memory system interface for 3 level PAM IO schemes. As described herein, binary bits may be encoded into fewer 3 level PAM signal bits. As such, the data buses may be implemented with fewer lines compared to a single IO voltage memory system interface. Table 700 shows signal allocations of a burst of data of a memory transaction for a single IO voltage memory system interface using a nine line data bus. Table 702 shows signal allocations of a burst of data of a memory transaction for a dual IO voltage memory system interface for 3 level PAM IO schemes using a six line data bus. Table 704 shows the mapping between the lines of a data bus for single IO voltage memory system interface and the lines of a data bus for a dual IO voltage memory system interface for 3 level PAM IO schemes. Using the mapping shown in table 704, the comparison of table 700 and table 702 shows the signal allocation in tables 700 and 702 are for equivalent data bursts using different signaling and different size data buses. The signal allocation in table 702 allocates the equivalent data burst using fewer lines than the allocation in table 700. In the example in  FIG.  7   , the table 704 and the comparison of table 700 and 702 show a reduction ratio of 3:2. However, the claims and descriptions are not limited in scope by the example of  FIG.  7   . 
       FIG.  8    illustrates a method  800  for a method for dual IO voltage 3 level PAM IO according to an embodiment. With reference to  FIGS.  1 - 8   , the method  800  may be implemented in a computing device (e.g., computing device  10  in  FIG.  1   ), in software executing in a processor (e.g., processor  14 , in  FIG.  1   ), in general purpose hardware, in dedicated hardware (e.g., memory  16 ,  24  in  FIG.  1   , memory system  200   a ,  200   b ,  200   c , memory physical layer  206 , memory device  208 , IO block  212  in  FIGS.  2 A- 2 C , dual IO voltage 3 level PAM IO structure  300 , encoder  302 , decoder  304 , 3 level PAM transmitter  306   a ,  306   b , and 3 level PAM receiver  308   a ,  308   b , pre driver  310   a ,  310   b , comparator circuits  324   a ,  324   b ,  324   c ,  324   d  in  FIG.  3   ), or in a combination of a software-configured processor and dedicated hardware, such as a processor executing software within a memory power control system that includes other individual components, and various memory/cache controllers. In order to encompass the alternative configurations enabled in various embodiments, the hardware implementing the method  800  is referred to herein as a “dual IO voltage controller.” 
     In block  802 , dual IO voltage controller may receive a data signal. The data signal may be part of a received memory transaction from any number and combination of processors (e.g., processor  202   a ,  202   b ,  202   c  in  FIGS.  2 A- 2 C ). In some embodiments, the data signal may be a binary signal. In some embodiments, the dual IO voltage controller receiving the data signal in block  802  may be a memory physical layer, an IO block, and/or an encoder. 
     In block  804 , the dual IO voltage controller may encode the data signal as a transmitter input signal for generating a 3 level PAM signal and output the transmitter input signal. For example, the dual IO voltage controller may encode three binary signals into two groups of transmitter input signals for generating 3 level PAM signals. The binary signals may be represented by high and low values and the transmitter input signals may be translated as high, medium, and low signals. A combination of binary signal bits may be encoded into fewer 3 level PAM signals. In some embodiments, the dual IO voltage controller encoding the data signal as the transmitter input signal for generating a 3 level PAM signal and outputting the transmitter input signal in block  804  may be a memory physical layer, an IO block, and/or an encoder. 
     In block  806 , the dual IO voltage controller may receive and interpret the transmitter input signal. The transmitter input signals may be configured as control signals for selective electrical connection of an output of the dual IO voltage controller (e.g., output  322   a ,  322   b  in  FIG.  3   ) to dual IO voltage supplies (e.g., dual IO voltage supplies  218   a ,  218   b  in  FIGS.  2 A- 2 C and  3   ) and/or ground. In some embodiments, the dual IO voltage controller receiving and interpreting the transmitter input signal in block  806  may be a memory physical layer, an IO block, a 3 level PAM transmitter, and/or a pre driver. 
     In block  808 , the dual IO voltage controller may control a pull up unit(s) (e.g., pull up  312   a ,  312   b ,  312   c ,  312   d  in  FIG.  3   ) and/or a pull down unit (e.g., pull down  314   a ,  314   b  in  FIG.  3   ) to control receipt of voltage from the dual IO voltage supplies based on the transmitter input signal. The dual IO voltage controller may signal control signals to the pull up unit(s) to selectively electrically connect the output to the dual IO voltage supplies. The dual IO voltage controller may signal control signals to the pull down unit to selectively electrically connect the output to ground. The voltage received at the output in response to the selective electrical connection to the dual IO voltage supplies and/or ground may be a 3 level PAM signal derived from the data signal through encoding of the data signal to the transmitter input signal. In some embodiments, a signal state of the 3 level PAM signal may be high in response to selective electrical connection to a high IO voltage supply of the dual IO voltage supplies, medium in response to selective electrical connection to a low IO voltage supply of the dual IO voltage supplies, and low in response to selective electrical connection to ground. In some embodiments, the dual IO voltage controller controlling the pull up unit(s) and/or the pull down unit to control receipt of voltage from the dual IO voltage supplies based on the transmitter input signal in block  808  may be a memory physical layer, an IO block, a 3 level PAM transmitter, and/or a pre driver. 
     In block  810 , the dual IO voltage controller may output the 3 level PAM signal based on the voltage received from the IO voltage supply or ground according to the transmitter input signal. The dual IO voltage controller may output the 3 level PAM signal having a signal state resulting from the selective electrical connection of the output to the dual IO voltage supplies and/or ground via the pull up unit(s) and/or the pull down unit. In some embodiments, the dual IO voltage controller outputting the 3 level PAM signal based on the voltage received from the IO voltage supply or ground according to the transmitter input signal in block  810  may be a memory physical layer, an IO block, and/or a 3 level PAM transmitter. 
     In block  812 , the dual IO voltage controller may receive the 3 level PAM signal. The output 3 level PAM signal may be targeted to a receiving device based on the target of the memory transaction and/or return of the memory transaction. The target of the memory transaction and/or return of the memory transaction may receive the output 3 level PAM signal. In some embodiments, the dual IO voltage controller receiving the 3 level PAM signal in block  812  may be a memory physical layer, an IO block, a 3 level PAM receiver, and/or a comparator circuit. 
     In block  814 , the dual IO voltage controller may compare the 3 level PAM signal to a voltage reference (e.g., voltage reference signals  326   a ,  326   b  in  FIG.  3   ). For example, the dual IO voltage controller may compare whether the received 3 level PAM signal is less than a high voltage reference signal. As another example, the dual IO voltage controller may compare whether the received 3 level PAM signal is less than, or greater than, a low voltage reference signal. In such examples, the high voltage reference signal may be greater than the low voltage reference signal. In some embodiments, the dual IO voltage controller comparing the 3 level PAM signal to the voltage reference in block  814  may be a memory physical layer, an IO block, a 3 level PAM receiver, and/or a comparator circuit. 
     In block  816 , the dual IO voltage controller may generate and output the result of the comparison as a receiver output signal. The receiver output signal resulting from the comparison may be configured to describe the state of the received 3 level PAM signal. In some embodiments, the dual IO voltage controller generating and outputting the result of the comparison as the receiver output signal in block  816  may be a memory physical layer, an IO block, a 3 level PAM receiver, and/or a comparator circuit. 
     In block  818 , the dual IO voltage controller may receive and decode the receiver output signal as a data signal. The data signal resulting from decoding the receiver output signal may be the data signal received in block  802 . In some embodiments, the dual IO voltage controller receiving and decoding the receiver output signal as a data signal in block  818  may be a memory physical layer, an IO block, and/or a decoder. 
     In block  820 , the dual IO voltage controller may output the data signal. In some embodiments, the data signal may be output to a memory device. In some embodiments, the data signal may be output to a processor, such as via a memory controller. In some embodiments, the dual IO voltage controller outputting the data signal in block  820  may be a memory physical layer, an IO block, and/or a decoder. 
     Various embodiments (including, but not limited to, embodiments described above with reference to  FIGS.  1 - 8   ) may be implemented in a wide variety of computing systems including mobile computing devices, an example of which suitable for use with the various embodiments is illustrated in  FIG.  9   . The mobile computing device  900  may include a processor  902  coupled to a touchscreen controller  904  and an internal memory  906 . The processor  902  may be one or more multicore integrated circuits designated for general or specific processing tasks. The internal memory  906  may be volatile or non-volatile memory, and may also be secure and/or encrypted memory, or unsecure and/or unencrypted memory, or any combination thereof. Examples of memory types that can be leveraged include but are not limited to DDR, LPDDR, GDDR, WIDEIO, RAM, SRAM, DRAM, P-RAM, R-RAM, M-RAM, STT-RAM, and embedded DRAM. The touchscreen controller  904  and the processor  902  may also be coupled to a touchscreen panel  912 , such as a resistive-sensing touchscreen, capacitive-sensing touchscreen, infrared sensing touchscreen, etc. Additionally, the display of the mobile computing device  900  need not have touch screen capability. 
     The mobile computing device  900  may have one or more radio signal transceivers  908  (e.g., Peanut, Bluetooth, ZigBee, Wi-Fi, RF radio) and antennae  910 , for sending and receiving communications, coupled to each other and/or to the processor  902 . The transceivers  908  and antennae  910  may be used with the above-mentioned circuitry to implement the various wireless transmission protocol stacks and interfaces. The mobile computing device  900  may include a cellular network wireless modem chip  916  that enables communication via a cellular network and is coupled to the processor. 
     The mobile computing device  900  may include a peripheral device connection interface  918  coupled to the processor  902 . The peripheral device connection interface  918  may be singularly configured to accept one type of connection, or may be configured to accept various types of physical and communication connections, common or proprietary, such as Universal Serial Bus (USB), FireWire, Thunderbolt, or PCIe. The peripheral device connection interface  918  may also be coupled to a similarly configured peripheral device connection port (not shown). 
     The mobile computing device  900  may also include speakers  914  for providing audio outputs. The mobile computing device  900  may also include a housing  920 , constructed of a plastic, metal, or a combination of materials, for containing all or some of the components described herein. The mobile computing device  900  may include a power source  922  coupled to the processor  902 , such as a disposable or rechargeable battery. The rechargeable battery may also be coupled to the peripheral device connection port to receive a charging current from a source external to the mobile computing device  900 . The mobile computing device  900  may also include a physical button  924  for receiving user inputs. The mobile computing device  900  may also include a power button  926  for turning the mobile computing device  900  on and off. 
     The various embodiments (including, but not limited to, embodiments described above with reference to  FIGS.  1 - 8   ) may be implemented in a wide variety of computing systems include a laptop computer  1000  an example of which is illustrated in  FIG.  10   . Many laptop computers include a touchpad touch surface  1017  that serves as the computer&#39;s pointing device, and thus may receive drag, scroll, and flick gestures similar to those implemented on computing devices equipped with a touch screen display and described above. A laptop computer  1000  will typically include a processor  1002  coupled to volatile memory  1012  and a large capacity nonvolatile memory, such as a disk drive  1013  of Flash memory. Additionally, the computer  1000  may have one or more antenna  1008  for sending and receiving electromagnetic radiation that may be connected to a wireless data link and/or cellular telephone transceiver  1016  coupled to the processor  1002 . The computer  1000  may also include a floppy disc drive  1014  and a compact disc (CD) drive  1015  coupled to the processor  1002 . In a notebook configuration, the computer housing includes the touchpad  1017 , the keyboard  1018 , and the display  1019  all coupled to the processor  1002 . Other configurations of the computing device may include a computer mouse or trackball coupled to the processor (e.g., via a USB input) as are well known, which may also be used in conjunction with the various embodiments. 
     The various embodiments (including, but not limited to, embodiments described above with reference to  FIGS.  1 - 9   ) may also be implemented in fixed computing systems, such as any of a variety of commercially available servers. An example server  1100  is illustrated in  FIG.  11   . Such a server  1100  typically includes one or more multicore processor assemblies  1101  coupled to volatile memory  1102  and a large capacity nonvolatile memory, such as a disk drive  1104 . As illustrated in  FIG.  11   , multicore processor assemblies  1101  may be added to the server  1100  by inserting them into the racks of the assembly. The server  1100  may also include a floppy disc drive, compact disc (CD) or digital versatile disc (DVD) disc drive  1106  coupled to the processor  1101 . The server  1100  may also include network access ports  1103  coupled to the multicore processor assemblies  1101  for establishing network interface connections with a network  1105 , such as a local area network coupled to other broadcast system computers and servers, the Internet, the public switched telephone network, and/or a cellular data network (e.g., CDMA, TDMA, GSM, PCS, 3G, 4G, 5G, LTE, or any other type of cellular data network). 
     Computer program code or “program code” for execution on a programmable processor for carrying out operations of the various embodiments may be written in a high level programming language such as C, C++, C#, Smalltalk, Java, JavaScript, Visual Basic, a Structured Query Language (e.g., Transact-SQL), Perl, or in various other programming languages. Program code or programs stored on a computer readable storage medium as used in this application may refer to machine language code (such as object code) whose format is understandable by a processor. 
     Implementation examples are described in the following paragraphs. While some of the following implementation examples are described in terms of an example computing device memory system, further example implementations may include: the example functions of the computing device memory system discussed in the following paragraphs implemented as methods of the following implementation examples; and the example computing device memory system discussed in the following paragraphs implemented by a computing device memory system including means for performing functions of the computing device memory system of the following implementation examples. 
     Example 1. A computing device memory system, having a memory device, a memory physical layer communicatively connected to the memory device, a first input/output (TO) voltage supply electrically connected to the memory device and to the memory physical layer, and a second TO voltage supply electrically connected to the memory device and to the memory physical layer, in which the memory device and the physical layer communicate data of a memory transaction using a 3 level pulse amplitude modulation (PAM) TO scheme. 
     Example 2. The computing device memory system of example 1, in which the first TO voltage supply is a first dedicated TO voltage supply, and the second TO voltage supply is a second dedicated TO voltage supply. 
     Example 3. The computing device memory system of example 1, in which the first TO voltage supply is a dedicated TO voltage supply, and the second TO voltage supply is a shared TO voltage supply. 
     Example 4. The computing device memory system of any of examples 1-3, further including a first core voltage supply and a second core voltage supply, in which each of the first core voltage supply and the second core voltage supply are electrically connected to the memory device, and in which the shared TO voltage supply is electrically connected to the second core voltage supply. 
     Example 5. The computing device memory system of any of examples 1-4, further including a third core voltage supply, in which the third core voltage supply is electrically connected to the memory device, and in which a voltage of the second core voltage supply is greater than a voltage of the third core voltage supply. 
     Example 6. The computing device memory system of any of examples 1-3, further including a first core voltage supply, a second core voltage supply, and a third core voltage supply, in which each of the first core voltage supply, the second core voltage supply, and the third core voltage supply are electrically connected to the memory device, in which the shared TO voltage supply is electrically connected to the third core voltage supply, and in which a voltage of the second core voltage supply is greater than a voltage of the third core voltage supply. 
     Example 7. The computing device memory system of any of examples 1-5, in which a voltage of the second TO voltage supply is greater than a voltage of the first TO voltage supply. 
     Example 8. The computing device memory system of any of examples 1-7, in which the data of the memory transaction is binary data, and the memory device and the memory physical layer further convert between the binary data and 3 level PAM IO scheme signals using the first TO voltage supply and the second TO voltage supply. 
     Example 9. The computing device memory system of any of examples 1-8, in which the memory device encodes the data of the memory transaction for generating a 3 level PAM signal, and generates the 3 level PAM signal by controlling selective electrical connection of the first TO voltage supply, the second TO voltage supply, or a ground to a component of the memory device according to the encoded data. 
     Example 10. The computing device memory system of any of examples 1-9, in which the memory physical layer encodes the data of the memory transaction for generating a 3 level PAM signal, and generates the 3 level PAM signal by controlling selective electrical connection of the first TO voltage supply, the second TO voltage supply, or a ground to a component of the memory physical layer according to the encoded data. 
     The foregoing method descriptions and the process flow diagrams are provided merely as illustrative examples and are not intended to require or imply that the operations of the various embodiments must be performed in the order presented. As will be appreciated by one of skill in the art the order of operations in the foregoing embodiments may be performed in any order. Words such as “thereafter,” “then,” “next,” etc. are not intended to limit the order of the operations; these words are simply used to guide the reader through the description of the methods. Further, any reference to claim elements in the singular, for example, using the articles “a,” “an” or “the” is not to be construed as limiting the element to the singular. 
     The various illustrative logical blocks, modules, circuits, and algorithm operations described in connection with the various embodiments may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and operations have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the claims. 
     The hardware used to implement the various illustrative logics, logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Alternatively, some operations or methods may be performed by circuitry that is specific to a given function. 
     In one or more embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a non-transitory computer-readable medium or a non-transitory processor-readable medium. The operations of a method or algorithm disclosed herein may be embodied in a processor-executable software module that may reside on a non-transitory computer-readable or processor-readable storage medium. Non-transitory computer-readable or processor-readable storage media may be any storage media that may be accessed by a computer or a processor. By way of example but not limitation, such non-transitory computer-readable or processor-readable media may include RAM, ROM, EEPROM, FLASH memory, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of non-transitory computer-readable and processor-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a non-transitory processor-readable medium and/or computer-readable medium, which may be incorporated into a computer program product. 
     The preceding description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the claims. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and implementations without departing from the scope of the claims. Thus, the present disclosure is not intended to be limited to the embodiments and implementations described herein, but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.