# Patent

## Title
Supply margining method and apparatus

## Abstract

In accordance with some embodiments, margining routines to determine acceptable voltage command values for specific CPU implementations at one or more different operating levels may be provided.

## Background
CLAIM OF PRIORITY
The present application is a Continuation of, and claims priority to and incorporates by reference, the corresponding U.S. patent application Ser. No. 12/060,057 filed Mar. 31, 2008, and entitled “SUPPLY MARGINING METHOD AND APPARATUS,” and issued as U.S. Pat. No. 8,601,292 on Dec. 3, 2013.


BACKGROUND
FIG. 1 shows a conventional implementation of a voltage regulator 102 coupled to a CPU 104 to provide it with a regulated voltage supply VR. The CPU requests a desired voltage by way of a voltage identification (VID) command to the VR 102. The voltage that it actually receives (Vin), however, will be less than that generated by the VR due to a voltage drop across the loadline, represented by resistor block R. This resistance includes the output resistance from the voltage regulator, as well as resistances from the connections (pins, contacts, traces, etc.) from the regulator to the CPU.
The loadline resistance determines droop voltages for currents between minimum and maximum CPU loads. It also affects CPU maximum frequency (performance) and maximum efficiency voltage/frequency. Accordingly, to ensure that the CPU can work adequately over expected temperature and process ranges of deviations, from device to device and environment to environment, a VID guardband is typically used to account for the worst-case loadline. Unfortunately, this can result in wasted power and/or lower maximum attainable performance. Thus, improved approaches would be desired.



BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements.
FIG. 1 is a diagram of a conventional arrangement of a voltage regulator coupled to supply power to a CPU.
FIG. 2 is a diagram of a voltage regulator and a CPU with a margining routine in accordance with some embodiments.
FIG. 3A shows a margining routine for setting a voltage regulator and CPU combination to operate under maximal (or near maximal) load conditions in accordance with some embodiments.
FIG. 3B is a flow diagram of a margining routine for determining operating limits for minimal (or near minimal) load conditions in accordance with some embodiments.
FIG. 4 is a diagram of a voltage regulator with a CPU having a voltage sensor for implementing a margining routine in accordance with some embodiments.
FIG. 5 is a margining routine in accordance with additional embodiments.
FIG. 6 is a diagram of a multi-domain regulator supplying power to a multi-core CPU having margining capabilities in accordance with some embodiments.
FIG. 7 is a side view of a multi-domain regulator and multi-core CPU package in accordance with some embodiments.
FIG. 8 is a diagram of a portion of a computer system with a CPU and voltage regulator with margining capability in accordance with some embodiments.



DETAILED DESCRIPTION
CPUs typically allocate voltage guardbands, on the upper end to avoid (or reduce) damage due to overshoot, and on the lower end to thwart system hang due to undershoot. The guardband normally takes into account worst case CPU and VR process, voltage, and temperature. In reality, however, in many situations, the actual worst case values for each component will rarely occur. It is even less likely that both worst cases will occur at the same time. Thus, better, more particularized guardband values for upper and/or lower operating load conditions can be attained and used for individual systems for their particular application workloads and environments.
In accordance with some embodiments, margining routines to determine acceptable voltage command values for specific CPU implementations at one or more different operating levels may be provided. For example, a margining routine may achieve enhanced performance from a voltage regulator that can provide sufficiently responsive operating parameters. With additional embodiments, margining routines to determine one or more guardband values for specific implementations may also be provided. With some of these embodiments, voltage regulators may be driven harder and/or power may be saved by not having to request excess supply voltage therefrom.
FIG. 2 shows a voltage regulator 202 coupled to a CPU 204 to provide it with a regulated voltage supply (VR), although the CPU actually receives a lesser voltage (Vin) due to the drop across the loadline R. Also shown is the SVID bus for the CPU to request a desired voltage and for receiving one or more operating parameter(s) (also referred to as telemetry information) from the regulator. A controller 206, such as a baseboard management controller (BMC), is controlled to issue a command to the CPU 204 to cause it to execute a margining routine 208 to determine appropriate VID levels based on monitored operating parameters.
In some embodiments, the voltage regulator 202 is an integrated switching type regulator, e.g., a multi-phase switching buck-type regulator, with enough of its switching devices (transistors), inductors and capacitors integrated into a common package. With such sufficient integration, the switches may be switched at very high frequencies, e.g., in excess of 50 MHz. This allows for the operating parameter(s), e.g., supplied current, temperature, power, and the like, to be highly responsive to changes in the parameters. For example, operating parameter data may be responsive in excess of 200 nSec. sampling intervals. In turn, this allows for the margining routine 208 (through the CPU 204 or controller 206) to push CPU performance to the brink of the voltage regulator's capabilities. FIG. 3A shows a margining routine 208A for setting a voltage regulator and CPU combination to operate under maximal (or near maximal) load conditions, while FIG. 3B is a margining routine 208B for determining operating (e.g., VID) limits for minimal (or close to minimal) load conditions.
FIG. 3A shows a flow diagram of a margining routine 208 suitable for use, among other places, with the CPU 204 from FIG. 2. With this embodiment, an objective is to determine an extreme upper operating level for the VR in combination with the CPU in its given environment. The VR maker may establish maximum operating parameters such as short term and extended duration power, current, temperature, and the like. Traditionally, it (or another entity such as a PC maker) may have used a general VID guardband that ensured these parameters would not be exceeded. However, with more responsive parameter information from the VR such as described above, this guardband may effectively be “squeezed” for a given configuration and particularly squeezed even further for a given operating environment.
At 302, an initial VID and Frequency are set, and the CPU is driven with suitable software, e.g., suitable work load or benchmark application. In some embodiments, for example, the VID and frequency could be set to a Max Non-Turbo state. Regardless, in most situations, the value should be sufficiently low for encountered devices (e.g., being tested, adjusted, and/or verified) so that it doesn't start off with operating VR parameters exceeding specified limits. For example, with a CPU rated to operate up to 100 W at voltages ranging from 1.1 to 1.5 V, the initial VID might be for 1.3V with a load (determined by frequency and received Vin) of about 90 W.
At 304, the CPU (or test equipment through CPU and/or controller) monitors the VR operating parameters. For example, it could monitor any suitable combination of maximum voltage, thermal, TDP, TDC limits. At 306, if they are not exceeded, then the routine goes to 310 and increases the load (e.g., VID and/or frequency) and loops back to 304.
On the other hand, if at 306, it determines that the operating parameter(s) are exceeded, then it proceeds to 308 and saves the load (e.g., VID and/or frequency) value(s) (settings or setting) as a maximum operating load value(s). For this step, the value(s) may be burned into one or more fuses or stored in suitable non-volatile memory.
FIG. 3B shows a margining routine for determining a minimum load margin in accordance with some embodiments. At 322, an initial load is set. For example, the VID and frequency could be at a max. efficiency setting. The CPU can be driven with any suitable software such as a work load or benchmark application. At 324, the supplied voltage is monitored. This could be the VR voltage monitored from received VR parameter(s) or from a measured voltage, e.g., in the CPU.
At 326, it determines if the min. voltage limit is reached. If not, it proceeds to 330 and decreases the load (e.g., decreases VID and frequency) an from there, loops back to 324. Otherwise, it goes to 328 and saves the load setting (e.g., VID and frequency) as a minimum load setting.
FIG. 4 shows another embodiment of a VR (402) and CPU (404) configuration. In this embodiment, the CPU comprises a margining routine 408. The voltage sensor 406 in the CPU 404 measures the regulated voltage received at the CPU. With such a voltage sensor, it can measure the received supply VIN, downstream from the loadline, so that a guard band better suited for a particular implementation can be determined, thereby allowing for the VID guard band to be reduced for most devices. This can save power at both the upper and lower ends of a CPU's operating voltage range. FIG. 5 is a margining routine 408 for determining acceptable VID values or ranges for a particular CPU and VR configuration, e.g., in a given environment, in accordance with some embodiments. Initially, at 502, a VID is set for a given performance level, e.g., with a certain CPU frequency, voltage, and processing task. Next, the received supply voltage (Vin) is determined (e.g., measured from voltage sensor 406). Next, at 506, a guard band for these values is determined based on the difference between the requested V R and received Yin. This determined guard band (or difference) is associated and saved with the VID and/or performance level used for the determination.
At 508, the routine determines if it is done. For example, it could check to see if enough values over a wide enough range have been obtained, or another approach could be used. If it is not finished, then it proceeds to 510 and adjusts the VID and/or performance level. From here, it returns to 504 and executes as already discussed.
Thus, with this routine, many different data points can be taken over a range of performance levels and over a range of VID levels. On the other hand, it could be use to determine guardband for a limited range, e.g., upper VID levels, e.g., at demanding performance states or lower VID levels at lower performance states. In addition, the measured and/or determined (calculated, estimated, etc.) guardband levels for use in later operation can be determined in many different ways. For example, over the range of different values obtained from the routine just described, a worse-case value could be used, or alternatively, different values could be used (e.g., by way of a look-up table) for different operating steps (or sub-ranges).
FIG. 6 shows an embodiment of an integrated voltage regulator 601 coupled to a multi-core CPU 610. Integrated Silicon Voltage Regulator (ISVR) technology involves the integration of a voltage regulator into the package. This includes the magnetic, capacitance, power switches, controllers, telemetry, and interfaces. Embodiments disclosed herein can be used with the ISVR telemetry (operating parameters) for dynamically adjusting the CPU loadline to save power during normal operation.
FIG. 6 shows an embodiment of a multi-cell IVR 601 coupled to a multi-core CPU 610 to provide it with regulated voltage supplies for associated cores (611i) in a multi-core processor 610. The multi-cell IVR 601 has multiple VR domains 604 (6041 to 604N), for example, each comprising multiple cells and being coupled to an associated core 611i (6111 to 611N) in the CPU 610. The IVR 601 also has a master controller 602 to control the IVR domains 604 to enable and disable cells within the domain based on information from the core loads, as well as from a power control unit (PCU) 613 in the CPU 610, which issues VID commands and receives operating parameter information for the separate core/domain combinations.
In some embodiments, the IVR 601 and processor 610 may be part of a common package, such as with the embodiment of FIG. 7, discussed below. With the dies from the VR and processor mounted proximal to one another, circuit elements for VR domains can be disposed more proximal to their associated core. This can allow for sufficiently low-resistive paths (e.g., via solder bumps or other contacts) to conduct relatively large amounts of current to the domain cores. Also, in some embodiments, the magnetic elements, capacitors, power switches, controllers, interfaces, and even telemetry elements (sensors, analog or digital signal lines, etc.) to provide the operating parameters are contained within the same package, which among other things, allows for greater switching speeds and thus, increased telemetry (operating parameter) responsiveness. It also provides for the operating parameter signals to be more accurate because the interconnectivity can be shorter and subject to a more stable temperature environment (e.g., changes similarly within VR and CPU).
FIG. 7 shows a cross-sectional view of a multi-core microprocessor (such as the processor of FIG. 6) integrated circuit (IC). It comprises a multi-cell integrated voltage regulator (IVR) die 701 and a multi-core microprocessor die 710 coupled together as shown. The IVR die 701 is embedded within a package substrate 720, while the microprocessor die is mounted to the substrate 720 and against the IVR die 701 for efficient signal connectivity. In this embodiment, the substrate 720 serves as a package substrate for both the processor 610 and IVR 601. Note that the dies may or may not actually contact one another. They may have one or more other materials sandwiched between them throughout some or all of their abutting surface portions. Such materials could be used for structural stability, heat transfer purposes, power and signal grids, or the like. Moreover, it should be appreciated that any suitable package configuration using one or more dies to implement the domain cores and VR may be implemented and are within the scope of the present invention. For example, the IVR die could be “atop” the microprocessor die instead of “below” it. Alternatively it could be next to it, partially against it, or they could be part of the same die.
With reference to FIG. 8, one example of a portion of a computer platform (e.g., computing system such as a desktop or server computer, PDA, cell phone, or the like) is shown. The represented portion comprises one or more CPU's 810, integrated voltage regulator (IVR) 801, control interface 820, memory 825, I/O devices 830, and monitor 835, coupled as shown. The CPU 810 is coupled to the memory 825, I/O devices 830, and monitor 835 through the control interface 820. The CPU comprises a margining routine 818, as discussed herein, to determine particular VID ranges and/or values for a particular computing platform implementation. The control interface may comprise one or more circuit blocks to perform various interface control functions (e.g., memory control, graphics control, I/O interface control, and the like. These circuits may be implemented on one or more separate chips and/or may be partially or wholly implemented within the CPU 810.
The memory 825 comprises one or more memory blocks to provide additional random access memory to the CPU 810. It may be implemented with any suitable memory including but not limited to dynamic random access memory, static random access memory, flash memory, combinations of the same, or the like. The I/O devices comprise any devices such as keyboards, mousse, printers, audio input/output devices and the like to allow a user to input data into and perceive data out from the CPU 810. The monitor 835 may comprise any monitor such as a liquid crystal display (LCD) or the like for presenting a visual image to a user.
In the preceding description, numerous specific details have been set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques may have not been shown in detail in order not to obscure an understanding of the description. With this in mind, references to “one embodiment”, “an embodiment”, “example embodiment”, “various embodiments”, etc., indicate that the embodiment(s) of the invention so described may include particular features, structures, or characteristics, but not every embodiment necessarily includes the particular features, structures, or characteristics. Further, some embodiments may have some, all, or none of the features described for other embodiments.
In the preceding description and following claims, the following terms should be construed as follows: The terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, “connected” is used to indicate that two or more elements are in direct physical or electrical contact with each other. “Coupled” is used to indicate that two or more elements co-operate or interact with each other, but they may or may not be in direct physical or electrical contact.
The invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. For example, it should be appreciated that the present invention may be applicable for use with all types of semiconductor integrated circuit (“IC”) chips. Examples of these IC chips include but are not limited to processors, controllers, chip set components, programmable logic arrays (PLA), memory chips, network chips, and the like.
It should also be appreciated that in some of the drawings, signal conductor lines are represented with lines. Some may be thicker, to indicate more constituent signal paths, have a number label, to indicate a number of constituent signal paths, and/or have arrows at one or more ends, to indicate primary information flow direction. This, however, should not be construed in a limiting manner. Rather, such added detail may be used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit. Any represented signal lines, whether or not having additional information, may actually comprise one or more signals that may travel in multiple directions and may be implemented with any suitable type of signal scheme, e.g., digital or analog lines implemented with differential pairs, optical fiber lines, and/or single-ended lines.
It should be appreciated that example sizes/models/values/ranges may have been given, although the present invention is not limited to the same. As manufacturing techniques (e.g., photolithography) mature over time, it is expected that devices of smaller size could be manufactured. In addition, well known power/ground connections to IC chips and other components may or may not be shown within the FIGS., for simplicity of illustration and discussion, and so as not to obscure the invention. Further, arrangements may be shown in block diagram form in order to avoid obscuring the invention, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements are highly dependent upon the platform within which the present invention is to be implemented, i.e., such specifics should be well within purview of one skilled in the art. Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the invention, it should be apparent to one skilled in the art that the invention can be practiced without, or with variation of, these specific details. The description is thus to be regarded as illustrative instead of limiting.

## Claims

1. An apparatus, comprising:
a voltage regulator operable with first voltage guardband values associated with upper and lower limits of a voltage command value; and
a processor to be coupled to the voltage regulator to provide it with a voltage command and to receive a supply voltage corresponding to the commanded voltage and to receive operating parameter information from the voltage regulator, the processor to determine allowable voltage command values for later operation based on operating parameters from the voltage regulator,
wherein the processor is operable to determine second voltage guardband values associated with upper and lower limits of the allowable voltage command values,
wherein the second voltage guardband values are determined based on a difference between the received supply voltage and a requested supply voltage, and
wherein the first voltage guardband values are higher than the second voltage guardband values.

2. The apparatus of claim 1, wherein the voltage regulator is an integrated voltage regulator with a semiconductor die, switching elements, and magnetic components integrated into a common package.

3. The apparatus of claim 1, wherein the voltage regulator when operated is switched in excess of 10 MHz.

4. The apparatus of claim 1, wherein the operating parameter information includes regulator information with responsiveness of at least 200 nano-seconds.

5. The apparatus of claim 1, wherein the processor is controlled by an external controller to determine the allowable voltage command values.

6. The apparatus of claim 1, wherein the voltage regulator and processor are part of a common package.

7. An apparatus, comprising:
a computer having a processor and a voltage regulator to provide the processor with a regulated received voltage in response to a voltage command for a commanded voltage, wherein the regulated received voltage has a voltage level which is less than a voltage level of the commanded voltage during processor operation;
logic for determining voltage command guardband information corresponding to one or more differences between values of the received voltage and commanded voltage under different test conditions; and
a memory for storing the voltage command information and the determined voltage command guardband information for later use by the processor.

8. The apparatus of claim 7, wherein the voltage command guardband information comprises guardband values determined for separate commanded voltages at different processor performance levels.

9. The apparatus of claim 7, wherein the guardband information comprises voltage command values.

10. The apparatus of claim 7, wherein the processor comprising logic for receiving operating parameter information from the voltage regulator and for determining voltage command guardband information based on said operating parameter information.

11. A system comprising:
a memory;
a voltage regulator operable with first voltage guardband values associated with upper and lower limits of a voltage command value;
a processor coupled to the memory, the processor to be coupled to the voltage regulator to provide it with a voltage command and to receive a supply voltage corresponding to the commanded voltage and to receive operating parameter information from the voltage regulator, the processor to determine allowable voltage command values for later operation based on the operating parameters from the voltage regulator,
wherein the processor is operable to determine second voltage guardband values associated with upper and lower limits of the allowable voltage command values and
wherein the second voltage guardband values are determined based on a difference between the received supply voltage and a requested supply voltage, and
wherein the second voltage guardband values are lower than the first voltage guardband values; and

a wireless interface for allowing the processor to communicate with another device.

12. The system of claim 11, wherein the voltage regulator is an integrated voltage regulator with a semiconductor die, and wherein switching elements and magnetic components associated with the voltage regulator are integrated into a common package.

13. The system of claim 11, wherein the voltage regulator when operated is switched in excess of 10 MHz.

14. The system of claim 11, wherein the operating parameter information includes regulator information with responsiveness of at least 200 ns.

15. The system of claim 11, wherein the processor is controlled by an external controller to determine the allowable voltage command values.

16. The system of claim 11, wherein the voltage regulator and processor are part of a common package.

17. The apparatus of claim 1, wherein the voltage regulator to dynamically adjust load-line of the processor to save power during normal operation.

18. The apparatus of claim 1, wherein the voltage regulator comprises at least two voltage regulator domains to provide at least two voltage supplies to the processor.

19. The apparatus of claim 18, wherein the processor comprises at least two processor cores to receive the at least two voltage supplies, respectively.

20. The apparatus of claim 1, wherein the processor includes a storage medium for saving the second guardband values and associated performance level of the processor.