Patent Publication Number: US-2023153256-A1

Title: Method and devices for controlling operations of a central processing unit

Description:
This application is a continuation of U.S. patent application Ser. No. 17/485,808, filed Sep. 27, 2021, which is a continuation of U.S. patent application Ser. No. 16/811,201, filed Mar. 6, 2020 (now U.S. Pat. No. 11,138,138), which is a continuation of U.S. patent application Ser. No. 15/866,760, filed Jan. 10, 2018 (now U.S. Pat. No. 10,592,449), which is a continuation of U.S. patent application Ser. No. 15/157,676, filed May 18, 2016 (now U.S. Pat. No. 9,898,429), which is a continuation of U.S. patent application Ser. No. 14/588,643, filed Jan. 2, 2015 (now U.S. Pat. No. 9,355,047), which is a continuation of U.S. patent application Ser. No. 13/324,164, filed Dec. 13, 2011 (now U.S. Pat. No. 8,930,737), the entire contents of which are hereby incorporated by reference in this application. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a method and devices for controlling operations of a Central Processing Unit (CPU), and more particularly it relates to a control circuitry configured to interact with the Central Processing Unit. 
     BACKGROUND 
     The roll out of Internet and the following continuous investment in infrastructure providing network access to the Internet have made information exchange easy throughout the globe. With the global access to all sorts of different computer systems the Internet provides for and the increasing use of the Internet, the numbers of data messages directed to central computer servers of the computer systems are increasing. Many computer systems are connected to the Internet to provide access to functionalities for a select group of people or for the public. Depending on the functionalities and the interest people have in accessing the functionalities, different computer systems receive different amounts of data messages. 
     An automated electronic exchange is one such type of computer system wherein users of the automated electronic exchange in one way or another connect to a central computer server which is part of the automated electronic exchange, usually through the Internet, and submit data messages to the central computer server. 
     Due to technological advances in computing technology, transaction technology and information technology in the past ten to twenty years, financial technology has had a very rapid development rate. This rapid development has resulted in computer systems trying to cope with increasing numbers of companies and people trying to connect to these systems. The increasing numbers of users being connected to electronic exchange systems have increased the amount of data messages sent into the system. 
     A conventional electronic exchange typically receives input data in the form of data messages from external devices, trader terminals, used by traders to send orders and/or quotes to the electronic exchange. The orders/quotes may relate to buying and/or selling of any type of tradable asset. In particular the input data can relate an order message that represents the placing of a new buy or sell order or a new quote. Furthermore, the development of algorithmic trading, i.e. computers programmed to analyze data and autonomously act on the data by submitting orders to an electronic exchange, has exponentially increased the amount of data messages being sent to the electronic exchange systems. 
     In order for computer systems to perform some kind of action in response to the data messages sent by users of the computer system the data messages have to be received in some kind of input/output device and detected as input. 
     Traditionally one way of detecting a data message input in a computer system has been to do it in an interrupt driven process. Input received by an input/output (I/O) device of the computer server of the computer system has triggered an interrupt request to be issued. A central processing unit (CPU) of the computer system typically breaks (interrupts) its current computations and stores the current state when receiving the interrupt request. The CPU then processes a set of stored instructions related to the specific interrupt request. When all instructions related to the interrupt request have been completed, the CPU reverts back to the stored state and continues processing the set of instructions it was processing prior to the interrupt request. The transition between states of processing in the CPU is typically called a context switch. When no interrupt request is received by the CPU, or when the CPU is finished with the current processing, the CPU can revert to an idle mode. 
     Another technique to detect input to a computer system is to have the CPU poll an I/O device for input, i.e. continuously check the I/O device until input is found, and then process the input when a poll renders input. 
     The interrupt driven detection and handling of input has the advantage that the CPU when not processing input can process other instructions. The polling technique has the advantage that input generally is detected and processed earlier as the CPU expects to find and is ready to process any input each poll (check) of the I/O device might render. 
     A disadvantage with the interrupt driven technique is that, when receiving huge amounts of data messages for computer systems requiring a high throughput, the interrupt driven process may be experienced as giving rise to a too high latency. Latency is defined as the time from an input data message is received by the computer system until the computer system has completed processing the data message and is ready receive a new data message. The interrupt driven techniques is therefore less suitable for systems with low latency requirements. 
     A disadvantage with the polling technique is that, while it allows for a low latency system, there is a risk that the CPU is constantly working at full load just polling the I/O device even at times when there is no input to retrieve. For most computer systems, the data messages do not arrive in a steady stream but the amount of data messages directed towards the computer system varies quite a lot over time with peaks and troughs. Thus while, the polling techniques are suitable for periods with peak load, polling for input is not particularly suitable for periods of trough load as large numbers of polls resulting in no input have to be performed, so-called negative polls. The negative polls of the polling techniques cause unnecessarily high processing load as well as energy consumption of the CPU. 
     For many computer systems a swift change in load is a problem, for automated electronic exchanges it is a particular problem. Since information is easily spread globally, many users of an automated electronic exchange tend to act on the same information at almost the same time. Therefore peaks often are concentrated around occasions when information, that in one way or another might change the appreciation made by users connected to the automated electronic exchange, is released somewhere in the world. 
     The number of data messages directed toward the automated electronic exchanges, hence shifts very drastically between peaks and troughs throughout a trading day. 
     It would thus be advantageous to provide a more flexible and efficient way of processing input received in a computer system. 
     SUMMARY 
     An object of the embodiments of the present invention is to provide a method and apparatus that allow a CPU to process input in a flexible and efficient way. 
     The above stated object is achieved by a method, a control circuitry and a computer server according to the independent claims. 
     A first embodiment provides, a method for controlling the operations of a Central Processing Unit (CPU) associated with a nominal clock frequency. The CPU is coupled to an input/output (I/O) range and configured to deliver input to an application. The method comprises controlling the CPU to poll the I/O range for input to the application. The polling is repeated until a poll results in input to the application. The method further comprises monitoring whether or not each poll results in input to the application and adjusting a clock frequency at which the CPU operates, to a predetermined first clock frequency lower than the nominal clock frequency, if a pre-defined number of polls resulting in no input is detected. 
     A second embodiment provides a control circuitry for controlling a CPU associated with a nominal clock frequency. The CPU is coupled to an I/O range and configured to deliver input received at the I/O range to an application. The control circuitry is arranged to instruct the CPU to poll the I/O range for input to the application and to monitor whether or not a poll results in input to the application. The control circuitry is further arranged to adjust a clock frequency at which the CPU operates, to a predetermined first clock frequency lower than the nominal clock frequency, if a pre-defined number of polls of the I/O range resulting in no input is detected. 
     A third embodiment provides a central computer server of an automated exchange system for matching orders received from clients. The central computer server comprises an I/O range for receiving orders from clients in the automated exchange system and a CPU associated with a matching process for matching received orders. The CPU is coupled to the I/O range. The central computer server further comprises a control circuitry in accordance with the second embodiment described above for controlling the CPU to poll the I/O range for received orders for input to the matching process. 
     An advantage of some of the embodiments disclosed herein is that processing by a CPU can be performed with lower energy consumption while providing for rapid response to input. These and other aspects and advantages of different embodiments will become apparent from the following detailed description and from the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following description of embodiments of the invention, reference will be made to the accompanying drawings of which: 
         FIG.  1    is a flow diagram illustrating an embodiment of a method for controlling operations of a CPU. 
         FIG.  2    is a flow diagram illustrating an alternative embodiment of a method for controlling operations of a CPU. 
         FIG.  3    is a flow diagram illustrating another alternative embodiment of a method for controlling operations of a CPU. 
         FIG.  4    is a schematic block diagram illustrating a computer server comprising a CPU and a control circuitry according to an example embodiment. 
         FIG.  5    is a schematic illustration of an automated exchange system including an embodiment of an automated exchange. 
         FIG.  6    is a schematic block diagram illustrating a layered topology of data processing in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Some example embodiments will now be described in more detail with use of the figures. 
     Depending on the use and configuration of a computer system different capabilities are provided and also required of it. For computer systems processing input data in a Central Processing Unit (CPU) it is typically advantageous to detect and process data as quickly as feasible in order to potentially be able to service as many inputs as possible. As described above it is of interest that the CPU processes input in a flexible and efficient way. Embodiments to be described in further detail below achieve this by controlling the operations of the CPU by use of a frequency adjusting control circuitry. By controlling the operations of the CPU as well as the frequency at which the CPU operates advantageous effects in regards to thermal energy, processing power, latency and throughput can be achieved. 
       FIG.  1    is a flowchart illustrating an example embodiment of a method for controlling operations of a CPU. The example method is adapted for use in a control circuitry for controlling the operations of the CPU. The CPU is associated with a nominal clock frequency. The CPU is further coupled to an input/output, I/O, range and configured to deliver input to an application. The application may be practically any type of application program processing input, such as an order matching process of an automated exchange system. 
     For illustrative purposes below, it is envisaged that the operating frequency of the CPU when the method is initialized, is the nominal clock frequency. However, the actual configuration and architecture of a particular system will of course determine an actual operating frequency for the particular system. 
     The method outlined in  FIG.  1    in step  110 , comprises controlling the CPU to poll the I/O range for input to the application. The method further comprises a step  120  of monitoring whether or not each poll results in input to the application. If it is detected in the step  120  that a poll results in input to the application, the CPU is controlled to return the input to the application in a step  190 . If a poll is a negative poll, i.e. results in no input to the application, it is determined in a step  130 , if a pre-defined number (X) of negative polls have been detected. 
     The number of consecutive negative polls may for example be counted by incrementing an accumulator register of the CPU for each negative poll. The accumulator register may also, when a poll is positive i.e. renders input to the application, be reset. The accumulated number of consecutive negative polls may then be compared to the pre-defined number. When it is detected that the pre-defined number of consecutive negative polls has been performed, the frequency at which the CPU operates is adjusted to a pre-determined first clock frequency lower than the nominal clock frequency in a step  140 . Assuming that the CPU operated at the nominal clock frequency when the method was initiated, performing the step  140  will thus lead to a reduction of the clock frequency at which the CPU operates. In a step  150  the CPU is controlled to again poll for input to the application, which thus is carried out at the reduced frequency following the step  140 . As a consequence the CPU will continue to poll the I/O range for input to the application less frequently, which reduces the processing load as well as energy consumption of the CPU. When a poll at the reduced frequency results in input to the application, the CPU is controlled to return the input to the application in the step  190 . Thus, according to the example method illustrated in  FIG.  1   , the CPU is controlled to repeat the polling until a poll results in input to the application. But the frequency at which this polling is carried out may be changed depending on the amount of detected negative polls. 
     The pre-defined number of negative polls to be detected before an adjustment of the operating frequency of the CPU can be set to any number which is considered appropriate in the particular application scenario as a trigger for adjusting down the operating frequency. The number which is considered appropriate may depend on the type of system employing the method and also on a tradeoff between thermal efficiency and input detection speed. By allowing a higher number of negative polls before adjusting down the operating frequency, a high detection speed can be achieved at the risk of worse long term thermal efficiency. However, if thermal efficiency is more important a smaller number of negative polls should be allowed before adjusting the operating frequency. The pre-defined number may be optimized based on the expected load of the system and the requirements put on the system. 
     In an example embodiment, the operating frequency is reduced directly after detecting a single negative poll. The configuration of the pre-defined number to one has the advantage that it results in a high thermal efficiency. Hence in some embodiments, the pre-defined number equals one. In these embodiments the number of negative polls may be kept low by continuing polling at a reduced speed as soon as a negative poll is detected. The total amount of energy the CPU wastes on negative polls may thus also be kept low. At the same time the system still allows for a high throughput as latency is not increased when a positive poll is followed by another positive poll 
     By reducing the clock frequency at which the CPU operates the amount of negative polls can be kept down to assure that the CPU is not wasting energy by just polling for input when no input is available. However, the processing by the CPU of any received input at the reduced frequency will lead to increased latency in comparison to the CPU operating at the nominal frequency. The latency is increased as each clock cycle used to process the input is longer. Therefore it is advantageous to increase the operating frequency of the processor for every input detected when the processor is operating at the reduced clock frequency. Hence, according to some example embodiments, the method illustrated in  FIG.  1    further comprises an optional step  180  in which the clock frequency at which the CPU operates is adjusted to a predetermined second clock frequency higher than the reduced clock frequency set in the step  140 . The step  180  is performed if it is detected in the step  160  that a poll results in input to the application. 
     In some embodiments, the predetermined second clock frequency equals the nominal clock frequency in other embodiments the predetermined second clock frequency is higher than the nominal clock frequency. By increasing the operating frequency of the CPU, to the nominal clock frequency associated with the CPU, the processing of a received input can be performed using less time. The increase of the operating frequency thus leads to reduced latency than if processed while the processor operates at the reduced frequency. As increased operating frequency leads to reduced latency it is further advantageous to increase the operating frequency of the CPU to a frequency higher than the nominal clock frequency associated with the CPU. This may be possible for a limited period if the CPU e.g. has been cooling down by operating at the reduced frequency for some time as will be further explained below in connection with another example embodiment. 
     In some embodiments the polling is performed in response to reception of an instruction from the application, step  100 . The instruction may also specify to poll the I/O range for input to the application until a poll results in input to the application. 
     In some embodiments the control circuitry is also configured to detect polling of an I/O range. The control circuitry is configured to monitor read operations on the I/O range and a poll resulting in no input is detected by detecting a return to the same instruction to read the I/O range within a pre-determined number of instructions. 
       FIG.  2    is a flowchart illustrating some procedural steps of a so-called implicit method according to an example embodiment. The method is referred to as an implicit method since there is no reception of an explicit instruction to poll the I/O range as in the method illustrated in  FIG.  1   . While an application in the embodiment described in  FIG.  1    typically issues an explicit poll instruction, this may not always be the case. Some applications may, instead of an explicit poll instruction to the CPU, be configured to perform polling and control the polling within the application program code. For example, an application may be configured to repeatedly read a certain I/O port or an I/O range until input is found, thus implicitly performing polling. Hence in some embodiments including the method in the example embodiment of  FIG.  2   , polling is instead detected. 
     In the example embodiment, a control circuitry controls the operations of a Central Processing Unit (CPU) associated with a nominal clock frequency. The CPU is coupled to an input/output (I/O) range and configured to deliver input to an application. The method comprises a step  200  of detecting polling of an I/O range for input to the application. 
     In the step  210 , a predetermined number of polls not resulting in input, i.e. negative polls are detected. This is achieved by the control circuitry monitoring whether or not each poll results in input to the application. In some embodiments, the polling of an I/O range is detected by the control circuitry monitoring read operations on the I/O range, and a poll resulting in no input is detected by detecting a return to the same instruction to read the I/O range within a predetermined number of instructions. 
     On detecting the predefined number of negative polls the clock frequency at which the CPU operates, is in the step  220  adjusted down to a predetermined first clock frequency lower than the nominal clock frequency, i.e. to a reduced clock frequency. 
     Some embodiments of the method illustrated in  FIG.  2    also comprises a step  230  of detecting a positive poll, i.e. a poll rendering input to the application, by monitoring the outcome of each poll while the CPU is operating at the reduced frequency. On detecting a positive poll, the operating frequency of the CPU is, in a step  240 , adjusted up to a second predetermined clock frequency. 
     By detecting the polling of an I/O range the implicit method allows applications programmed to, for example, poll an I/O range by issuing read operations to also benefit from the method. Thus, even older applications not configured for requesting polling from a CPU may benefit from the claimed invention. In some embodiments, the monitoring of read operations on the I/O range may be limited to a particular I/O port, I/O address or an I/O sub range, typically assigned to the reception of input in order to speed up the monitoring and detection process. 
     Some CPUs allow “overclocking” (n.b. operating a CPU at a frequency higher than the associated nominal clock frequency) or some other method of boosting the operations of the CPU. The method of the example embodiment illustrated in  FIG.  3    is particularly suited for use with CPUs suitable for “overclocking”. 
       FIG.  3    is a flow diagram illustrating a further example embodiment of a method for controlling operations of a CPU. The method of  FIG.  3    bears similarities with some of the method steps disclosed in  FIG.  1   , in particular steps  100 - 160  are similar and will not be described in detail again. 
     In a step  370  the method determines, when a poll results in input in either of the steps  120  or  160 , a temperature of the CPU. 
     In another step  375  of the method, the temperature of the CPU is compared against a predefined temperature threshold. By the comparison, it is possible to detect if the CPU thermally is able to cope with a temporary boost in operating frequency without it leading to overheating of the CPU. In a step  380  the clock frequency at which the CPU operates is adjusted to a predetermined third clock frequency higher than the nominal frequency, if the temperature of the CPU is below the temperature threshold. Typically, operating a CPU above the nominal clock frequency is not sustainable over time, due to overheating of the CPU. However, as the disclosed method reduces the operating frequency of the processor below the nominal clock frequency on detecting a predetermined number of negative polls, the temperature of the CPU might allow the CPU for a short time to operate at a frequency higher than the nominal clock frequency associated with the processor without causing problems related to overheating. 
     In a further step  390  the CPU is controlled to return the detected input in either of step  120  or step  150  to the application. 
     When polling for input instead of using an interrupt driven process, the CPU continuously tries to check the I/O range for input as often as possible. The CPU thus works at full capacity polling for input. Typically the nominal clock frequency associated with the CPU is a frequency at which the manufacturer guarantees that the CPU sustainably can operate at full load. By, in step  370 , measuring a temperature of the processor on receiving and detecting input to be processed, it is possible to determine if the CPU recently have been operating at or close to a maximum sustainable operating frequency. If it is determined, in step  375 , that the CPU have been operating below the maximum sustainable clock frequency of the CPU, a short period of increased operation and the following increased heat generation might be allowable. If on the other hand, in step  375 , it is determined that the CPU have been operating above the maximum sustainable operating frequency of the CPU, an increase of the operating frequency to a third operating frequency higher than the nominal clock frequency might lead to instability. Hence, by comparing the measured CPU temperature against a predetermined threshold value suitable for the CPU in step  375  it is possible to determine if it is wise to increase the operating frequency of the CPU to a predetermined third frequency higher than the nominal clock frequency. If the measured temperature is determined to be below the threshold value it is possible to increase the operating frequency and reduce the latency, to allow the input to be processed faster. 
     If it is detected in step  375  that the temperature of the CPU is above the threshold value, it might not be wise to adjust the operating frequency of the CPU to a frequency higher than the nominal clock frequency. The nominal clock frequency is typically associated with a sustainable operating frequency and in some embodiments the clock frequency at which the CPU operates is adjusted to the nominal clock frequency in step  380  if the temperature is not below the temperature threshold. 
     However in some embodiments, an increase of the operating frequency above nominal operating frequency might momentarily be justifiable even if the CPU temperature surpasses the threshold temperature. For example, it might be justifiable for a predetermined number of consecutive positive polls. The increase of operating frequency may for example also, be justifiable for a predefined number of clock cycles or for the processing of a predefined number of instructions in the CPU. 
     While  FIG.  3    illustrates the step  100 , where an explicit poll instruction is received, it should be understood that steps  370 - 390 , could be combined with the implicit method of detecting polling and the alternative way of detecting positive and negative polls disclosed above in regards to  FIG.  2   . 
     It should also be understood that a system configured to perform more than one of the above example embodiments may be created. 
       FIG.  4    illustrates an example embodiment of a computer server  400  comprising a CPU  410  and a control circuitry  420 . In  FIG.  4    only the elements necessary for the invention are disclosed. It should, however, be understood that the computer server  400  of  FIG.  4    may comprise further elements and the disclosed elements may be part of, or comprise, further elements. For example, the computer server typically comprise some persistent storage like an hard disk drive and a data bus for interconnecting some of the elements with each other (neither explicitly disclosed in the figure). The computer server  400  also comprises a memory unit  450 , or storage medium, comprising an application  440 ; and an Input/output (I/O) range  430  associated with at least one I/O device (the device not explicitly shown in  FIG.  4   ) for receiving input. 
     The application  440  is a set of computer readable instructions to be executed in the CPU  410 . 
     The memory  450 , while illustrated and referenced below as one memory, can comprise a set of memories. The memory  450  typically stores computer instructions which are to be executed. The memory unit  450  is typically a Random Access Memory (RAM), a Read Only Memory (ROM) or a non-volatile memory unit. In some embodiments of the present invention the storage medium is a CD-rom disk, a blue-ray disk, a HDD (hard disc drive), a USB (Universal Serial Bus) unit connected to the computer server  400  or one of the many other means suitable for storing computer readable instructions. 
     Typically each I/O device comprises a range of I/O ports of which at least one is addressed for each I/O operation directed at the device. In general, each of the I/O ports of the I/O devices within the computer server is “numbered” to distinguish each I/O port from every other I/O port. The number which identifies a particular I/O port is often called its address. The computer server  400  may support Direct Memory Access (DMA) technique. The DMA technique allows for I/O devices to write and read data directly to and from the memory  450 , via the data bus, surpassing the CPU  410 . Typically, in order to support DMA the I/O device(s) and corresponding I/O ports(s) are mapped to a particular section of the memory. The CPU  410  when instructed to read (or write to) the I/O device in such an instance typically reads (or writes to) the parts of the memory that the I/O port(s) on the I/O device are mapped onto. 
     The CPU  410 , when executing an I/O read (or write) operation, typically addresses one or more I/O port(s) of the I/O device but may for I/O operations also, as described above, address a section of the memory, when I/O ports are mapped to the memory  450 . The term I/O range is herein used to interchangeably refer to: a single I/O port, multiple I/O ports or a set of memory address wherein each address corresponding to a section of the memory when I/O devices are mapped the memory; for which input can be expected to be received or found (when mapped). 
     In the example embodiment illustrated in  FIG.  4   , the CPU  410 , in order to perform a particular I/O operation, thus locates and addresses the I/O range  430  corresponding to the intended I/O ports of the I/O device to be affected by the particular operation. 
     In the example embodiment of  FIG.  4    the CPU comprises the control circuitry  420 . In some alternative embodiments the control circuitry  420  is not part of the CPU  410  but is instead comprised in the computer server  400  and coupled to the CPU  410  as indicated by an alternative dashed control circuitry. 
     The CPU  410  is associated with a nominal clock frequency and the control circuitry  420  is arranged to control the CPU  410 . The CPU  410  is further coupled to an I/O range  430  and configured to deliver input received at the I/O range  430  to an application  440 . The control circuitry  420  is arranged to instruct the CPU  410  to poll the I/O range  430  for input to the application. 
     The control circuitry  420  is also arranged to monitor whether or not a poll results in input to the application  440 . The control circuitry  420  is further arranged to adjust the clock frequency at which the CPU  410  operates based on the result of the polling operation in accordance with one or several of the method steps  140 ,  180 ,  220 ,  240 ,  380  described above and illustrated in  FIGS.  1 ,  2  and  3    respectively. 
     By monitoring whether or not each poll results in input, a number of consecutive polls rendering the same result can be detected. For example a predefined number of consecutive polls rendering no input, negative polls, may be detected. When detecting that a predefined number of consecutive negative polls have come to pass, the clock frequency fed to the CPU is adjusted down to a predetermined first clock frequency lower than the nominal clock frequency. The continued polling for input will then be performed at a frequency below the nominal frequency. As a result fewer negative polls will be detected for each period of time. 
     The pre-defined number of polls allowed before the clock frequency at which the CPU operates is adjusted down is preferably chosen in accordance with the requirements of a particular implementation as described above in relation to the methods illustrated in  FIGS.  1 - 3   . 
     In some embodiments, the CPU  410  is configured to receive, from the application  440  an instruction to poll the I/O range  430  until a poll results in input to the application. The CPU  410  is further arranged to poll the I/O range  430  in response to reception of the instruction from the application  440 . 
     In some embodiments the control circuitry  420  is configured to control the CPU  410  to poll the I/O range  430  in response to reception of an instruction from the application  440  to poll the I/O range  430  for input to the application until a poll results in input to the application. 
     In some embodiments, the control circuitry  420  is arranged to monitor whether or not a poll results in input to the application by monitoring read operations on the I/O range  430 . 
     In some embodiments, the control circuitry  420  is configured to detect polling of the I/O range  430 . The control circuitry is further arranged to detect a poll resulting in no input by being arranged to detect, within a predetermined number of instructions following a performed read operation on the I/O range  430 , a return to the same instruction to read the I/O range  430 . 
     In some embodiments, the control circuitry  420  is further arranged to adjust the clock frequency at which the CPU  410  operates, in accordance with one or several of the steps  180 ,  240  described above and illustrated in  FIGS.  1  and  2   , to a predetermined second clock frequency, when a poll results in input to the application  440 . 
     In order to allow for low latency, when a poll actually results in input, the clock frequency at which the CPU operates is in some embodiments increased to a predetermined second frequency. In some embodiments, the predetermined second clock frequency equals the nominal clock frequency. 
     In some embodiments the predetermined second clock frequency is higher than the nominal clock frequency. Typically the polling at a frequency lower than the nominal clock frequency consumes less energy than polling at the nominal frequency. Thus, in situations where a number of consecutive negative polls higher than the pre-defined number of polls have been performed and the operating frequency is reduced, less heat will have been induced in the CPU. The CPU can in such situations for a short time be allowed to operate at a frequency higher than the nominal clock frequency. This provides for a more thermally efficient system where energy and heat generation is focused on situations where there is input to process. 
     In some embodiments the control circuitry  420  is also arranged to perform the steps  370 - 380  described above and illustrated in  FIG.  3   . Thus, for some embodiments, the control circuitry  420  is further arranged to determine, when a poll results in input, a temperature of the CPU  410 ; and to compare the temperature of the CPU against a predefined temperature threshold. The control circuitry  420  is further configured to adjust the clock frequency at which the CPU  410  operates to a predetermined third clock frequency higher than the nominal clock frequency, if the temperature of the CPU is below the temperature threshold. 
     In situations where the temperature of the CPU can be determined to be less than a pre-defined temperature threshold, the operating frequency of the CPU can be increased to a predetermined third clock frequency higher than the nominal clock frequency in order to reduce latency when processing a received input. 
     In situations where the temperature of the CPU is above or equal to the temperature threshold, operation of the CPU at a frequency higher than the nominal clock frequency may lead to overheating. In some embodiments, the control circuitry  420  is arranged to adjust the clock frequency at which the CPU  410  operates to the nominal clock frequency if the temperature is not below the temperature threshold. 
     In some embodiments, which are further elaborated on below in regards to  FIG.  6   , the CPU is arranged to poll the I/O range  430  by bypassing an operating system kernel of the CPU  410 . By letting the application, through the use of a hardware instruction library, poll the I/O range directly the latency can be further reduced. 
       FIG.  6    illustrates a layered topology of data processing in accordance with some embodiments.  FIG.  6    is to some extent an alternative or complementary illustration of the computer server  400  illustrated in  FIG.  4   . Both the application layer and the kernel layer in  FIG.  6    relates to processing done in a CPU  410  of a computer server. Typically an application  640  when executed in the CPU  410  interacts with an operating system, (OS) being executed in the CPU  410 . The processing in the CPU  410  prompted by the application is in  FIG.  6    represented by the application layer. The application  640  corresponds to application  440  in  FIG.  4   . The OS is not explicitly disclosed in  FIG.  6   ; however, the processing prompted by the OS is in  FIG.  6    represented by the kernel layer. The main component of the operating system is typically referred to as an OS kernel. The OS kernel provides a bridge between the application  640  and the actual data processing in peripheral hardware devices  644  of the computer. Examples of such peripheral hardware devices  644  are an InfiniBand (IB) I/O controller card and a gigabit Ethernet I/O controller card, but could be any type of network adapter or network interface card. Peripheral hardware devices  644  used for input and output are below referenced as peripheral I/O devices. Each peripheral I/O device is associated with at least one I/O port, and any subset of all the I/O ports of all the peripheral I/O devices, could constitute an I/O range similar to the I/O range  430  previously disclosed in  FIG.  4   . 
     In the following OS and OS kernel is interchangeably used when referring to the operating system (while the OS not explicitly disclosed in  FIG.  6   , the processing by the OS is in  FIG.  6    represented by the kernel layer). The application  640  requesting resources or communicating with a peripheral device  644  (in hardware layer) is not required to have explicit knowledge of the peripheral device&#39;s  644  characteristics. The OS kernel typically has a device driver installed for all connected peripheral hardware devices  644 . When the OS kernel receives instructions from the application  640 , the OS kernel translates the instructions into instructions comprehendible by the peripheral device  644 . Vice versa the OS can translate instructions/data from the peripheral hardware device  644  into a format comprehendible by the application  640 . Double arrows  643  schematically illustrate a path through which the application  640  normally interacts with peripheral hardware devices  644 . In order for the CPU  410  to switch between processing in application layer and processing in kernel layer a context switch is required. 
     While accessing system I/O resources typically is done through calls from the application  640  to the operating system kernel and induces at least one context switch, it is possible for the application  640  to comprise hardware instructions that are acceptable to peripheral I/O devices  644 . The application  640  in application layer can, by comprising a hardware instruction library  641  with instructions suitable for a particular peripheral I/O device  644  in hardware layer, interact with the particular peripheral I/O device  644  directly as schematically illustrated by a double arrow  642  in  FIG.  6   , i.e. surpassing the kernel layer. 
     Sometimes it is advantageous to bypass an operating system when performing certain I/O tasks in order to further reduce the latency and increase the throughput of a computer system. By bypassing the operating system kernel, the application  640  with the use of the hardware instruction library  641  can control the CPU  410  to poll an I/O range  430 . By configuring the application through the use of a hardware instruction library to poll the I/O range directly, no context switch between the application and the OS kernel in the CPU  410  is necessary for the polling and the latency can be further reduced. Thus, in some embodiments, the CPU  410  is arranged to poll the I/O range  430  by bypassing an operating system kernel of the CPU  410 . 
     An additional advantage of the disclosed method and the control circuitry is the ability to detect polling and detect a predetermined number of negative polls which allows the control circuitry to control the operations of the CPU regardless if the computer architecture allows an application to bypass an operating system. 
       FIG.  5    illustrates an example embodiment of an automated exchange system  500  comprising trader terminals  560  that are used for issuing order data messages, i.e. input data, from clients to a central computer server, i.e. an automated exchange,  400  operating in accordance with one of the above disclosed methods. The automated exchange  400  may e.g. be embodied in accordance with the example computer server  400  illustrated in  FIG.  4   . The trader terminals  560  are connectable, for example over the Internet  580 , or over some other connection means like a dedicated fiber  580 B, to the automated exchange  400 . The automated exchange  400  of  FIG.  5    may in some embodiments be embodied as a cluster of automated exchanges. Sometimes the trader terminals  560  are connected to the automated exchange  400  through an entry gateway  570 . The entry gateway  570  is connected to the central computer server hosting the automated exchange  400 , and is configured to receive market actions, i.e. orders and/or quotes from the trader terminals  560 . An entry gateway  570  is usually in connection with the automated exchange  400  on a dedicated network and forwards the market actions to the automated exchange  400  and further usually broadcast updates back to the trader terminals  560 . It should however be understood that information being communicated to and from the automated exchange  400  and the trader terminals  560  could be communicated via a single communication path. Typically, the automated exchange  400  matches the orders received from the trading terminals in a matching process. The matching process of the automated exchange  400  is one typical implementation of the application  440  in  FIG.  4   . 
     As mentioned above, the automated exchange  400  may be embodied in accordance with the example computer server illustrated in  FIG.  4   . For this particular embodiment the central computer server  400  of the automated exchange system  500  in  FIG.  5   , expressed in terms of the functional units of  FIG.  4   , comprises an input/output, I/O, range  430  for receiving orders from trader terminals  560 . The central computer server also includes a CPU  410 , coupled to the I/O range  430 , and a control circuitry  420 . The CPU  410  of the central computer server is associated with a matching process for matching received orders, corresponding to the application  440  of  FIG.  4   . The matching process  440  is arranged to control the CPU  410  of the central computer server to poll said I/O range  430  for received orders for input to the matching process  440 . 
     The central computer server of an automated exchange system (i.e. the automated exchange) comprising a control circuitry in accordance with embodiments described herein has the advantage that incoming input (i.e. orders) can be detected and processed at an earlier stage than with an interrupt driven process. The central computer server also has the advantage that during troughs in load the automated exchange wastes less clock cycles on negative polls. The reduced number of negative polls leads to a more energy efficient server. Some embodiments of the computer server also have the advantage that as soon as an order is received and detected, the central computer server is ready to process the order at nominal clock frequency, thus allowing for a high throughput and a low latency. A central computer server of the present invention may thus allow for a low latency and energy efficient automated exchange suitable for high throughput. 
     An advantage of certain embodiments described above is that incoming input, such as orders to an automated exchange, can be detected and processed at an earlier stage than with an interrupt driven process. Another advantage of some of the embodiments is that that during troughs in load less clock cycles are wasted. Hence by reducing the number of negative polls the system becomes more energy efficient. A further advantage of some of the embodiments is that as soon as an order is received and detected the central computer server is ready to process the order at nominal clock frequency, thus allowing for a high throughput and a low latency. An additional advantage of some of the embodiments is that the energy consumption is reduced by polling at a reduced frequency. By operating the CPU at a reduced frequency less electrical energy is also converted in thermal energy, allowing for the operating frequency of the CPU to be increased above the nominal operating frequency when processing a received input. This may in turn allow for latency to be reduced considerably and throughput to be increased while maintaining a stable system. 
     The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appended claims.