Classifications

• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
  • G06F1/26—Power supply means, e.g. regulation thereof
  • G06F1/32—Means for saving power
  • G06F1/3203—Power management, i.e. event-based initiation of a power-saving mode
  • G06F1/3234—Power saving characterised by the action undertaken
  • G06F1/325—Power saving in peripheral device
  • G06F1/3275—Power saving in memory, e.g. RAM, cache
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F13/00—Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
  • G06F13/38—Information transfer, e.g. on bus
  • G06F13/40—Bus structure
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F12/00—Accessing, addressing or allocating within memory systems or architectures
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F13/00—Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
  • G06F13/14—Handling requests for interconnection or transfer
  • G06F13/16—Handling requests for interconnection or transfer for access to memory bus
  • G06F13/1668—Details of memory controller
  • G06F13/1689—Synchronisation and timing concerns
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F13/00—Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
  • G06F13/38—Information transfer, e.g. on bus
  • G06F13/40—Bus structure
  • G06F13/4063—Device-to-bus coupling
  • G06F13/4068—Electrical coupling
  • G06F13/4072—Drivers or receivers
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F13/00—Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
  • G06F13/38—Information transfer, e.g. on bus
  • G06F13/40—Bus structure
  • G06F13/4063—Device-to-bus coupling
  • G06F13/4068—Electrical coupling
  • G06F13/4086—Bus impedance matching, e.g. termination
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F13/00—Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units
  • G06F13/38—Information transfer, e.g. on bus
  • G06F13/42—Bus transfer protocol, e.g. handshake; Synchronisation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
  • Y02D10/00—Energy efficient computing, e.g. low power processors, power management or thermal management

Definitions

• This invention relates to memory subsystems including physical layers that directly interface with dynamic random access memory (DRAM) devices.
• DRAM dynamic random access memory
• Typical memory systems use either an asynchronous or synchronous clocking scheme to transmit data between the memory controller and the memory device.
• Synchronous clocking means that the memory device waits for a clock signal before responding to control inputs and is therefore synchronized with the computer's system bus.
• Synchronous dynamic random access memory (SDRAM) is widely used since such devices typically support higher clock speeds than asynchronous memory devices.
• Double data rate (DDR) SDRAM transfers data on both the rising and falling edges of the clock signal.
• Such memory devices use a lower clock frequency but require strict control of the timing of the electrical data and clock signals.
• the first version of such devices (DDR1) achieved nearly twice the bandwidth of a single data rate (SDR) SDRAM running at the same clock frequency.
• DDR2 and DDR3 SDRAM devices are subsequent improvements over DDR1 devices.
• a physical interface (Phy) is coupled directly between the memory controller and the DDR SDRAM devices.
• the Phy interface generally includes circuitry for handling the timing requirements of the DDR SDRAM
• a physical memory interface (Phy) is provided.
• the Phy interfaces between a memory controller and physical memory devices.
• the Phy interface includes command and status registers (CSRs) configured to receive a first power context and second power context.
• CSRs command and status registers
• Selection circuitry is provided.
• the selection circuitry is configured to switch between the first and second power contexts.
• the Phy interface includes a plurality of adjustable delay elements, each having a delay time responsive the selected power context. Switching between power contexts results in an adjustment of one or more of the adjustable delay elements.
• the Phy interface includes a first set of
• the Phy interface may also include a plurality of drivers each having a selectable drive strength responsive to the selected power context.
• the Phy interface may also include a plurality of receivers each having a selectable termination impedance responsive to the selected power context. Switching between power contexts may result in adjusting of the drive strength and/or termination impedance of one or more drivers/receivers.
• the first and second power context may be determined via a
• BIOS training procedure Such procedures may have multiple phases.
• the first power context may be determined via a first memory training phase and the second power context may be determined via a second memory training phase.
• the Phy interface may include a configuration bus that is configured to allow read/write access the CSRs.
• the Phy interface may also be configured to support multiple channels of physical memory devices.
• 1308878-4 interface may be located in various locations including on a die of a central processing unit (CPU).
• CPU central processing unit
• Figure 1 shows a portion of a typical computer system
• Figure 2 shows the high level architecture of Phy
• Figure 3 is a timing diagram showing the address, command
• Figure 4 shows a breakdown CSRs addressing.
• Figure 1 shows a portion of a computer system 10 including a central processing unit (CPU) 12, a core logic chipset 14, 16 and memory interface 18 to main memory 28.
• the core logic chipset may be divided between a north bridge 14 (or integrated memory controller) and a south bridge (or I/O controller hub) 16.
• the memory controller 18 is often located in the north bridge 14. It should be understood that such circuitry may be physically located in a variety of locations such as a single chip or in the CPU.
• the memory controller 18 generally manages the logical flow of data going to and from main memory 30. Dynamic random access memory also requires periodic refresh signals to maintain the charge in the various memory storage cells. The memory controller 18 typically manages these refresh operations.
• main memory 30 may transfer data in 32 or 64 bit data units. It should be understood that other size data units may be supported.
• Some memory systems include multiple channels (e.g., two or more independent memory controllers) as reflected by blocks 20, 24 and 30. For purposes of clarity, the examples contained herein may illustrate only a single memory channel. It should be understood that multiple channels may be used without departing from the scope of this disclosure.
• a Phy interface 22 resides between the memory controller 18 and the physical memory devices.
• the Phy interface is typically located in the central processing unit but may be located elsewhere.
• the Phy interface 22 is shown as a separate block in Figure 1.
• the Phy interface generally includes circuitry for handling the timing requirements of the main memory data strobes.
• double data rate encompasses DDR1 / DDR2 / DDR 3 and/or subsequent generations of such memory devices.
• DDR memory devices typically conform to Joint Electron Devices Engineering Councils (JEDEC) standards. These standards define how DDR memory data is accessed (read), and stored (written).
• a Phy interface may be constructed to operate with other memory types and/or other memory standards.
• the interface to a typical DDR SDRAM memory device is accomplished primarily through two signal classes, DQ (data) 32 and DQS (data strobe) 34.
• Other signals include the memory clock (MEMCLK) 38 as well as address and command signals (shown generally as ADDR/CMD 36).
• MEMCLK memory clock
• ADDR/CMD 36 address and command signals
• typical memory devices may use additional signals that are not shown in the drawing figures. Such signals have been omitted for purposes of clarity only. For example, power and ground signals are not shown. It should be understood that such signals would be included in a typical implementation.
• a DDR SDRAM issues DQ and DQS at the same time, a manner commonly referred to as "edge aligned."
• the Phy interface 22 utilizes delay circuitry, such as a delay-locked loop (DLL), to delay the DQS signal so that it may be used to correctly latch the DQ signals during a valid data window or "data eye”.
• the Phy interface 22 also utilizes delay circuitry to support the writing of data to the DDR DRAM.
• the DQS 34 For reading data, the DQS 34 must be delayed.
• the DQS and DQ 34, 32 must be delayed. The Phy aligns DQS 34 with the middle of the DQ 32 data eye rather than edge aligned. DQS 34 is delayed
• the Phy interface 22 includes a plurality of command and status registers (CSRs) 42 that are utilized to control delay timing, drive strengths and a variety of other parameters as described in more detail below. It should be understood that such circuitry may be duplicated on a per channel basis as well.
• CSRs command and status registers
• the Phy interface may also adjust or select transmitter drive strength and receiver termination impedance. Rather than use fixed timing delays, transmitter drive strength and receiver termination impedance, these parameters may be adjusted each time the computer system is turned on. This is typically accomplished with the assistance of a training program.
• the training program is typically stored in a basic input/output system (BIOS) memory device 26, but it may also be implemented within the device hardware.
• BIOS basic input/output system
• the training program executes an algorithm during power-on self- test (POST), which determines appropriate timing delays, drive strengths and termination impedances associated with many of the memory interface signals.
• POST power-on self- test
• Theses parameters are saved within the Phy interface in a plurality of registers that define the overall timing of the various signal paths to and from the Phy. In the alternative, these parameters may be stored elsewhere (e.g., in the north bridge 14 or south bridge 16).
• Figure 2 shows the high level architecture of the Phy interface
• the Phy interface generally includes a clock source (e.g., PLL 70) and a control interface that includes command and status registers (CSR) 42.
• the Phy interface 20 provides physical connections for a majority of the pins on a typical memory device such as a dual in-line memory module (DIMM) including DQ 32, DQS 34, address/command lines 36 and clock input 38.
• DIMM dual in-line memory module
• Typical memory devices are also provided with a clock enable
• the clock enable input 40 is used to place the memory device in self refresh mode. In this mode, the memory device uses an on-chip timer to generate internal refresh cycles as necessary. External clocks may
• 1308878-4 also be stopped during this time. This input is typically used in connection with power down modes since it allows the memory controller to be disabled without loss of main memory data.
• the DQ 32 (data) and DQS 34 (strobe) lines are bidirectional. It should be understood that each DIMM will have multiple DQ lines (e.g., 64 data bits) and multiple DQS lines. Each of these lines has an associated driver 52, 56 and receiver 54, 58 in the Phy interface 22. A single driver/receiver pair is shown in Figure 2 for purposes of clarity. Each driver has a selectable or adjustable drive output. Similarly, each receiver has a selectable or adjustable termination impedance (e.g., on die termination).
• the DQ and DQS lines 32, 34 are also associated with delay elements such as delay locked loops (DLLs) 72, 74, 76.
• DLLs delay locked loops
• Adjustments to delay elements are accomplished via programming appropriate values into the proper field of an associated CSR 42 as described in more detail below.
• the logical connection between CSRs and adjustments in delay elements, drive strength or termination impedance are shown generally in dashed lines.
• drivers 52 and 56 are associated with DLLs 72 and 74 respectively.
• Receiver 58 is associated with DLL 76.
• the DLLs are adjusted to provide the appropriate timing delays for read and write operations.
• the Phy interface may also be configured to perform read and write operations with or without leveling. During memory write operations to DDR3 DIMMS with leveling, the Phy interface delays the launch of each DQS going to the DIMM such that at each DRAM chip DQS is seen to coalesce with the memory clock 58. During read operations with leveling, the Phy interface may also compensate delays introduced by fly-by topology.
• the Phy interface may dynamically change the DLL settings on a burst-by- burst (or transaction) basis.
• the Phy interface may store an optimum tupple of delay settings for DQ and DQS for each DIMM in the system. Depending upon
• the Phy interface retrieves the appropriate DLL settings and applies them.
• the Phy interface may tailor its demanded power based upon the desired level of performance. It should be understood that the determination of when to change power contexts may come from a variety of sources. For example, the operating system may determine that a context change is desired (e.g., after a set period of inactivity, by user command, time schedule or the like). In the alternative, hardware may be used to determine when a context change is desired. The context change is accomplished by switching between different sets of Phy interface parameters associated with different power states. For example, a high power state (e.g., higher memory speed) and a low power state (e.g., lower memory speed).
• a high power state e.g., higher memory speed
• a low power state e.g., lower memory speed
• Each power state has an associated set of Phy interface parameters or context (i.e., delay element settings, drive strengths and termination impedances for each signal line). As described in more detail hereafter, switching between power states may be accomplished in several ways. It should be understood that switching between multiple power states as disclosed herein can be applied to any memory type and is not limited to use with DDR memory as used in the examples below.
• the memory controller 18 may access the CSRs
• Address and command (e.g., read, write, do nothing) are sent in the first pipestage, followed by data in the second pipestage as shown in Figure 3. It should be understood that CSRs could be accessed via other communication links.
• the CSR address space is 16 bits wide, allowing for a space of 65,536 unique 16-bit registers. Instead of allowing for such a large space, the address is mapped to allow for the following functions: chiplet identification; intra-chiplet broadcast; compensation broadcast; chiplet instance identification (the D3DBYTE, D3CLK and D3CMP are chiplets that are placed more than once).
• Figure 4 shows a breakdown for CSRs addressing.
• CSRs Only a portion of the CSRs contain values that are relevant to a given power state.
• a set of power context sensitive CSRs are provided for each power state.
• a first set of CSRs are associated with a first power context - PhyPS[0] 44.
• Another set of CSRs are associated with a second power context - PhyPS[l] 46.
• additional sets of CSRs may be provided to support more than two power contexts as shown by PhyPS[n] 48.
• a multiplexer or selection circuitry 50 is provided to select between the different sets of CSRs.
• the Phy interface also contains CSRs that are not power context sensitive. Such CSRs are applicable in all power states.
• PhyPS is shown below in Table 1.
• programming of the relevant fields of the Phy interface is accomplished by issuing commands or programming specific fields in CSRs via the configuration bus 80. For example, changing from one PhyPS to another may be accomplished with a single command issued to the DDR
• the Phy interface may be controlled via a series of commands including: Master_0x08[12] - PhyPS, Master_0x08[8] - PstateToAccess and Master_0xl8[8] - PhyPSMasterChannel.
• the nomenclature [12], [8] and the like refers to the bit position within the command.
• the Master_0x08[12] command corresponds to the current Phy interface P-state (0 or 1). This command controls power context (e.g., which set of CSRs) is currently active.
• the Master_0x08[8] command selects which P- State to read or write to during CSR accesses.
• BIOS may use this method to control which P-State to write to without having to do an actual P-State change. It should be understood that additional bits may be added to support more than two power contexts.
• the Master_0xl8[8] command selects the master channel. In this embodiment, only the channel designated by this bit (master channel) is allowed to issue 0x0B[PhyPS Change] commands. Any 0x0B[PhyPS change] commands issued from other channels will be ignored. It should be understood that additional bits may be added to support more than two channels. In this embodiment, the following OxOB commands are defined:
• the power context is selected via a single bit (i.e.,
• the PhyPSRequest bit (bit position 30) is used to indicate that the command includes a context change.
• SR self refresh
• the Phy interface Upon receipt of the context change command, the Phy interface will change the PhyPS context, the DDR PLL multiplier and divider will be updated, and the PLL will be relocked. When this is all complete, CfgDone will be set. When SR mode is subsequently exited the DLLs will relock. During the time the PhyPS change is occurring the memory controller maintains control over all inputs to the Phy interface (specifically CKE, MemReset, ReadPending, WritePending, all other tri-state controls).
• PhySR may be issued in either channel 0 or 1; making it possible to have one DRAM channel in SR mode while the other is not. In order to fully power down the PClk global grid in the Phy, both channel 0 and 1 need to be in PhySR.
• the OxOB to change PhySR is shown in Table 4 below:
• the OxOB command for the DRAM data rate on the DDR bus is set by BIOS in channel 0 only. Sending OxOB commands to set the DRAM data rate in channel 1 has no effect. It should be understood that other embodiments may support independent DDR data rates on each channel.
• the OxOB DDR rate command is shown in Table 5 below:
• OxOB[DdrRate] command is included for legacy BlOSes.
• BlOSes that understand Phy interface P- States should instead program the DDR Rates for both Phy interface PStates through the direct CSRs Master_OxOO[DdrRate] and Master_0x40[DdrRate]. These rate changes (through the direct CSRs) will only take affect after a subsequent OxOB[PhyPS change].
• 1308878-4 should be understood that embodiments may support multiple high level OxOB commands at once.
• ACPI Configuration and Power Interface
• 15 MRL training may occur here or it may occur later.
• NCLK must be running at the eventual target speed for this DDR rate.
• This DDR rate and other parameters established during this initial training protocol may be used as a first power context (e.g., lower speed - PhyPS[l]). It should be understood that PhyPS[l] may be set based on another DDR rate (i.e., repeat steps 4 through 15 for this frequency).
• the next phase trains for the higher (PhyPS[0]) DDR rate.
• the Write Levelization and RxEn training values are scaled by the MemClk data rate ratio PhyPSO/PhyPSl and used as the seed for the second phase of training in PhyPS[0] . The procedure is initiated as shown in Table 9.
• BIOS may choose which PhyPS context should be used. In order to preserve historical meaning, BIOS may configure the Phy interface for PhyPS [0].
• Resumption from S3 does not involve any DRAM training, only restoring the trained values from nonvolatile state (generally in the South Bridge). Resumption from S3 will typically guarantee (because of ⁇ PwrOk) that the PhyPS context is PhyPSO, Master_0x08[PStateToAccess] is 0, that both channels are out of PhySR, and that the master channel is channel 0 (even if memory is not present on channel 0).
• the procedure for resuming from S3 are generally shown in Table 12:
• the Phy interface is now ready to operate in either PhyPS, and is currently in the
• a warm reset resume is almost identical to a resume from S3.
• BIOS should use a flag (which is reset on cold reset but persistent through warm reset) to indicate whether the training values have been calculated and stored successfully - if during a warm reset, BIOS sees this flag set, it may resume by restoring the trained state.
• the trained state also includes the Master_0xl 8 [PhyPSMaster Channel] as well as any unpopulated channel is left in SR mode. If this flag is not set then BIOS must (re)train the Phy. For purposes of the following disclosure, it is assumed that this flag has been set and that training values have been stored. Therefore warm reset resume does not involve any DRAM training, only restoring the trained values from non-volatile state (generally in the South Bridge).
• Table 13 The procedure for performing a warm reset resume are generally shown in Table 13:
• Table 14 shows a list of all PhyPS CSRs that are duplicated for each power context:
• Examples of computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs).
• ROM read only memory
• RAM random access memory
• register cache memory
• semiconductor memory devices magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs).
• Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine.
• DSP digital signal processor
• ASICs Application Specific Integrated Circuits
• FPGAs Field Programmable Gate Arrays
• Such processors may be manufactured by configuring a manufacturing process using the results of processed hardware description language (HDL) instructions (such instructions capable of being stored on a computer readable media). The results of such processing may be maskworks that are then used in a semiconductor manufacturing process to manufacture a processor which implements aspects of the present invention.
• HDL hardware description language

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