Embodiments of the invention relate to memory systems and methods for controlling memory devices.
Processor-based systems use memory devices, such as dynamic random access memory (“DRAM”) devices, to store data (e.g. representing instructions, data to be processed, etc.) that are accessed by the processor. In a typical computer system, the processor communicates with the system memory including the memory devices through a processor bus and one or more memory controllers. In some memory systems, a group of memory devices of the system memory are controlled by an associated memory controller. The processor issues to the memory controller a memory request including a memory command, such as a read command, and an address designating the location from which data are to be read from memory. The memory controller uses the command and address to generate appropriate memory commands as well as row and column addresses, which are applied to the memory devices associated with that memory controller. In response to the commands and addresses, data is transferred between the memory devices and the processor.
Memory devices require a certain amount of time to service a memory request due to the time necessary to access the appropriate rows and columns of the memory device and actually retrieve the requested data. Further time is required to drive read data and read commands onto and off of a common interface between the memory devices and the controller. Although the operating speed of memory devices is continually increasing, the increase in device speed has not kept pace with increases in the operating speed of processors. The operation of the memory device itself therefore often limits the bandwidth of communication between the processor and the system memory.
To improve overall memory access bandwidth, one memory controller typically controls access to more than one memory device. In some systems, the processor interfaces with several memory controllers, each of which in turn control access to several memory devices. In this manner, further memory commands may be issued by a processor or memory controller while waiting for a memory device to respond to an earlier command, and bandwidth is improved. When a memory controller shares a common interface with multiple memory devices however, timing problems may occur. Commands and addresses sent from the memory controller, which are represented by electrical signals coupled to conductive signal lines of the interface, may reach different memory devices at different times, depending on the layout of the memory system. Furthermore, different memory devices may take different amounts of time to respond to memory commands depending on the process variations that occurred during fabrication of the memory devices. Variations in temperature may also cause variation in response time between memory devices.
Accordingly, there is a danger of a conflict on the common interface between multiple memory devices and a memory controller. For example, one memory device may attempt to place read data on the interface at the same time as data from another memory device is being carried by the interface. Such a data collision would result in a loss of usable data and is unacceptable. This problem can be alleviated by providing a common clock signal to each memory device that is synchronized to a system clock signal used by the memory controller. Each memory device may then decide when to place data on the interface by counting received clock periods. By referencing a common clock signal the memory device can ensure it places data onto the bus during a clock cycle designated for its use. When the memory device places data onto the interface, it then also sends a data strobe signal for use by the controller in identifying and synchronizing received read data. The use of common clock signals for synchronizing operation of the memory devices and strobe signals may require additional circuitry and further pins on the memory device.
However, the transmission of clock signals for each memory device may increase complexity of the system and consumes space and power at the memory device. Further, it may be desirable to decrease the number of output pins on the memory device. What is needed is a system that avoids data collisions on a common interface but does not rely on the use of a common clock signal at the memory device.
Embodiments of the present invention are directed toward memory systems and methods for controlling memory devices. Certain details are set forth below to provide a sufficient understanding of embodiments of the invention. However, it will be clear to one skilled in the art that embodiments of the invention may be practiced without various of these particular details. In some instances, well-known circuits, control signals, timing protocols, and software operations have not been shown in detail in order to avoid unnecessarily obscuring the described embodiments of the invention.
A system 100 according to an embodiment of the present invention is shown in
The controller 115 is configured to transmit commands, addresses and data, which are represented as electrical signals, and control signals to the memory devices over the interface 110. In some embodiments, however, only data signals are transmitted on the shared interface 110 and command or address signals, or both may be transmitted over another interface. The controller transmits a variety of commands to ensure proper operation of the memory devices. The controller determines when to transmit commands using a controller clock signal.
A read operation will now be described to generally illustrate operation of the system 100. The controller 115 transmits a read command onto the interface 110. Read commands for the memory device 105 (shown in
Data may be read from the array 130 in a burst manner. After specifying an initial address, data from several memory cells in the array 130 may be read sequentially. A larger amount of data may be read from the array 130 than can be placed on the interface 110 at one time. In such a case, the read data is serialized for transmission on the interface 110. For example, as indicated in
As will be described in more detail below, the functional blocks shown in
As described above with reference to
In an example of a conventional timing protocol implemented by the system of
Read data is output by the memory in a certain unit time interval. A unit time interval corresponds to a single data transmission. The example in
The next read command 230 is directed to a different memory device, DRAM1. If the read command were directed to the same memory device as the read command 210, the controller could transmit the command immediately following the initial read command 210, at time T1. However, because the read command 230 is directed to a different memory device (i.e., DRAM1), the controller delays transmission of the read command 230 by one controller clock period, shown as the “no operation” (NOP) command 235 in
The method described with reference to
One or more embodiments of the present invention reduce the bandwidth penalty associated with the operation of the system 100. It may not be necessary to insert a full controller clock period in between consecutive reads to different memory devices. The variation in travel time for signals to different devices and the variation in access time for the devices may be such that one unit time interval of time delay is sufficient. Accordingly, some embodiments of the invention delay the retrieval of available read data from a memory device by one unit time interval when consecutive read commands are issued to different devices. An example of a timing diagram illustrating such an embodiment is shown in
The next read command 320 is also transmitted to a different memory device than the previous read command 230. In
Each consecutive read command 210, 230, 320, 335, and 340 in
As shown in
The buffer memory 140 may include a read and a write pointer to indicate where data can be written and where data can be read. The vStrobe signal causes data to be transmitted from the output register 135 to the interface 110, as described above. The vStrobe signal may also cause the read pointer of the buffer memory 140 to increment, passing the next stored data to the output register 135. The memory array 130 may transmit a data strobe signal to the buffer memory 140 when read data is available, incrementing the write pointer such that the retrieved data is written to correct locations. In summary, operation of an embodiment of the invention as discussed above with reference to
Another embodiment of the present invention may reduce the required memory in the buffer memory 140. Recall the buffer memory 140 has sufficient memory to store read data that may be obtained from the array 130 during a period the vStrobe signal is delayed, which may be as much as three unit time intervals in one embodiment. To reduce the size of the buffer memory 140, or in some embodiments, eliminate a need for the buffer memory 140, timing of the transmission of read commands may be varied instead of the timing of the strobe signal, as shown in
In this manner, read commands are transmitted by the controller either four unit time intervals or six unit time intervals apart. A subsequent read command may be transmitted four unit time intervals following the transmission of a previous read command when reading from a same memory device, and six unit time intervals following issuance of a previous read command when reading from a different memory device. The vArrayCyc signal is changed to transmit pulses both four and six unit time intervals after an transmitted read command, as shown in
As discussed above with reference to
A delay control signal 500 is provided to the delay circuit 150 to indicate whether the delay circuit 150 should be used to delay the command signal. When the delay control signal 500 is low, the read command 210 will be captured by the DRAM0 on a rising edge of the vArrayCyc signal 220, at a time shortly after T0 in
When a read command is again transmitted to a different memory device, the command itself may be delayed by two unit time intervals, as shown by read command 320 in
An embodiment of a processor-based system 700 according to the present invention is shown in
The controller 115 may be part of a larger logic die 630 that may communicate with a processor 705 through a relatively narrow high-speed bus 706 that may be divided into downstream lanes and separate upstream lanes (not shown in
The DRAM devices 105, 600, 605 and 610 are connected to each other and to the logic die 630 by a relatively wide interface 110. The interface 110 may be implemented using through silicon vias (“TSVs”), as described above, which allow for formation of a large number of conductors extending through the DRAM devices 105, 600, 605, 610 at the same locations and connect to respective conductors formed on the devices 105, 600, 605, 610 to form vertical interfaces. In one embodiment, each of the DRAM devices 405, 600, 605, 610 are divided into 16 autonomous partitions, each of which may contain 2 or 4 independent memory banks. In such case, the partitions of each device 105, 600, 605, 610 that are stacked on top each other may be independently accessed for read and write operations. Each set of 16 stacked partitions may be referred to as a “vault.” Thus, memory device 105 may contain 16 vaults. In one embodiment, the controller 115 is coupled to one vault through the interface 110 and a separate controller is provided for other vaults in the devices 105, 600, 605, 610.
The computer system 700 includes a processor 705 for performing various computing functions, such as executing specific software to perform specific calculations or tasks. The processor 705 may be coupled to input devices 710, or output devices 715, or both. In some cases, a device may perform both an input and output function. Any type of input and output devices may be used such as storage media, keyboards, printers and displays. The processor generally communicates with the controller 115 over a processor bus 706, and may communicate address, command, and data signals. The controller then communicates with the memory devices over a further interface, as discussed above.
From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention.
This application is a continuation of U.S. patent application Ser. No. 12/128,883, filed May 29, 2008, and issued as U.S. Pat. No. 8,521,979 on Aug. 27. 2013. This application and patent are incorporated herein by reference, in their entirety, for any purpose.
Number | Name | Date | Kind |
---|---|---|---|
5179303 | Searles et al. | Jan 1993 | A |
5263032 | Porter et al. | Nov 1993 | A |
5748914 | Barth et al. | May 1998 | A |
5774475 | Qureshi | Jun 1998 | A |
5960008 | Osawa et al. | Sep 1999 | A |
5982684 | Schwartzlow et al. | Nov 1999 | A |
6052329 | Nishino et al. | Apr 2000 | A |
6122688 | Barth et al. | Sep 2000 | A |
6177807 | Bertin et al. | Jan 2001 | B1 |
6181616 | Byrd | Jan 2001 | B1 |
6247138 | Tamura et al. | Jun 2001 | B1 |
6285211 | Sample | Sep 2001 | B1 |
6363017 | Polney | Mar 2002 | B2 |
6401213 | Jeddeloh | Jun 2002 | B1 |
6519194 | Tsujino et al. | Feb 2003 | B2 |
6574626 | Regelman et al. | Jun 2003 | B1 |
6650157 | Amick et al. | Nov 2003 | B2 |
6658523 | Janzen et al. | Dec 2003 | B2 |
6839260 | Ishii | Jan 2005 | B2 |
6882304 | Winter et al. | Apr 2005 | B2 |
6889334 | Magro et al. | May 2005 | B1 |
6907555 | Nomura et al. | Jun 2005 | B1 |
7058865 | Mori et al. | Jun 2006 | B2 |
7107424 | Avakian et al. | Sep 2006 | B1 |
7135905 | Teo et al. | Nov 2006 | B2 |
7149134 | Streif et al. | Dec 2006 | B2 |
7168005 | Adams et al. | Jan 2007 | B2 |
7171596 | Boehler | Jan 2007 | B2 |
7184916 | Resnick et al. | Feb 2007 | B2 |
7197101 | Glenn et al. | Mar 2007 | B2 |
7203259 | Glenn et al. | Apr 2007 | B2 |
7243469 | Miller et al. | Jul 2007 | B2 |
7389375 | Gower et al. | Jun 2008 | B2 |
7464241 | Pete | Dec 2008 | B2 |
7466179 | Huang et al. | Dec 2008 | B2 |
7489743 | Koh et al. | Feb 2009 | B2 |
7567476 | Ishikawa | Jul 2009 | B2 |
7697369 | Koshizuka | Apr 2010 | B2 |
7710144 | Dreps et al. | May 2010 | B2 |
7764564 | Saito et al. | Jul 2010 | B2 |
7772907 | Kim et al. | Aug 2010 | B2 |
7855931 | LaBerge et al. | Dec 2010 | B2 |
7979757 | Jeddeloh | Jul 2011 | B2 |
8010866 | LaBerge | Aug 2011 | B2 |
8127204 | Hargan | Feb 2012 | B2 |
8248138 | Liu | Aug 2012 | B2 |
8289760 | Jeddeloh | Oct 2012 | B2 |
8356138 | Kulkarni et al. | Jan 2013 | B1 |
8400808 | King | Mar 2013 | B2 |
20020004893 | Chang | Jan 2002 | A1 |
20020054516 | Taruishi et al. | May 2002 | A1 |
20020097613 | Raynham | Jul 2002 | A1 |
20020125933 | Tamura et al. | Sep 2002 | A1 |
20020130687 | Duesman | Sep 2002 | A1 |
20020133666 | Janzen et al. | Sep 2002 | A1 |
20020138688 | Hsu et al. | Sep 2002 | A1 |
20030041299 | Kanazawa et al. | Feb 2003 | A1 |
20030132790 | Amick et al. | Jul 2003 | A1 |
20040073767 | Johnson et al. | Apr 2004 | A1 |
20040098545 | Pline et al. | May 2004 | A1 |
20040160833 | Suzuki | Aug 2004 | A1 |
20040168101 | Kubo | Aug 2004 | A1 |
20040199840 | Takeoka et al. | Oct 2004 | A1 |
20040206982 | Lee et al. | Oct 2004 | A1 |
20040237023 | Takahashi et al. | Nov 2004 | A1 |
20040246026 | Wang et al. | Dec 2004 | A1 |
20050005230 | Koga et al. | Jan 2005 | A1 |
20050071707 | Hampel | Mar 2005 | A1 |
20050091471 | Conner et al. | Apr 2005 | A1 |
20050144546 | Igeta et al. | Jun 2005 | A1 |
20050157560 | Hosono et al. | Jul 2005 | A1 |
20050174877 | Cho et al. | Aug 2005 | A1 |
20050278490 | Murayama | Dec 2005 | A1 |
20050289435 | Mulla et al. | Dec 2005 | A1 |
20060036827 | Dell et al. | Feb 2006 | A1 |
20060059406 | Micheloni et al. | Mar 2006 | A1 |
20060123320 | Vogt | Jun 2006 | A1 |
20060126369 | Raghuram | Jun 2006 | A1 |
20060223012 | Sekiguchi et al. | Oct 2006 | A1 |
20060233012 | Sekiguchi et al. | Oct 2006 | A1 |
20060245291 | Sakaitani | Nov 2006 | A1 |
20060253723 | Wu et al. | Nov 2006 | A1 |
20060262587 | Matsui et al. | Nov 2006 | A1 |
20060273455 | Williams et al. | Dec 2006 | A1 |
20070058410 | Rajan | Mar 2007 | A1 |
20070070669 | Tsern | Mar 2007 | A1 |
20070074093 | Lasser | Mar 2007 | A1 |
20070136645 | Hsueh et al. | Jun 2007 | A1 |
20070271424 | Lee et al. | Nov 2007 | A1 |
20080147897 | Talbot | Jun 2008 | A1 |
20080150088 | Reed et al. | Jun 2008 | A1 |
20080250292 | Djordjevic | Oct 2008 | A1 |
20090006775 | Bartley et al. | Jan 2009 | A1 |
20090016130 | Menke et al. | Jan 2009 | A1 |
20090021992 | Oh | Jan 2009 | A1 |
20090091966 | Dietrich et al. | Apr 2009 | A1 |
20090196093 | Happ et al. | Aug 2009 | A1 |
20090251189 | Hsieh | Oct 2009 | A1 |
20090300314 | Laberge et al. | Dec 2009 | A1 |
20090300444 | Jeddeloh | Dec 2009 | A1 |
20100005217 | Jeddeloh | Jan 2010 | A1 |
20100005376 | Laberge et al. | Jan 2010 | A1 |
20100014364 | Laberge et al. | Jan 2010 | A1 |
20100031129 | Hargan | Feb 2010 | A1 |
20100042889 | Hargan | Feb 2010 | A1 |
20100070696 | Blankenship | Mar 2010 | A1 |
20100079180 | Kim et al. | Apr 2010 | A1 |
20100091537 | Best et al. | Apr 2010 | A1 |
20100110748 | Best | May 2010 | A1 |
20110075497 | Laberge et al. | Mar 2011 | A1 |
20110271158 | Jeddeloh | Nov 2011 | A1 |
20110296227 | LaBerge et al. | Dec 2011 | A1 |
20120144276 | Hargan | Jun 2012 | A1 |
20120155142 | King | Jun 2012 | A1 |
20130208549 | King | Aug 2013 | A1 |
20130346722 | LaBerge et al. | Dec 2013 | A1 |
20140053040 | Hargan | Feb 2014 | A1 |
Number | Date | Country |
---|---|---|
101036131 | Sep 2007 | CN |
05-265872 | Oct 1993 | JP |
0774620 | Mar 1995 | JP |
11-102599 | Apr 1999 | JP |
11-513830 | Nov 1999 | JP |
2003-303139 | Oct 2003 | JP |
2004-327474 | Nov 2004 | JP |
2005-4947 | Jan 2005 | JP |
2007-507794 | Mar 2007 | JP |
2007-140948 | Jun 2007 | JP |
2007-226876 | Sep 2007 | JP |
2007-328636 | Dec 2007 | JP |
2008-112503 | May 2008 | JP |
2008-140220 | Jun 2008 | JP |
2010-514080 | Apr 2010 | JP |
WO-9714289 | Apr 1997 | WO |
WO-2005033958 | Apr 2005 | WO |
WO-2007038225 | Apr 2007 | WO |
WO-2007095080 | Aug 2007 | WO |
WO-2008054696 | May 2008 | WO |
WO-2008076790 | Jun 2008 | WO |
WO-2009148863 | Dec 2009 | WO |
WO-2010002561 | Jan 2010 | WO |
WO-2010011503 | Jan 2010 | WO |
WO-2012060097 | May 2012 | WO |
WO-2012082338 | Jun 2012 | WO |
Entry |
---|
Taiwanese Search Report for Application No. TW 098114848, dated Mar. 11, 2013. |
International Search Report and Written Opinion dated Jan. 6, 2010 for International Application No. PCT/US2009/045059. |
Office Action for TW 098114848 dated Mar. 11, 2013. |
Number | Date | Country | |
---|---|---|---|
20130318298 A1 | Nov 2013 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 12128883 | May 2008 | US |
Child | 13956045 | US |