1. The Evolution of Dynamic Random Access Memory (DRAM) CS 350 Computer Organization and Architecture Spring 2002 Section 1 Nicole Chung Brian C. Hoffman Joel D. Throckmorton Thomas C. Wear

2. DRAM Manufacturer: IBM Speed: 35-200ns Year Introduced: 1969 Frequency: 4.77- 40MHz Burst Timing: 5-5-5-5 Pins: SOJ(20,24,26) Voltage: +5v,-5v,+12v

3. Similar to manufacturing processors Multiplexed address lines Separate data inputs and outputs Three control signals Two primary effects DRAM

4. FPM DRAM Manufacturer: many Speed: 50ns Year Introduced: 1987 Frequency: 16-66 MHz Burst Timing: 5-3-3-3 Pins: 72/168 Voltage: 5.0v Bandwidth: 188.71MBs

5. Simple DRAM slightly slower than FPM How it works “Safe” Used primarily for main system memories Not well-suited for high-performance video applications FPM DRAM

6. EDODRAM Extended Data Output Random Access Memory Introduced in 1994, Improvement over FPM Up to 40% increase in access time, over FPM EDO shortens the read cycle between the memory and the CPU EDO chips still hold data valid after the signal that “strobes” the column address goes inactive. Meaning, the CPU can perform other operations while memory is being accessed.

7. EDODRAM EDODRAM runs asynchronously w/ the CPU clock SDRAM has taken the place of EDODRAM There is no difference between SDRAM and EDO at bus speeds at or below 83MHz. EDO timing: 5-2-2-2 at 66 MHz

8. BEDODRAM Burst EDODRAM Introduced in 1995 Read/write cycles were batched in bursts of four “ The memory bursts wrap around on a four byte boundary which means that only the two least significant bits of the CAS (Column Address Strobe) are modified internally to produce each address of the burst sequence” BEDO memory speed ranged from 40-66 MHz which was faster than the FPM at 33MHz

9. BEDODRAM At bus speeds at or below 100 MHz, BEDO would have been faster and more reliable than SDRAM BEDO never really took off There was more support for the production and development of SDRAM

10. SDRAM differs from past DRAM in two ways The way it’s organized –Multiple banks on a single DIMM –Allows banks to recharge while others read/write The way it’s controlled –Synchronous (aligned with the clock) –Performs commands that are fed by the clock signals

11. SDRAM Ratings PC66, PC100, PC133 –SDRAM ratings which describe which bus speeds the RAM will support and work correctly with. –Ratings can also be in form x-y-z: CAS latency (X) RAS-to-CAS delay (Y) RAS precharge time (Z) –There is tolerance (83MHz,100MHz works in 66MHz bus)

12. RDRAM (Rambus) Single chip Low pin count High capacity High bandwidth

14. Rambus Channel Diagram

15. Double Data Rate SDRAM Introduced in 2000 - Doubles bandwidth by accessing data on both the “rising edge” and “falling edge” of the memory bus clock - 2.5V versus 3.3V of the PC133 SDRAM 184-pin DDR DIMMs versus 168-pin SDRAM DIMMs

16. DDR SDRAM Politics ISSUE 1 – Support –AGP standard (NVIDIA GeForce 3D) –Intel exclusive deal with Rambus –AMD and VIA support DDR SDRAM

17. DDR SDRAM Manufacturers Hitachi Hyundai IBM Infineon Micron Mitsubishi Toshiba NEC

18. DDR SDRAM Politics Issue 2 – Name –Proposed: DDR SDRAM PC200/266 –(100/233 MHz memory bus) –Conflict: Rambus RDRAM PC600/700/800

19. DDR SDRAM Politics Issue 2 – Name (cont.) –DDR SDRAM Resolve… use the peak data transfer rate… PC1600 = PC200 Formula (64 bit * 2 * 100MHz = 1600 MB/sec) PC2100 = PC233 Formula (64 bit * 2 * 133MHz = 2133 MB/sec

20. Citations Arnold, Eric (2002). “Computer Memory Ram Sdram Buffered Pc66 Pc100 Pc133 Mem Dram.” URL: http://home.cfl.rr.com/bjp/ Cullen, Drew (2002). “Hynix Rations DDR Supply.” URL: http://www.theregister.co.uk/content/3/23876.html Howe, Denis (1996). “Dynamic Random Access Memory by FOLDOC.” URL: http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?DRAM Howe, Denis (1996). “Page-Mode Dynamic Random Access Memory.” URL: http://burks.brighton.ac.uk/burks/foldoc/94/85.htm Kanellos, Michael (2002). “Memory Market Optimistic about 20002.” URL: http://zdnet.com.com/2100-1103-858175.html Kozierok, Charles (2001). “PC-Guide Ref DRAM Technologies.” URL: http://www.pcguide.com/ref/ram/tech_FPM.htm

21. Citations Kozierok, Charles (2001). “PC-Guide Ref DRAM Technologies.” URL: http://www.pcguide.com/ref/ram/techDDRSDRAM-c.html Micron Technology(2000) “Memory Upgrades.” URL: http://www.crucial.com/DDR/index.asp Pabst, Thomas (2002). Tom’s Hardware Guide, “RAM Guide.” URL: http://www6.tomshardware.com/mainboard/98q4/981024/ Russell, Rick (2000). “The Memory Conundrum.” URL: http://peripherals.about.com/library/weekly/aa021300a.htm?terms =DDR+DRAM Thing, Lowell (2001). “What is.” URL: http://whatis.techtarget.com/definition/0,,sid9_gci213955,00.html