History of DDR SDRAM

	Revision 4 . . December 6, 2001 2:08 am by Jimbo Wales [Removed copyrighted information]
	Revision 3 . . (edit) December 5, 2001 6:40 pm by Taw [/Talk]
	Revision 2 . . December 5, 2001 6:25 pm by (logged).81.54.xxx
	Revision 1 . . December 5, 2001 6:01 pm by Amin10

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Difference (from prior major revision) (no other diffs)

Changed: 1c1

Rambus memory (RDRAM®) is a revolutionary step from SDRAM. It's a new memory design with changes to the bus structure and how signals are carried. Rambus memory sends less information on the data bus (which is 18 bits wide as opposed to the standard 32 or 64 bits) but it sends data more frequently. It also reads data on both the rising and falling edges of the clock signal, as DDR does. As a result, Rambus memory is able to achieve effective data transfer speeds of 800MHz and higher.

Removed copyrighted text, which appears at:

Changed: 3c3

Another difference with Rambus memory is that all memory slots in the motherboard must be populated. Even if all the memory is contained in a single module, the "unused" sockets must be populated with a PCB, known as a continuity module, to complete the circuit.

http://www.crucial.com/library/ddr_vs_rdram.asp

Changed: 5,12c5

Rambus DRAM modules are known as RIMM™ modules (Rambus inline memory modules). Rambus memory supports both ECC and non-ECC applications. Although the technical realization may be a lot more difficult, the basic principle of DDR-SDRAM is very simple. While the new memory module is clocked at the same speed as normal SDRAM, it is able to transport double the amount of data by using the rising as well as falling edge of the clock signal for data transfers. We are all aware of this technology since AGP2x and JEDEC is already working on the DDR II spec, which will double the data transfer once more, using the quad-pumped technology known from AGP4x or the upcoming Pentium 4 bus. DDR-SDRAM has another important improvement over PC133 SDRAM. Its voltage supply is using only 2.5 V, instead of 3.3 V. This and the lower capacities inside the memory chips lead to a significantly reduced power consumption, which makes DDR-SDRAM also very attractive for notebooks. Unfortunately DDR-SDRAM DIMMs are not compatible with the SDRAM DIMMs we are using now. The new DDR-DIMMs come with 184 instead of the 168 pins used by SDRAM-DIMMs. The module itself looks almost identical to the older SDRAM, but it has only got one notch instead of the two notches found in SDRAM-DIMMs.

It shouldn't be too hard to write a short original article out of that information, though.