Question

COMPUTER ARCHITECTURE

Homework Assignment TOPIC:

Research on various DDR memories:

Write a research paper on the various DDR types that is out there and review the popular clock rate and transfer rates of each

Answer 1

DDR SDRAM :

The second generation of systems running synchronous DRAM use double data rate SDRAM (DDR SDRAM) . DDR SDRAM performs two transfers per clock cycle and features a two bit prefetch buffer. 184 pin DIMM memory modules use DDR SDRAM chips. While DDR SDRAM is sometimes rated in MHz, it is more often rated by throughput (MBps). Common speeds for DDR SDRAM include PC1600(200MHz/1600Mbps), PC2100(266MHz/2100Mbps), PC 2700(333MHz/2700Mbps), PC3200(400MHz/3200Mbps), but other speeds are available from some vendors. The DDR SDRAM gives the transfer rate
(in bytes) of (memory bus clock rate) * 2(for dual rate) * 64 (number of bits transferred) / 8 (number of bits/byte ). Thus DDR SDRAM gives a maximum transfer rate of 1600Mbps

Name	Clock Rate	Transfer rate
DDR-200	100	200
DDR- 266	133*(1/3)	266.67
DDR-333	166*(2/3)	333*(1/3)
DDR-400	200	3200

DDR2 SDRAM :

Double data rate 2 SDRAM is successor to DDR SDRAM . DDR2 SDRAM runs its external data bus at twice the speed of DDR SDRAM and features a four bit prefetch buffer , enabling faster performance. However, it has greater latency than DDR SDRAM memory. Latency is a measure of how long it takes to receive information from memory the higher the number the greater the latency. Typical latency values for mainstream DDR2 memory are CL=5 and CL=6 compared to CL=2.5 and CL=3 for DDR memory. 240 pin modules use DDR2 SDRAM. Its memory might be referred to by the effective memory speed of memory chips on the module. The common speeds for DDR2 SDRAM modules include PC2-3200 (DDR2-400;3200Mbps) , PC2-4200(DDR2-533;4200Mbps) , PC2-5300(DDR2-667;5300Mbps), PC2-6400(DDR2-800;6400Mbps) , PC2-8500(DDR2-1066;8500Mbps).

Name	Clock Rate	Transfer Rate
DDR2-400	100	400
DDR2-533	133*(1/3)	533*(1/3)
DDR2-667	166*(2/3)	666*(2/3)
DDR2-800	200	800
DDR2-1066	266/(2/3)	1066*(2/3)

DDR3 SDRAM:

Compared to DDR2, DDR3 runs at lower voltages has twice the internal banks and most versions run at faster speeds than DDR2, DDR3 also has an eight bit prefetch bus. As with DDR2 versus DDR , DDR3 has greater latency than DDR2. Typical latency values for mainstream DDR3 memory are CL7 or CL9, compared to CL5 or CL6 for DDR2. Although DDR3 modules also use 240 pins their layout and keying are different than DDR2, and they cannot be interchanged. DDR3 SDRAm memory might be referred to by effective memory speed of memory chips on the module. The common speeds for DDR3 SDRAM modules include PC3-6400(DDR3-800), PC3-8500(DDR3-1066), PC3-10600(DDR3-1333), PC3-12800(DDR3-1600), PC3-14900(DDR3-1866), PC3-17000(DDR3-2133).

Name	Clock Rate	Transfer Rate
DDR3-800	100	800
DDR3-1066	133*(1/3)	1066.67
DDR3-1333	166*(2/3)	1333*(1/3)
DDR3-1600	200	1600
DDR3-1866	233*(1/3)	1866*(2/3)
DDR3-2133	266*(2/3)	2133*(1/3)

DDR4 SDRAM :

It stands for Double data rate 4 SDRAM . It is designed to replace the previous standards of DDR. It includes faster data transfer rates and larger capacities , tanks to greater memory density and more memory banks. DDR4 operates at lower voltage.