OCZ PC2-4200EB: Reaching for DDR2-800

tRAS and DDR2

OCZ rates the new PC2-4200EB at 3-2-2-8, with 8 a faster tRAS setting than we found in the DDR2 memory roundup. In the roundup we found a tRas setting of 10 was optimum for DDR2 running at 4-4-4 timings. To determine if the OCZ DDR2 ran best at a faster tRAS timing, we first ran Memtest86, a commonly used memory tool that measures memory bandwidth from a custom bootable OS.

Memtest86 showed three distinct tiers of memory bandwidth performance. The range from tRas 2 to tRas 9 showed absolutely no difference in performance. 10 to 12 showed a slight performance drop and 13 to 15, a larger performance drop. Based on Memtest86 performance, a tRAS of 8 seemed reasonable.

OCZ PC2-4200EB - 3-2-2-tRAS
tRAS	Memtest86 Bandwidth
2	3229
3	3229
4	3229
5	3229
6	3229
7	3229
8	3229
9	3229
10	3135
11	3135
12	3135
13	3050
14	3050
15	3050

We have seen reports on the web of claimed fantastic performance using tRAS 2 to 5 settings with this OCZ memory on the Asus P5AD2-E. This is the same board used in our new DDR2 memory test bed. So as a further check, performance tests were run varying tRAS from 2 to 15 using Everest (formerly Aida32). With Everest read/write/composite, performance was measured with 3-2-2- timings and a variable tRAS. Performance patterns in Everest were exactly the same as in Memtest86, with extremely small variations from 2 to 9 tRAS. An example is the tRAS 2 composite of 5663 compared to the tRAS 8 composite of 5686.

Our conclusion is tRAS from 2 to 9 makes no performance difference with the OCZ PC2-4200EB, so we ran all performance tests at 8. If you see enthusiasts claiming improved DDR2 performance with tRAS 2 to 5, ask for proof - as we can find no real performance difference in the 2 to 9 range with all other settings being the same.