DDR SDRAM – A Second Glance

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Filling In the Gaps

I’ve continued on my quest to get better ‘feel’ for DDR memory, and have been able to do some testing at 266MHz FSB with a Socket A CPU by overriding the multiplier lock. I have now also tested a Socket A Mainboard with the Ali MAGiK 1 DDR chipset, however it is a pre-production part.

First I would like to clarify one item on in my previous article (‘DDR SDRAM – a first glance’). I did run one of the DDR tests listed with PC2100, the Soyo 7VDA Socket 370 (for Intel CPU’s) Mainboard. I had also run it with PC1600 (actually set the memory to HostClk – 33MHz in the BIOS), but did not include any PC1600 results in the article. The difference between PC1600 and PC2100 was so slight I didn’t think it was worth mentioning, but more than one person has asked where the PC1600 tests were… so here are just a few key results from that test:

There is a difference in favor of the PC2100…not much, but it is there. I tested with a 133MHz FSB CPU (PIII 800EB), but I suspect that if I had used a 100MHz FSB CPU and PC1600 vs. 133MHz FSB and PC2100 the difference between the two would have been even greater.

I tend to use a rule of thumb I’ve developed over time: any result within 3% is considered within the margin of error of the test. For the user to detect a performance difference between two systems in actual use there must be a difference of at least 10% between them. In this case we don’t quite even make it to the 3% range, much less 10%.

I’ve also run the Ali MAGiK 1 with a 200MHz FSB, using both PC1600 and PC2100 DDR, and the trend was the same as with the VIA Apollo Pro 266 – very little difference in performance. The VIA Apollo Pro 266 Pentium chipset allows memory to be set at 100MHz or 133MHz when using either a 100 or 133MHz FSB, so I assume the Socket A KT266 will allow for the same. The Ali MAGiK 1 allows (at least on the Soyo K7ADA I tested) the memory to be set for 100 or 133MHz if using a 100MHz HostClk but only 133MHz if using a 133MHz HostClk. The AMD 761 on the other hand appears to only support running the memory at the same speed as the HostClk.

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