Crucial PC3200 Memory Review - Overclocking
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While Crucial makes it clear that it does not support overclocking, that's not likely to stop a few people from doing it, especially me. It is important to keep in mind that this RAM is not designed to overclock, so I didn't have extremely high expectations for this RAM. Two things I want to have explained are latencies and dividers, so I'll refer to DMOS' memory article again:
"Latency is defined as the time differential between when a command is given, and when that command is actually executed. In any memory read/write operation, there are many factors that add to the latency. One of the first happens when the Front Side Bus and memory controller are not running at the same clock speeds. When using any divider other than 1:1, the two devices have to wait for the clocks to match up before any signal can be sent between the two. For example, when a memory divider of 5:4 is chosen, for every 5 cycles of the FSB, the memory will only complete 4. That means that only every 5 cycles of the FSB can they actually talk to each other. So if a command is sent from the CPU to the memory requesting a read of data on the second cycle after they just matched, the request must sit there waiting 3 more cycles before that request can actually go out. This is why it is always better for memory performance to try and use a 1:1 divider over all others, and hence the proliferation of high speed modules in today's market, to match up with the faster and faster FSB's being used."
In essence, a divider is the ratio of the speeds between the front side bus (FSB) and the memory controller. A computer running a 5:4 divider with a FSB at 250 MHz really runs its memory at 200 MHz. Latencies and dividers go hand in hand.
I began to overclock the memory by raising the FSB in increments of 5 MHz, leaving the memory at 200 MHz and using a 1:1 divider. Timings were left at SPD. I was able to get the FSB to 230 MHz before memtest86 started detecting failures. Running 3DMark 2001SE at this speed I was able to get a score of 13080, and SANDRA said that the memory bandwidth was 4814 MB/s for integer and 4822 MB/s for floating point.
Dropping the memory to a 5:4 divider, I tried to see how far I could go. I continued with the 5 MHz FSB increase until I hit 250 MHz, because at 255 MHz, memtest86 was showing a lot of failures. Adding voltage didn't help. I gave up here, and got scores of 13284 on 3DMark 2001SE as well as 4988 MB/s and 5000 MB/s on SANDRA's integer and floating point memory bandwidth tests respectively.
As you can see, there are lots of performance gains to be had by overclocking.
Next: Conclusion >>
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