Bandwidth efficiency dropping >= 166fsb on 8K5A2?

Hello guys. Having a bit of a problem here. While testing in sisoft I notice with full tweaks the bandwidth efficiency from 100-165fsb stays around 94 percent. This of course means if the maximum bandwidth of the bus (at 133.33mhz fsb, 266.66DDR) is 2.1gb/s then 2.1*0.94 = 1.974gb/s actual throughput.

Now, this is my problem. After going up to and greater than 166fsb the efficiency stays around 84%. Doesn't matter what timings I set in the bios (normal, turbo, etc) it's always 84%. Any ideas as to whats causing this?

Using:
Epox 8K5A2 (with I believe is the latest bios, not sure)
two Corsair PC2400XMS 256mb dimms in the furthest slots from the CPU.

Any help would be appreciated.

The maximum bandwidth of your memory bus depends on your setting. The 2.1 GB/s max you quoted is correct for stock specs. Now when your begin to run your mem bus at 165 for instance, your max throughput will now be 2,640 MB/s. If your efficiency is 94%, then you should have an actual throughput of 2,481 MB/s. The efficiency usually doesn't change drastically as your increase/decrease bus speed as long as mem is 1:1 with FSB.
Re run the Memory Bench again. Make sure you pay attention to which break down your looking at. There are two:
1) Integer
2) Float
Run the bench at 165 and 166, all timings at turbo. Record data for both break downs at each the 165 and 166 MHz turbo settings. Above all make sure the MEMORY IS IN SYNC WITH THE FSB. Post the results back.

-PC

Aaron Gordon said:

Hello guys. Having a bit of a problem here. While testing in sisoft I notice with full tweaks the bandwidth efficiency from 100-165fsb stays around 94 percent. This of course means if the maximum bandwidth of the bus (at 133.33mhz fsb, 266.66DDR) is 2.1gb/s then 2.1*0.94 = 1.974gb/s actual throughput.

Now, this is my problem. After going up to and greater than 166fsb the efficiency stays around 84%. Doesn't matter what timings I set in the bios (normal, turbo, etc) it's always 84%. Any ideas as to whats causing this?

Using:
Epox 8K5A2 (with I believe is the latest bios, not sure)
two Corsair PC2400XMS 256mb dimms in the furthest slots from the CPU.

Any help would be appreciated.

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