Quote Originally Posted by gtj View Post
I may have been one of those who said 1:1 is the best but after doing the math and running benchmarks, I've changed my mind and may have to apologize for making statements without evidence to back them up.

1:1 sounds nice. The FSB and memory are running at the same clock speeds so that must be the most efficient, right? All other things being equal, maybe 1:1 is more efficient that 4:5 but the reality is somewhat different.

The fact is that any "efficiency" the MCH may see is vastly overwhelmed by another fact.... Data passing between the processor and memory is limited by the SLOWEST link. If your FSB is running at 8 GB/s and your memory bus is running at 6 GB/s, then data can only pass between the processor and memory at 6 GB/s. PERIOD. If moving your ratio from 1:1 to 4:5 brings the memory bus to 7 GB/s that's a 17% increase. Gee, so it may not be as efficient as 1:1. Who Cares? Honestly, I can't even find any documentation to support that there was any efficiency loss in the first place.

This is easy to test. Set your FSB to a value that let's you run 1:1 plus either 2/3 or 4/5 reliably. Run an Everest Cache and Mmeory benchmark at 1:1, then without changing anything else, set a 2/3 or 4/5 and run the benchmarks again. Throughput should go up and latency should go down. What a concept.
Setting say FSB to 400... Then running 266ref and mem at 533 gives you DDR2 800 1:1 but if you set 667 it gives you ddr2 1000 4:5 and if you keep the same timings and FSB of course its going to be faster and have lower latency you changed the memory frequency to 500 instead of 400. Or am I reading what you said wrong?