These last few pages are like a goldmine of info on using the BIOS with this board. Does anybody know if you need to adjust the Southbridge link speed as well as the Northbridge link speed to adjust the HTT multiplier? The available settings are the same (1000,800,600,400,200).
I ran some experiments with my memory speeds that will be useful for answering some of the above questions. I'm running BIOS v1.20 and 2x1GB Corsair XMS Pro (the ones with the LEDs) at 3,3,3,10.
What I found is that changing the Command Rate from 2T to 1T gives me about a 20% increase in measured memory bandwidth but relatively small gains in real world performance. I also found that I have some strange stability issues at 1T regardless of RAM speed....i.e. I get the same errors with RAM at 180MHz as I do at 250MHz with 1T but completely stable at 2T all the way up to 250MHz.
I also found that setting a memory divider (setting RAM speed at 166MHz in BIOS) with 1T gives me almost identical memory bandwidth as a 1:1 divider (200MHz RAM speed in BIOS) with Command Rate set to 2T regardless of the HTT speed used. Although you get a significant increase in bandwidtch by increasing the speed of the RAM with the command rate unchanged. Running lower latencies (2,3,3,10) gives me a less significant increase in bandwidth.
In all cases I found that overall system performance was far more dependent on CPU speed than on memory bandwidth so it seems clear that setting a memory divider to squeeze a little extra speed from the CPU would be worthwhile in most cases. What you set command rate at will be entirely up to how well your memory performs at given speeds but if you find you can't hold a 1T command rate at high RAM speeds you may find it more beneficial to lower your RAM speed and use 1T than to use 2T in order to push your RAM to it's limits. Running your RAM at lower speeds will of course be less stressful if it is stable at 1T.
Hope this helps.
BTW...running my 3700 San Diego at 2.75GHz is incredible....I'm getting near FX-57 performance out of a 3700. The CPU isn't even breaking a sweat so I'm sure I can go higher now that I understand better how to lower the HTT bus multiplier, and RAM speeds while pushing the CPU higher.
Excellent thread everyone!