*NOTE* This has originated from www.extremeoverclocking.com and their forums. I take no credit in the making of this guide as I am not the aurthor. I am simply reposting this for others to view.
Here's a handy guide I wrote with an enclosed tool to help calculate different ram speeds and cpu clock speeds using different memory dividers and multi's. Big thanks to goddh0r for writing A64 MemFreq 1.1 Program!
A ram divider is usually a setting found in your ram tweaking setting menu in your bios. dividers usually are 200(1:1), 166, 150, 133, 100 or 400, 333, 266, 200. etc..
The lower you go on the divider, the less ram speed is used. The whole point of a divider is if your memory can't keep up with your fsb. say you have an a64 3200+ that does 2.5 ghz. you would normally do 250x10 ram 1:1 (ram 250 also) 1:1 HTT=ram speed 250=250.
but in your case you have ram that won't do 250mhz, so you need to use a divider. Download this zip file and type the HTT(fsb) in the top line and go from there. This will help you find your sweet spot. You can use it to help calculate your ram speed and total cpu clock by using different dividers and cpu muti's. AMD64 multi's are unlocked downwards. so if you have default multi of 10, then you can use 9, 8, 7, 6, 5, don't go below 5. In the case of an FX, the multi is unlocked both ways.
Just think of your cpu max clock and your ram's max clock and find the best way to utilize the most from each.
ex. Joe has an athlon 64 that does 2.53 ghz. stable. but his bh6 ram only goes up to 232mhz at 2-2-2-6 1T. what does Joe do? he does this: set's the cpu multi at 9. sets ram divider at 166. sets his HTT(fsb) at 280. bingo! Joe's cpu is now doing 2.52ghz(9*200) and his ram is doing 229mhz!
Here's another example: Steve just shelled out $250 on some new TCCD that does 284mhz at 2.5-3-3-7 1T. He has a crappy 3500+ that only does 2.58 ghz. Steve assumes that because his cpu only does 258x10, his ram will have to run at 258 too. But Steve wants to use all that bandwidth of his tccd, but doesn't want to go over his cpu speed. So what does Steve do?
Steve set's his multi to 9 and runs his ram up to 284 1:1. Now his cpu is at 2.55(9x284) and his ram is ripping at 284mhz like it should! Steve is very happy and he is glad he spent the money on his new ram.
GENERAL RULES ON A64:
Remember, never use .5 multis.
never use multi under 5.
For best performance use 1T command setting(I've found 2T command is about the equivalent to a 20mhz loss in memory performance)
IMPORTANT!!!
Depending on your A64 chipset your total HTT(fsb) and HT multi(2x, 3x, 4x, etc.) should never exceed the total hyper transport link speed. ex. NF3 250 ultra has max of 1000mhz hyper transport link. So if fsb is 290 and htt is at 5x(200*5=1000) 5x290=1450 BAD!!!
to fix. just lower the HT multi(hyper transport Link) to 3x(200*3=600) so 3*290=870 total hyper transport speed. GOOD! you kept it under 1000!