Memory FSB : DRAM ratio and G(MCH) question

I believe the G(MCH) is the RAM Multiplier or something, right?
Well in my BIOS, the default G(MCH) is 2.40B, which it says in the details (on the right) is for FSB of 333MHz.

However, when I upped my CPU to 400FSB, I put the thing down to 2.00B as I know 2.40B works, and though B would be the way to go. This also allows my FSB : DRAM to be 1:1, which I thought was pretty neat

However, in the details pane, it also says use 2.00D for an FSB of 400. However, my default FSB is 333, but now it is 400. Does anyone know if I should use 2.00D or 2.00B? Or does it make no difference? I have not tried using D yet as I don't want to break my RAM again

Thanks

Also, I'm not totally sure what G(MCH) is, so any clarification would be lovely too

 

I didn't know any of this either, but hooray for the Internet, I found it!

G(MCH) stands for Graphics and Memory Controller Hub - i.e. the Northbridge. While that title as a BIOS moniker for the memory multiplier doesn't make any sense at all, that's what it is. The number is the multiplier itself [FSB x G(MCH) = RAM freq.], the letter signifies the Northbridge's internal timings - basically latency. D is highest latency, then B, then A, and C is lowest (best) latency. So when the BIOS says that if you have 400FSB and a correct multiplier you should up the letter to D, that means it's increasing latency to compensate for the increase in frequency - exactly the same as you can do on RAM.

My recommendation is to do a stress test with G(MCH) set to 2.00B (tighter latency than 2.00D, and thus theoretically higher performance). If the system makes it through, leave it at 2.00B.


- Diosjenin -

 

Thanks alot, that makes it a fair bit clearer.
Given that it is indeed now running at 400FSB, I'll move the settings along to D and hope performance doesn't down on me. I might be able to tighten the timings then anyway
+rep for you sir