a_ross84

This might have already been posted. Sorry if it has, Im new here.

I have an ASUS P5N32-e SLI plus motherboard with a Pentium D 3 ghz Processor. I have recently upgraded my ram and for some reason the new RAM wqont run at full speed. The RAM is OCZ 4gb DDR2 800Mhz but is only running at 400 Mhz. can anyone help at all?

manic

The speed can be confusing. Ram configs are confusing anyway.
But here is my take on your situation. 400mhz x 2 =800mhz fsb.
ddr2 multiply x 2. Ive never seen a post, that says your running at
800mhz fsb, just 400mhz, in dual mode, or single mode. Thats how I
figure it anyhow. Im sure someone will explain it better, or even correct
my sketchy answer.

Stu_computer

hi ross, welcome to tsf.

basically what is happenig when you set the front side bus (fsb) to 400MHz is a train of 400,000,000 pulses is generated every second, so it might look like this...
__┌--┐__┌--┐__┌--┐__┌--┐__(example of 4 pulses).

each pulse has a leading edge that rises (0v -> 5volts)
and a trailing edge that drops (5v -> 0volts)

leading edge _┌ pulse (5volts)-┐_ trailing edge ___ 0 volts

with DDR1 RAM only the leading edge of a pulse is used for timing--hence it runs at 400MHz because it sees 400,000,000 timing signals.

with DDR2 RAM both the leading edge and the trailing edge of each pulse is used for timing--hence it runs at 800MHz because it sees 800,000,000 timing signals.

simply, if only one edge of a pulse is the trigger then the RAM speed is the same as the FSB speed, but by using both edges of a pulse the triggering happens twice for every pulse and RAM speed is doubled.

a_ross84

Thanks for the reply guys. Would you be able to tell me how to change it to run at 800Mhz? I was running DDR1 up untill i fitted this new RAM. im just unsure as to how i go about speeding it up.