PC wont boot unless RAM underclocked?

n111ck

n111ck

n111ck

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I have 4GB of 1066Mhz DDR2 RAM and have just upgraded my E8500 to a Q9650 and now my PC wont boot unless I set the RAM to 667Mhz in the bios?

With the E8500 the RAM could be set to 1066Mhz in the bios and worked fine.

With the Q9650 it would only boot with 2GB at 800Mhz or 4 GB at 667Mhz.

Is there some sort of limit or is there a setting in the bios that I need to adjust to get the full speed from the RAM?

The motherboard is a P5K premium.

:confused:
 
Check that you have set the timings to the advertised defaults when you bought them. Also make sure that the voltage is set to its correct operating levels.
 
Did you reset the BIOS when you installed the new CPU?

You might find the default RAM voltage is too low for 1,066MHz RAM and needs increasing.

Default voltage for DDR2 is usually around 1.8V and 1,066MHz RAM usually need at least 2.0V. You'll have to check the specific voltage for your RAM.
 
Surveyor said:
Did you reset the BIOS when you installed the new CPU?

You might find the default RAM voltage is too low for 1,066MHz RAM and needs increasing.

Default voltage for DDR2 is usually around 1.8V and 1,066MHz RAM usually need at least 2.0V. You'll have to check the specific voltage for your RAM.
Click to expand...

Yes I had to reset the Bios as I had to install a later version.

Does this mean that the CPU is irrelevant to the problem?

Edit:

Ah - changing the voltage to 2.2 lets it boot with the RAM set to 1066MHz - the FSB:DRAM now shows as 5:8 - is this a problem?

Is a 1:1 ratio with slower RAM better than 5:8 with faster RAM?

I'm not interested in oc'ing it etc.
 
Last edited:
The FSB for both processors is 333MHz.

Your RAM needs to run at 533MHz to be at full speed. It doubles to 1,066MHz as it's DDR.

Your memory divider sould be 8:5 (or 5:8 depending which way round you read it) so 333*8/5=533.

The ratio only changes the RAM speed and nothing else so with 1:1 all you are doing is running the RAM at a lower speed and decreasing the performance of your PC.

You need to run at 8:5 or 5:8 (whichever way round it works) so that your memory is reported by CPU-Z (http://www.cpuid.com/softwares/cpu-z.html) at 533MHz.
 
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