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Different memory/CPU ratios in BIOS and CPU-Z

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June 2, 2009 6:28:08 AM

Hi guys,

I've been reading a lot these days about my problem but couldn't find something that would apply to my situation.

OK so I'm trying to overclock my girlfirend's old Sempron 2600+ 1.6 Ghz on her old Asus K8V-X SE motherboard, 512 MB RAM DDR400 Kingston.

Default settings: 8x multiplier (locked), FSB 200, memory:CPU ratio - 1:1.
In CPU-Z, Memory tab, I get 200Mhz, that would be 2x200 = 400.
OK, no problem there.

In BIOS I set the FSB to 266, the memory:CPU ratio to 4:3 and also the AGP/PCI to 66/33.
So now I should get 266*8=2128 Ghz to the CPU and 3/4=0,75*266=199,5x2=399 Mhz to the RAM, right? Also the AGP/PCI slots should be OK.

I boot into Windows, open CPU-Z and in the Memory tab I get 177,3 Mhz instead of 199,5 and a ratio of CPU/12 -> 2128/12=177,33333?!?!

I restart the computer, go into BIOS again, set the memory:CPU ratio to 3:2 just to see what happens, I lower the FSB to 250 and load Windows again.
Now CPU-Z reads 2000 Ghz to the CPU (250*8) and 200 Mhz to the memory, with a ratio of CPU/10, when in fact the memory reading should be at 2/3=0,66*250=166,66 Mhz?!

As far as I see it, the BIOS calculation should be right. Do I just have to ignore the CPU-Z results regarding memory speeds and stick to the first setting or am I missing something?
a b à CPUs
a b } Memory
a b K Overclocking
June 3, 2009 3:32:01 AM

I don't think you're missing anything. IIRC, CPU-Z has a harder time being accurate with older hardware, so that could be the root of your problem.

I'm a bit confused though: do you have a clock speed for your OC, based on what your BIOS is telling you?
June 3, 2009 7:54:15 AM

No, by "BIOS calculation" I mean the result you get when you calculate the RAM speed using the memory:CPU ratio and the FSB.

The situation is still strange: I've tried overclocking the CPU to 2136 (FSB 267), with a RAM:CPU ratio of 4:3 (that would give me 200,25 to the memory instead of 200) and when loading Call of Cthulhu, the system just froze.

Neither at 2128 nor at 2136 the temp did not rise by more than 5 C. I'll have some more tests but I don't think 0,5 Mhz extra to the default RAM speed should make that big of a difference...
June 3, 2009 5:01:51 PM

Amd cpus have a integrated memory controller. They use a memory divider to set ram speed, depending of the ram type set in the bios. You don't just set the ratio like with intel s775 cpus. You need to research how to overclock amd cpus.
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