One CPU core 'disappears' after overclock...

[oddity21]

I have an E6600 running on an ASUS P5B-E. Today, I decided to push my rig a little and pushed the CPU to 325x9 at 1.4v. Somehow, the BIOS message "Core: 2" was gone and Device Manager reported only one CPU. 3DMark06 CPU test score dropped from 2080 to 1300-ish, essentially proving that only one core was up and running. Even Core Temp only reported the temperature of Core 0.

Thinking I had broke something, I quickly reverted back to stock settings and the core just came back like nothing had happened! Ran the CPU test again and got 2090.

What's going on with me? Is there anything faulty in my rig?

 

[nyker96]

this sounds strange never seen this type of thing here in the forum. I say it's some driver issue.

 

[oddity21]

Yeah, I've been trying to get help everywhere without success. Usually a Google search turns up solutions to any problems, but nothing comes up at all with this.

 

[Agent11]

To use 2 or more cores you need APIC enabled (same to use HT on P4's).
Turn it back on.

 

[ataws]

I have a very similar problem but with Athlon 4800+ on Abit Ax8 board. 2 cores visible until I adjust the cpu multiplier and then 1 core disappears. I can overclock by increasing fsb and still have 2 cores... just as long as I don't adjust the CPU multiplier.

 

[A554SS1N]

If it disappeared at the BIOS screen, it's either a setting in the BIOS, a general motherboard fault, or a CPU fault.

 

[ataws]

I doubt it's a cpu fault, I can OC fine with 2 cores by simply increasing the FSB - if I run everything at stock but reduce multiplier from x12 to x11 then surely the result should be 2 cores running at 2.2ghz rather than the default 2.4ghz - I get the 2.2ghz but with only 1 core visible - how can underclocking lose a core?

I was wondering if oddity21 also loses a core simply by reducing the CPU multiplier and leaving everything else at stock?