CPU running at half speed - WTF?

I gave my brother one of my Shuttle systems which I had been using with a 2.6GHz P4. He put a P4 2.4GHz in it which was previously in his older system. Both Socket 478, but I don't know what revision.

The Shuttle system (FS51 mobo) is "jumperless" and setting the CMOS to default-like settings appropriate for the hardware installed and/or completely clearing the CMOS will cause the system to boot and report it's running at 1.2GHz (100MHz x12) at startup. Windows (system properties) shows the CPU as "Pentium 4 2.4GHz" and right underneath reports it's running 1.2GHz.

In the manual and on an identical Shuttle system/mobo, in the Frequency portion of the BIOS there's some type of multiplier setting that can be changed to 12 or 24, etc... I've never touched any of that stuff with any CPU I've ever put into those systems. It's always just autodetected and worked. Anyway, on the system I gave him that setting seems to be missing. And the other settings, don't seem to allow for anything other than getting it to come up at about 1.6 or 1.8GHz (changing some number between 100, 133, 150 and some CPU:Memory ratio to 4:3, 1:1 or 4:5)

I've never seen this before and have no idea what the problem is. We were trying to wrestle with a completely different problem (corrupted registry) so I didn't take time to do CPU swaps or anything to try and isolate the issue.

Any ideas, suggestions, anything?

Bruno

It sounds like the board doesn't support the exact CPU you have or maybe it does but it needs a bios update to detect it. Do some google searches for the exact CPU model and motherboard model and see what you get.

It sounds like the 2.4ghz processor he put in is a Pentium 4 2.4C processor. The C indicates that it is expecting a 200mhz bus (800 marketed number), something the FS51 can't do. The FS51 is limited to a 133mhz bus (533 marketed), or 150 overclocked.

(Grr, proxy at work died. SSH tunnel to the rescue)

What Tom just said sound like the most likely cause, but just in case it's something simple.... you didn't say whether you'd checked to make sure that the motherboard's BIOS was updated to the latest version. Sometimes support for certain CPUs needs a BIOS upgrade.

Thanks for the help guys. I thought the 800FSB chips were backward compatible with 400 and 533. Hmmm... I'll have him look for a new BIOS version. I suppose if it doesn't work out I'll just give him the 2.6GHz chip I have now and put his 2.4 into the older system he gave me.

Bruno

This is the problem on my FS41 board with an AMD Duron - we put in a 2500 only to find that the bus chipset did not handle the multiplier needed by the CPU, so only a 2400 or a 2600 would clock at full speed.

Moral of story: carefully read the CPU compatibility list on the Shuttle site for your MB before buying a CPU.