Hello all,

I've got a computer which used to run CentOS 5.1 flawlessly. Unfortunately, I installed some new modeling software which wasn't RH 5.0 compliant and began getting segmentation faults.

At the behest of the new software's tech support, I downgraded to CentOS 4.6 and have had nothing but trouble ever since.

Some info: I'm running on a supermicro motherboard with two, dual core AMD opteron (so, 4 processors).

After installing CentOS 4.6, the computer began to freeze between 10 and 30 seconds after logging in. After much trial and error, I realized the computer would not freeze if I logged into the UP (uni processor) kernal. Which is great, but really reduced the functionality of the comptuer (we do fluid flow modeling and need the parallel processing option).

After asking some questions at the CentOS forums, I was instructed to try and boot into the smp kernal with noapic. This allows the computer to run with all four processors, but the performance is poor. The computer will hang up briefly every 10 to 30 seconds. So, the computer is maddeningly choppy and maddening to use.

So, long story short, since my computer ran fine with CentOS 5.1, I'm assuming there is a version of APIC out there which works with these processors. Is there anyway to upgrade to the newer version of APIC?

Thanks!

Here are a few basic ideas that might help anyone having trouble with CPU or motherboard driver problems.

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First download the latest chip drivers for the motherboard and install them. (Flash the motherboard BIOS). You can get these from the motherboard web site. They are not OS specific although you may need to run Windows to install them. Hopefully they can be installed from a boot floppy or something similar. If not then just shove a Windows disk into this computer long enough to flash the motherboard BIOS, then reconnect the Linux disk.

Then get into the motherboard CMOS setup and turn off APIC and ACPI. Look around in the motherboard's CMOS setup for other motherboard features that can be turned such as suspend to ram.

Make sure that the motherboard is set to use the latest version of SMP management. I don't recall off hand what that version is but the number 1.4 comes to mind.

Make sure that the motherboard manages IRQs. Some motherboards do more in this area than others. Check to ensure that the other protocols such as USB and LPT are set to use the latest version or are turned off.

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Now as for Linux, if the CPUs are 64 bit then consider whether you want to use a 64 bit kernel or a 32 bit kernel. If you have a choice you may want to select the one that you are currently not using.

Make sure that the version of CentOS/Linux has all of the latest driver patches available for that kernel version.

See if you are running special function software such as athcool. Turn it off.

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Hopefully you can see the method that I've got in mind. Make sure that the motherboard drivers/BIOS are up to date, then make sure that the motherboard settings aren't getting in the way, then make sure that the Linux drivers are up to date. Simplify your software environment until the problem goes away, then add back only what you need.

Or change Linux distributions.