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RedHat 4.4 on DL380 G4 detects only one CPU

NirY
Occasional Visitor

RedHat 4.4 on DL380 G4 detects only one CPU

We have a Red Hat Enterprise 4.4 SMP installed on a DL380.
We noticed that the kernel detects only one CPU out of two physical CPU's.
/proc/cpuinfo shows just one (1), while dmidecode and the BIOS screens at startup show that there are two (2) CPU's.

Basically, all this shows me that the kernel fails to detect the second CPU, and that the BIOS detects both.
So - what now? how do I make the kernel realize that there are two?
6 REPLIES
NirY
Occasional Visitor

Re: RedHat 4.4 on DL380 G4 detects only one CPU

Addendum - there are no messages in dmesg or /var/log/messages about any failure to start the second CPU. in fact, they show a successful start of one CPU and no tries to start a second CPU.
Mike Stroyan
Honored Contributor

Re: RedHat 4.4 on DL380 G4 detects only one CPU

The dmidecode report may be showing a second CPU for what is really hyperthreading on a single CPU. That reporting of disabled hyperthreading as an unused CPU can be very confusing. You can enable and disable hyperthreading from the BIOS to see what reaction the kernel has to that.
Ivan Ferreira
Honored Contributor

Re: RedHat 4.4 on DL380 G4 detects only one CPU

If the OS type is not correctly selected in the BIOS, you can have this kinds of problem. Ensure that the OS type is correctly selected.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Steven E. Protter
Exalted Contributor

Re: RedHat 4.4 on DL380 G4 detects only one CPU

Shalom,

Could actually be a bad CPU.

Ideas:
1) Make sure hyperthreading is enabled in the BIOS.
2) Change OS type back to default.
3) Run hardware diagnostics from the bootable GL380 CD. Update the firmware while you are at it.

SEP
Steven E Protter
Owner of ISN Corporation
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Founder http://newdatacloud.com
NirY
Occasional Visitor

Re: RedHat 4.4 on DL380 G4 detects only one CPU

Thanks for your answers.
Here are some more bits of info:

Mike - There are two physical CPU's - I've checked that personally by opening the chassis.... so it can't be hyperthreading. Furthermore, the dmidecode info shows two distinct ID's, and with hyperthreading you get one ID only.

Steven - Both CPU's work fine when inserted in slot 1. So I don't think they're defective.

However, I will check the rest of your suggestions - have to say I'm not sure what you mean by "Ensure that the OS type is correctly selected" (Mike), but it sounds like a good idea :-)

and if anyone has more ideas I'm still looking for them. If these suggestions don't work I might have to shut the server down and try a fresh install - I really don't want to do that.

I might even have to try Windows (Gah...)
Don Vanco - Linux Ninja
Regular Advisor

Re: RedHat 4.4 on DL380 G4 detects only one CPU

To possibly state the incredibly obvious... You're aware that the info in /proc enumerates starting with "0" - right? So a 2-way will show CPUs 0 and 1....

Have you tried any other releases on this system? Perhaps boot a Knoppix CD and see if you get 2 penguins right from the start? Perhaps an alternate SMP kernel in 4.4 (hugemem, etc)?

Don