[CentOS] segfaults with 8 gig of ram

Morten Torstensen morten at mortent.org
Sat Mar 24 11:10:02 UTC 2007

John R Pierce wrote:
> I do think a 64bit version of memtest86 would be a good thing...   I'm 
> unclear how a 32bit app could test memory above about 3GB unless its 
> playing the PAE game (3GB because in a 32bit system, the PCI bus 
> peripherals take about the top ~ 1GB for their I/O space, so the ram has 
> to be mapped to a higher physical address, only accessible via PAE...

Yea, addressing is one issue, but I have seen problems on 1GB machines 
too. Mind you, memtest is probably right and the memory modules probably 
were ok. It is some combination of chipsets, memory and linux in 64-bit 
mode that stress parts of the entire memory system. That is what memtest 
is unable to detect. Few people run in 64-bit mode compared to 32-bit... 
still some snags to work in the chipsets/memory I guess.

In real life a "while true; compile kernel; done" loop would panic the 
kernel in 10-30 minutes. Memtest didn't find problems. Changing memory 
modules to a different brand or lowering clockspeed made the system stable.

As for 32-bit and testing... remember there is a big difference between 
address space and memory. You would just map the memory in the 4GB 
address range and test it, same method as you would do with PAE mapping 
- up to 64GB. But that is still big enough for most people :)


//Morten Torstensen
//Email: morten at mortent.org
//IM: Cartoon at jabber.no morten.torstensen at gmail.com

And if it turns out that there is a God, I don't believe that he is evil.
The worst that can be said is that he's an underachiever.

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