help with ram question

[Rick Stevens]

On Thu, 2007-05-31 at 11:51 -0700, Paula J. Lindsay wrote:
> Hi,
> I've just installed a fc5 machine.  He needs this rev because it is 
> compatible with his bruker software.
> Anyway, he already had 1 gig of memory in the machine, but when we put 
> another bank of memory (1 gig)
> we could not boot up.  We did a switch and they (both 1 gig dimms) and 
> they both work apart, but not
> together.  Has anyone ran into this problem?  I guess I could look on 
> fedoraproject.org to see if fc5
> supports 2 gigs of ram.  Anyway, any suggestions/advice/opinions are 
> appreciated.  Thank you in advance.

Fedora supports up to 64GB of RAM.  I have four machines running FC5
(yes, I know), each with 8GB.  I even have (gasp!) RHEL 3.5 machines
(2.4 kernels) running 16GB (hugemem kernel).

You didn't say where the boot fails.  Is it right after power up and/or
before the system tries to get to the hard drive?  If so, then you
really have a hardware issue!

If it fails before the grub "Loading linux xxxxxxx..." screen, I'd
suspect you still have hardware issues (grub doesn't need much RAM and
it doesn't care how much there is above what it needs).

If it fails after the initial nash signon messages, you may still have
hardware issues as NOW the Linux kernel is involved and memory will be
flogged harder than Windows does.  Remember, just because a system will
run Windows doesn't mean it'll run Linux.  I've seen many systems that
run Windows OK but die quickly under Linux or memtest86.  Boot off the
first CD and at the "boot:" prompt, enter "memtest86" and test the RAM.

As far as fault isolation is concerned, verify that the memory modules
are the same class.  Check your hardware docs and see if they should be
in adjoining or separate sockets (some systems require that).  Check to
make sure you're running the latest BIOS on your mobo.  See if you can
"slow" the machine down so the memory timing isn't as critical.

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- Rick Stevens, Principal Engineer             rstevens at internap.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
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-    Admitting you have a problem is the first step toward getting   -
-    medicated for it.      -- Jim Evarts (http://www.TopFive.com)   -
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