On Mon, Mar 9, 2009 at 1:18 PM, Louis Lagendijk <louis@lagendijk.xs4all.nl> wrote:
On Sun, 2009-03-08 at 19:27 -0700, John R Pierce wrote:
> Rick wrote:
> > In article <20090308031754.GA11794@bludgeon.org>,
> > Ray Van Dolson  <centos@centos.org> wrote:
> >
> >
> >> That sounds pretty strange.  Have you confirmed that removing the "new"
> >> memory allows you to run in runlevel 5 again?
> >>
> >
> > Yes, that's how I'm running right now.
> >
>
> now, try taking out the OLD memory and putting in just the NEW memory.
> see how it runs that way.   if this works, try with the new 4GB as the 0
> bank, and the old 2GB as the 1 bank.
>
> also, in the BIOS, check the memory timings, I'd leave them all on
> 'automatic' or 'default' or whatever the limited choices are in the
> Intel BIOS, trying to squeeze an extra clock out of CAS or whatever
> doesn't really help much under the best of conditions and it can
> destabilize a system under suboptimal conditions.
>
When you use 4 banks of memory, some boards require slower settings.
Tweaking the voltage may help there I guess, but I would opt for the
slower settings. I recall that my BIOS chose a slower memory setting
when I added 4G to my small server at home that already had 2G.... That
system has been rock stable (except for my Sun quad ethernet that had
problems with the Xen kernel due to MMIO issues. I solved that by
ditching the Sun card and using a vlan capable switch with vlan trunking
so that I no longer need so may ethernet interfaces)

Louis

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have you read your technical product specifications?
http://www.intel.com/support/motherboards/desktop/d975xbx2/sb/CS-029346.htm 
it states that the supported memory modules are only 2GB top

Table 4 lists the supported DIMM configurations.
Table 4. Supported Memory Configurations
DIMM
Capacity
Configuration
(Note 1)
SDRAM
Density
SDRAM Organization
Front-side/Back-side
Number of SDRAM
Devices (Note 2)
128 MB SS 256 Mbit 16 M x 16/empty 4 [5]
256 MB SS 256 Mbit 32 M x 8/empty 8 [9]
256 MB SS 512 Mbit 32 M x 16/empty 4 [5]
512 MB DS 256 Mbit 32 M x 8/32 M x 8 16 [18]
512 MB SS 512 Mbit 64 M x 8/empty 8 [9]
512 MB SS 1 Gbit 64 M x 16/empty 4 [5]
1024 MB DS 512 Mbit 64 M x 8/64 M x 8 16 [18]
1024 MB SS 1 Gbit 128 M x 8/empty 8 [9]
2048 MB DS 1 Gbit 128 M x 8/128 M x 8 16 [18]
Notes:
1. In the second column, “DS” refers to double-sided memory modules (containing two rows of SDRAM)
and “SS” refers to single-sided memory modules (containing one row of SDRAM).
2. In the fifth column, the number in brackets specifies the number of SDRAM devices on an ECC DIMM

 So your 4GB module is not supported... you should use 4x2GB modules in order to see an improvement(always using pairs, remember it's dual channel).

cheers


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