Trouble with Asus SK8V MB with more than 2048M memory

[Matti Pulkkinen]

Bryan J. Smith kirjoitti 08.04.2006 kello 16:21:
> On Sat, 2006-04-08 at 10:41 +0300, Matti Pulkkinen wrote:
> > I can't use more than 2048M of memory in my test machine. 
> > The machine has AMD Athlon 64 FX with 4096 M of
> > physical RAM with Asus' SK8V Motherboard.
> > I use two 2048M modules, Kingston's KVR266X72RC25/2G.
> 
> I've got a theory, remove one DIMM.
> Do you get 1GiB now?  ;->
> 

Thanks for good ideas, Bryan.

I actually tried that. With 2 x 2048M FC 5 says it uses 1.9 GiB memory. When I removed the other module, ceteris paribus, FC reported, that it has 2 GiB of RAM. Pretty counterintuitive, I think.

With the 2 x 2048M chips I tried to play with the MEM parameter. To set it to 4096M when starting FC 5 didn't increase the amount the memory, but it didn't cause a kernel panic either. That was more than with some other distros.

I booted with Windows XP x64 edition and it reported the amount of memory correctly.

 (I haven't tried to allocate more than 2048M continuous slice of memory in Win x64. With a small assembly routine it would be quite easy to tell, if there is some kind of gap in the address space somewhere near 2 GiB, but this is a Linux group and I'm not very fond of off topic posters)

> Yes, but I've always used four (4) 1GiB DIMMs to avoid lack of 2GiB DIMM
> support (and only getting half the memory).  I typically get 3.5-3.6GiB
> due to the hole sub-4GiB for memory mapped I/O.

SK8V gives you an option to control the hole by the means of the BIOS. My tests with that feature have not helped me with Linux.

I'm not a big Linux hacker, but if someone could give me a  hint which part of the kernel code I could start looking for the reasons behind the problem, I would be very grateful.

By the way, the Asus SK8V has some pretty odd features that don't work either, like Wi-Fi slot for a proprietary IEEE 802.11b card. They don't sell the product actively any more. No I know why.



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