DIMM relocation on Tyan S2885

[Matt Harvey]

Hello,

I have an Opteron machine based on the Tyan K8W S2885 mainboard which is
equipped with 8GB of RAM (8x1GB DIMM). The BIOS is mapping  the PCI/AGP
devices into the address space immediately below 4GB and so
consequently, I am losing access to nearly an entire 1GB of RAM. I've
spoken to Tyan about this and they acknowledged that it it is principle
possible for the BIOS to remap the DIMM presently located at 3GB to 9GB
but that they have no intention of including this option in their BIOS
as it "penalizes 32-bit OS's that cannot use more than 4GB."

So the question to the panel is: Will LinuxBIOS solve this problem for
me? The task this machine was purchased for really does require as much
RAM as possible.

Thanks in advance,

Matt Harvey

Matt Harvey  writes:
> Hello,
>
> I have an Opteron machine based on the Tyan K8W S2885 mainboard which is
> equipped with 8GB of RAM (8x1GB DIMM). The BIOS is mapping  the PCI/AGP
> devices into the address space immediately below 4GB and so
> consequently, I am losing access to nearly an entire 1GB of RAM. I've
> spoken to Tyan about this and they acknowledged that it it is principle
> possible for the BIOS to remap the DIMM presently located at 3GB to 9GB
> but that they have no intention of including this option in their BIOS
> as it "penalizes 32-bit OS's that cannot use more than 4GB."
>
> So the question to the panel is: Will LinuxBIOS solve this problem for
> me?  The task this machine was purchased for really does require as much
> RAM as possible.

At the present moment that is not implemented by LinuxBIOS.  It is
something I would like to work on, but it has not been a priority yet.
I think I could do it a day or two a week with testing etc.

There are a couple of ways LinuxBIOS could solve this problem.

1) You have the code so you can implement that, so you are not helpless.
2) You can wait until I get around to implementing for other reasons.
3) You can pay one of the vendors doing LinuxBIOS to fix it for you.
   <plug> Linux Networx </plug>

Eric

[ron minnich]

On Sun, 11 Jan 2004, Matt Harvey wrote:
> So the question to the panel is: Will LinuxBIOS solve this problem for
> me? The task this machine was purchased for really does require as much
> RAM as possible.

well, I think we can solve it for you. I have one of these boards, if you 
want to do the homework on how to do it I'll try to do it.

ron

ron minnich  writes:
> On Sun, 11 Jan 2004, Matt Harvey wrote:
> > So the question to the panel is: Will LinuxBIOS solve this problem for
> > me? The task this machine was purchased for really does require as much
> > RAM as possible.
>
> well, I think we can solve it for you. I have one of these boards, if you 
> want to do the homework on how to do it I'll try to do it.

There are a couple of ways to implement this.  If you have less than
4GB in one of the cpus you can put that cpu below 4G and the rest about.

Alternatively you can not enable dimm row interleaving, and create
a hole in a single cpus memory map, but putting the base address for
all but the first dimm rom about 4GB.  This looses a little performance
though.

And on the extreme side I think it would be possible to place all
of memory about 4GB and to use the GART to get a little of it to
appear below 4GB.  If this works there are still some very interesting
issues that crop up when the OS takes over the GART, and reprograms
it.

Eric