[coreboot] How to test RAM beyond 640 kByte boundary
Marc Jones
Marc.Jones at amd.com
Wed May 21 18:08:20 CEST 2008
llandre wrote:
>>>> Why is the RAM physically unaccessible beyond 640 KByte at this stage?
>>> Which chipset / board? It's not necessarily unaccessible.
>> AMD Geode LX/CS5536
> I forgot to mention that is a custom board.
>
>
The 640-1MB area is covered by a basemask descriptor (A0000-BFFFFh)
setup and used by graphics and a swisscheese descriptor (C0000h-FFFFFh)
for the legacy shadow memory hole. In
northbridge/amd/lx/northbridgeinit.c see the gliutables structures.
In both tables you could change the swisscheese to allow reads and
writes to memory like this:
{.desc_name = MSR_GLIU0_SHADOW,.desc_type = SC_SHADOW,.hi = MSR_MC +
0xFFFF,.lo = 0xFFFF0003},
Marc
--
Marc Jones
Senior Firmware Engineer
(970) 226-9684 Office
mailto:Marc.Jones at amd.com
http://www.amd.com/embeddedprocessors
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