[coreboot] How to make graphical issue go away with 4GB of ram

Marc Jones marcj303 at gmail.com
Sat Jun 30 20:44:22 CEST 2012

On Sat, Jun 30, 2012 at 12:01 PM, Kyösti Mälkki <kyosti.malkki at gmail.com> wrote:
> On Sat, 2012-06-30 at 18:18 +0200, Denis 'GNUtoo' Carikli wrote:
>> Hi,
>> me and Kyösti Mälkki(kmalkki on IRC) figured out how to workarround the
>> following problem:
>> If I installed 4GB of ram in the m4a785t-m the screen comes up,however
>> it's black.
>> If I only installed 2GB of ram it worked fine.
>> I made a patch(I'll send it right after that email) but it seem to break
>> graphics for the case where 2GB of ram is installed.
>> So I wonder what would be the correct fix(a fix that would work for
>> every cases).
>> Explanation of the patch that will be sent right after the mail:
>> "basek - mmio_basek;" should be 1048576 (1G):
>> According to Kyösti Mälkki the correct value for the sizek is 1048576.
>> So I looked for what could create that size and found that.
>> I'm not convinced that "basek - mmio_basek" is the right fix but at
>> least we're in the right direction.
> My explanation of the issue: uma_memory_size must reduce the size of the
> last RAM resource _below_ 4GB. It now touches the last RAM resource,
> even if located over 4GB.

Yes, The UMA graphics memory is allocated in the lower 4GB. I think
that should be happening in mainboard.c. See the AMD reference



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