coreboot support for AMD HT3

[Scott Duplichan]

Hello,

I am having trouble getting high resolution UMA graphics modes to work
on my RS780/SB700 system. I am using coreboot project mahogany_fam10.
EDID is working. Both VGA and DVI connections have the problem. At
1600x1200, 16-bit color is almost perfect. But the same resolution with
32-bit color results in a display that jumps so much it cannot be read.
Why would 32-bit color make a difference? I am thinking that refreshing
1600x1200 pixels 60 times per second takes a lot data, and that data
has to cross the HT link. True color takes more data than high color,
and true color may be exceeding the capacity of the cpu-RS780 link.
The link is running at the slowest possible setting, 200 MHz, 8-bit.
Question: I see all the code in place for HT3. What is the status
of coreboot support for AMD HT3?

Thanks,
Scott

[Peter Stuge]

Scott Duplichan wrote:
> At 1600x1200, 16-bit color is almost perfect. But the same
> resolution with 32-bit color results in a display that jumps so
> much it cannot be read. Why would 32-bit color make a difference?

Twice the bandwidth needed to get the graphics data out of RAM.
> I am thinking that refreshing 1600x1200 pixels 60 times per second
> takes a lot data, and that data has to cross the HT link. True
> color takes more data than high color, and true color may be
> exceeding the capacity of the cpu-RS780 link. The link is running
> at the slowest possible setting, 200 MHz, 8-bit.

Ouch! :\ That would seem to cause the problem.

Can't say about HT3 I'm afraid.

//Peter