[coreboot] BIOS RAM in AMD SB7XX southbridges ?

[David Hendricks]

On Tue, Oct 27, 2009 at 6:06 AM, Darmawan Salihun <
darmawan.salihun at gmail.com> wrote:

> What is the BIOS RAM in AMD SB7XX used for?
>

Looks like scratchpad memory to me. From the public
doc<http://developer.amd.com/assets/43366_sb7xx_bdg_pub_1.00.pdf>
:

3.3 BIOS RAM
The SB700 has 256 bytes of BIOS RAM. Data in this RAM is preserved until
RSMRST# or S5 is
asserted, or until power is lost.
This RAM is accessed using index and data registers at CD4h/CD5h.

Might it be enough to act as a very, very small cache-as-RAM substitute
until CAR can be set up?

On Tue, Oct 27, 2009 at 6:06 AM, Darmawan Salihun <
darmawan.salihun at gmail.com> wrote:

> Is it to buffer the BIOS contents from SPI flash chip prior to
> execution of the very first instruction?
> I recall that it's impossible to execute code directly in an SPI chip.
>

That's correct, afaik.

-- 
David Hendricks (dhendrix)
Systems Software Engineer, Google Inc.
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