[BULK] RFC: Generic shadow mechanism useable from a payload

[Adam Sulmicki]

>
>> But I actually think that is overkill. v2 by default and design
>> enables all of the shadow ranges as memory.  So we just need to
>> use those ranges.  That should be much easier having to patch
>> ADLO each time.  It is fairly unlikely a writable ROM segment is
>> going to break anything.
>
> FWIW, I actually do remember someone on the list saying that they had to 
> disable rom write since the things DID break otherwise... anyone else 
> remembers more?

it was in context of ollie's work, not adlo:

Date: Thu, 13 Jan 2005 16:38:47 -0600
From: Richard Smith <smithbone at gmail.com>
To: LinuxBIOS <linuxbios at clustermatic.org>, YhLu <YhLu at tyan.com>
Subject: Re: Running with VGA

> > it from normal BIOS, it will skip some operation. In this case,
> > it is probably init font buffer.
>
> I have word from an ATI tech who says they don't do that.

I should clarify this.  I thought you guys were talking about zeroing
the entry pointer so that if you copied it from ram you would not get
a working copy.

Buy yes the ATI bios looks for a bit already set and if so then will
skip RAM init and various other things.

My copy checks to see if it can write the into the shadow space before
it self-modifies and if not I believe it tries to use some bits in the
CMOS.  So if you disable writes to your c000 shadow you might trick it
to not skip things.