> For the S3 cards you have to know: How much videoram you have, how fast
> the videoram is (ram-timing) and what other timings are needed for that
> particular manufacturer's card... BTW : this info is generally not all
> that easy to get.... [though iirc most videoram is of common speed]
additionally there is video ram type (FP, EDO, SD, SG), split transfer settings
for VRAM, precise timing/length of DRAM signals (ras/cas/ow etc.) and so on
which differ between vendors (and sometimes they have to be different for
cards with _identical_ chips just because of board layout etc.!).
for some recent chips you even can select the fan out for the line drivers
for some DRAM signals depending on how many chips you've installed on your
card and how this memroy is organized (how many banks etc), there are
PCI timing/controlling things and more ther fun;)
if you can't test every board release for every card/model/vendor yourself
there are two possible approaches:
1) use some (probably conservative) guesses for initialisation values
and cross fingers that this is working reasonable with other cards too
(and accoring to my experiance from XFree86 feedback with S3 cards
it will _not_ work for a wide number of `other' S3 cards).
2) let the BIOS do the initialisation job for all this hardware stuff.
here I see two possible ways:
2a) first, install every card as single card and capture all register settings
(esp all the hardware stuff) and then use _this_ saved data as startup initialisation
for 2nd, 3rd etc. video card. this one is pretty easy to programm,
but a bit nasty for users (and there'll be many pitfalls for new users...)
2b) disable 1st vga card and it's BIOS via PCI configuration, then enable
2nd video card and it's BIOS and then call this BIOS to initialiaze
this card (e.g. using very stripped down DOSEMU, or using the
x86 and BIOS emulation code which is used e.g. for DEC Alpha boot loader MILO
for Linux/AXP).
Harald
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Harald Koenig, \/\/\/\/\/\/\/\/\/
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