[GEM Development] New 256 colour driver

[Thomas Clayton]

BTW John,

I don't know if I mentioned it but I have an IBM
*Technical Connection* RO-DAD that has many IBM
drivers - and such - on it. I haven't looked at it
again, since your 8514/a letter some weeks ago but
it'll probably have all sorts of 8514/a related Sw on
it. I *know* it had *some* 8514/a Sw because it is
where I 'made' (*.dsk file ---> diskette) my 8514/a
diskettes from. I've got the diskettes but *not* the
8514/a *card*, anymore. That's not really so bad as I
*do* have an XGA card and diskette ('home-made',
again). 

It's an XGA(-1) - as far as I know - *NOT* an XGA-2
with the unusual 'feature' of having Vid.Mem. Upgrade
sockets on it. They take 'zig-zag' chips (ZIP vs DIP)
and require four more to make a Mega-B. The XGA(-1?)'s
usually had *only?* 512KB w/o upgrade capability,
AFAIK. It's currently *not* in use since the MCA
system I have - gotten second hand, of course - had a
Reply Corp. 80488x2 (50MHz) upgrade board with a 1MB
Cirus Logic 5426 video 'built-in'.

Anyway, I'll have look - hopefully by the end of the
month (by which time I hope to be 'On-Line' from
*home* again!) - and let you know what I find.


Just 'cause I typing:
LAst weekend I 'dug out' my copy of Ferarro; copy of
Wilton; and a book about the Hercules IN-color card -
a non-starting standard since some firm called IBm
came out with something called VGA at the same time! -
in response to your success. BTW, these were the
"bibles" of video card programming in the late '80's
early '90's. I 'blew' my mind looking thru the chapt.s
in Ferraro detailing all the different SVGA chipsets.
Then I read the chapt. 'announcing' the VB committee
was going to set up some standards. I became 'sane'
again at that point. I also, got hope back that maybe
a set of 256 color drivers for GEM would be possible.
I'd suggest we get the SciTech 'kit' while it is still
available (and free for use). No support, fof course.

Which gets me(us) back to the origianl question(s).
You said you used DOS-EMU to create the driver. Might
it be that someone with REAL V B Exten.s could have a
'glitched' session while you didn't / wouldn't?

HEY, that's a good place to quit.

Bye for now,

Tom Clayton



--- John Elliott <jce at seasip.demon.co.uk> wrote:

> : 3) I'm somewhat surprised, myself, that the first
> -
> : and second! (thanks, John) - 256 color drivers
> were
> : for 1024x768 and *not* 640x480 -- till I read
> John's
> : README file.
> 
>   My explanation only applies to my own SD256, not
> the 256-colour 8514/a
> driver. For more on that, see below.
> 
> : (This has to do with the way the bytes 'line up',
> and
> : are accessed, in video memory 'space' at one rez
> : versus another. This, in turn, is related to real
> mode
> : ONLY being able to access a 64KB (not more than
> 128KB)
> : "window" of video memeory at a time. Addresses A0
> 00
> : to AF FF or, up to, BF FF (Hex-a-decimal
> numbering).
> 
>   Some VESA BIOSes (not DOSEMU, which was what I was
> developing on) allow 
> two 64k windows into video RAM, one at A0000 and one
> at B0000. 
> 
>   Now, 8514/a is a different kettle of fish. Unlike
> just about every other
> video card on the planet, it doesn't appear in
> memory at all. Everything's
> done by sending drawing instructions to I/O ports
> (though I'm not clear if
> that's also the case for bit-blitting, or whether
> the card can directly
> access motherboard RAM for that). Also unlike
> everything else, it really
> does have eight planes rather than packed-pixel
> memory.  So there's no
> technical reason why the Paradise driver couldn't
> have supported 640x480. I
> suspect that the reasoning was that someone who
> bought an 8514/a clone
> bought it because they wanted 1024x768x256
> resolution, so that's what the
> driver did.
> 
> -- 
> John Elliott
> _______________________________________________
> gem-dev mailing list
> gem-dev at simpits.org
> http://www.simpits.org/mailman/listinfo/gem-dev
> 



		
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