[GEM Development] New 256 colour driver

[Thomas Clayton]

Dear Thorsten:

1a) Make *sure* you have a VESA BIOS (Vn. ?1.2 or
2.0?) (or, for others with older cards, a VB extension
for your card). I'm pretty SURE that a PCI-buss Matrox
card *will* have a 'modern' BIOS 'built-in'.
1b) The Sw (device drivers in this case) is released
without warranty so ... we have to live with it - for
now.
2)The "guts" of GEM has *NOT* been RE-written to
'accommidate' 256-color states, so (remembering 1b)
we're 'lucky' that it "works' at all, IMO.

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. It seems my 'contemplation' of *how to*
"do" 256 colors would have been better spent on that
(1024x768) resolution rather than 640x480. 
(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).

Shane M. Coughlan" <shane at shaneland.co.uk> wrote:

> Thorsten is having trouble posting to the list, so I
> am forwarding this
> mail for him:
> 
> Hi!!
> 
> I have tried the new SD256 Vesa driver (OpenGEM
> Liberation Beta3 in
> an Dosbox Win98SE) and it's great to the screen
> resolution. It's the
> first opportunity for me to run more than 640x480 on
> my Matrox
> Millenium II (the "normal" GEM Vesa driver don't
> work properly. The
> screen is moved to the left).
> But I encountered some problems:
> - First the small one. The animation of the menus
> and windows
> sometimes look a little strange (the colors are
> flashing while
> drawing the menus). Maybe that's a "Liberation"
> problem.
> - When resizeing a desktop window/folder (for
> example the standart
> C:\gemapps) the system hangs if the window becomes
> to "big".
> - Basic2 don't runs anymore (it starts and before
> displaying anything
> escapes).
> - In Write.app the menu isn't accesible with the
> mouse anymore.
> - The whole system seems to become a little
> unstable. Sometimes
> shutting down with an windows error (illegal
> access).
> 
> And one suggestion: Maybe a 800x600 version of the
> driver would be nice.
> 
> Good work!!!
> 
> Greetings
>                 Thorsten



		
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