riscy
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Re: Video subsystem...

To: mackinla@cs.curtin.edu.au
Subject: Re: Video subsystem...
From: Stephen Siu-ming Wong <a080700@hp750a.csc.cuhk.hk>
Date: Sat, 26 Jun 93 14:41:46 HKT
Cc: riscy@pyramid.com
In-reply-to: <199306251447.AA26313@vincent.cs.curtin.edu.au>; from "Patrick Mackinlay" at Jun 25, 93 10:47 pm
Mailer: Elm [revision: 70.30]
Hi Risciers,

>The other option that I think has some merit is to use the TMS34010.
>This chip used to be pretty expensive, but I think it's dropped a lot
>since the last time I looked. The advantage with this chip is not so
>much speed, but simplification of the overall design. Depending on
>the price of the actual device, I think it could be one way to make
>the video section pretty cheap. I've been told by some other guys
>that it's quite easy to deal with as far as integration with the main
>CPU is concerned (that's what it's designed for, after all!). I have
>a few concerns that it might mean putting another ROM on the board,
>but that might be cheaper and easier than other solutions (I think
>it's got dynamic bus sizing stuff on-board in any case).

I strongly opt for TMS34010/020 solution, as they are CPU and any
one of them will greatly enhance the performance of X.  There
shouldn't be an extra ROM, every thing should be boot strap from
the main CPU, just add some extra object code file on the main
CPU EPROM, and let the main CPU to initial load the TMS CPU.  The
initial TMS code shouldn't be very complicated, it should handle
the most basic text mode only, and let linux (or whatever OS) to
put some still advanced (and large) code on the TMS CPU.

Moreover, VRAM solution should give the best performance (Video
wise and system wise).  2-4MB should be enough for TMS code +
cache (font/pixel/etc) + frame buffer (assume 1024x768x256).

I don't mind if opt for less cost, choose TMS34010, although it is
not the best performer, but it is really cheap.  Of course, it will
be the best to be able to swap in a TMS34020 by users.

>BTW: There's a possibility the ET4000 or other VGA chips come in
>non-SMT versions, but I'd personally prefer to stay away from them.
>As far as I can see, the best way to slow a video system down is
>to stuff it through a VGA chip...

Please, DON"T consider ET4000 chip or TVGA or whatever VGA chips, they
are brain damage.  They are designed for the limited ISA bus and Intel
segment architecture!  If we want on-board video, why should we deal
with such inferior technology!  I want a real (and fast) video system!

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