10 Aug
2012
10 Aug
'12
4:56 p.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Chuck Guzis
Sent: Friday, August 10, 2012 5:43 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: X Window server for NEC 7220
On 10 Aug 2012 at 16:09, Andrew Lynch wrote:
The
Hi! The goal for the S-100 VGA board is to make
a register compatible
SVGA that uses commonly available VGA monitors. The application would
be an X server for the upcoming S-100 80386 CPU board. Also to
provide a greater degree of PC/XT/AT compatibility for the S-100
80286, S-100 8086, and S-100 8088 CPU boards. Presumably, an S-100
SVGA board would also be usable by non-Intel x86 CPU boards as well
but that is optional. If VGA is not viable then we need to explore
other options to provide a bitmap display for the X server.
Hi Andrew,
It's not hard to get to VGA scan frequencies without using a VGA chip. AT&T 6300 did it using nothing more than a
modified CGA card. Your design
might be limited to 16 colors using nothing more than a 6845 CRTC, but if
the
goal was a simple 640x480 display, that might be
enough.
It all depends upon what you're willing to settle for.
--Chuck
Hi Chuck! Yes, that's probably true assuming there is a 6845 clone that is
fast enough. However a custom S-100 MC6845 video board that's not VGA
compatible has the same lack of software problem as the S-100 uPD7220. I
already have a known working ECB uPD7220 board that works great and is
compatible with VGA monitors. Adapting it to the S-100 bus turns out to be
a relatively easy problem since it is an IO port only design. It is very
simple and it is essentially ready for prototype boards right now.
What a VGA compatible design brings to the table is the installed base of
legacy software for the PC. It would be much easier to adapt an existing PC
Linux X11 implementation than to start from scratch with a completely new
board. It looks like the former option may be our only choice though.
I would think a X Window server without acceleration for the NEC uPD7220
would be about the same speed for a basic VGA. There is nothing I am aware
of on the basic VGA that makes it particularly fast. Hardware BITBLT was
not introduced until the VGA accelerators came along years later after the
original VGA was introduced (1987 IIRC).
Thanks and have a nice day!
Andrew Lynch