10 Aug
2012
10 Aug
'12
3:55 p.m.
Andrew wrote:
However, implementing an SVGA on the S-100 bus is a
non-trivial
exercise as well.
What a surprise, that implementing SVGA that was developed in the
late
1980s would be difficult using 1970s technology.
even just finding a chipset that is compatible
with the S-100 bus has proven to be extremely difficult.
Another big surprise, that
chips designed for 2000s buses are hard to
use on 1970s buses.
We've resorted to
using the Propeller
The Propeller is not going to get you anywhere for this
project; it's
good for some things, but this isn't one of them.
and even an FPGA (Spartan 3) based approach but none
provide the low level VGA compatibility or even a usable bitmap graphics
mode.
There's no reason an FPGA can't provide VGA compatibility or a usable
bitmap graphics mode. I've done several bitmap graphics projects in
Spartan 3s without any difficulty to speak of, though I wasn't trying
for VGA compatibility.
If you want to build a VGA controller without using a VGA chip, then you
have to build a VGA controller. There's no way around it.
If you or anyone else has some insight on how to
implement a register
compatible SVGA on the S-100 bus I am very willing to listen!
There are only two (somewhat) practical approaches: use a VGA chip
(such as the CL part you tried), and somehow kludge it onto the S-100
bus, or use an FPGA. Neither approach is easy, but that's because VGA
by its nature is complicated. It's the same reason you won't find
"Quantum Electrodynamics for Dummies" at your local bookstore or library.
Of the two, using the CL part should require less engineering, since
designing a bus interface is two or three orders of magnitude less
complex than designing an entire VGA controller.
What problem did you run into with the CL chip? Were you using it in
ISA-bus mode? Since it is a bus slave only, it doesn't seem like it
should be that difficult to talk to it.
Eric