5 Mar
1999
5 Mar
'99
2:18 p.m.
Derek wrote:
Exactly why isn't it VGA-compatible?
The 34010 isn't even *similar* to a VGA. The exact extent of the
compatability is that both hook up to a host processor, and both produce
a video output.
I thought that certain things are true of the 34010:
- flexible memory architecture
If a large flat address space is a "flexible memory architecture",
then the 34010 certainly has it. However, that isn't what VGA uses. VGA
has all sorts of crufty bank switching and other disgusting hacks.
- many operations done in software (not hardware)
Actually most of the interesting operations of the 34010 are done in
microcode. But those operations aren't similar to VGA.
- some hardware (video RAM, shift registers and other
parts to
actually produce a monitor signal) external to the 34010
Yes.
It's certainly possible to emulate the Hercules,
CGA, and MDA. Is there
some lack of configuration registers, or some internal timing constraint,
that makes emuilating the VGA impossible?
The 34010 doesn't have any built-in support for emulating any of those things.
Sure, you could do it by adding a big pile of external logic (which you could
put into an ASIC, or some PLDs). Due to communication overhead, it would
be a fair bit slower to emulate a VGA with a 34010.
It's cheaper and easier to just put a VGA controller on the card, since that
does exactly what you need in a single inexpensive chip. Leave the 34010
to doing what it does well. For example, acting as a display list processor
for AutoCAD. The VGA interface is too low-level and baroque to be
efficiently emulated in software.
Eric