Re: Improve Video Counter???

[mjmahon@aol.com (Michael J. Mahon)]

aiiadict@gmail.com  (Rich J.) replied:

>mjmahon@aol.com (Michael J. Mahon) wrote in message
>news:<20041014173425.25357.00001280@mb-m22.aol.com>...
>>> This is beginning to sound like a very non-Apple II machine...
>
>How about a card:
>
>monitor acces to video RAM area, put data
>to a VGA monitor.  Watch the address bus and
>look for writes/ reads to $2000-$6000 for HGR
>and modify a VGA cards RAM buffer to reflect
>on screen what pixel has been modified.
>
>To make any new graphics system backwards compatible
>with 40/80/HGR/DHGR modes you are going to have
>to include hardware or software to provide these modes.

This is almost exactly what the SecondSight card did,
or attempted to do.

To emulate all those modes, which sort of "fell out" of the
clever Apple II design, required a microprocessor and a
fair amount of firmware, which seems never to have been
completely debugged.  ;-(

>VGA seems like a good option because it has a TEXT
>mode and cards are CHEAP.  Software written in CC65
>could be made to used to use the higher resolution,
>but I don't think anyone would be updating currently
>available software to use higher resolutions.

The VGA controller is cheap, but making it emulate the
standard Apple video modes requires a microcontroller
and firmware, complicating things immensely.

>Would it be possible to cut up an Apple IIe motherboard
>and eliminate ROMS, Video circuitry?  I think so.  You
>could use the address bus/ data bus/ peripheral bus
>as a BARE 6502 computer, run it at any speed up to the 
>EMF and part limits, and make cards to emulate old hardware 
>features/ROMS.  I've seen many 6502 manuals and books.
>It looks like this would be the quickest and cheapest
>way to get a fast upgraded Apple II into development.

Carving up an Apple is a poor way to get a fast, semi-modern
6502 system.  There are lots of much more compact and
faster ways to go.

Of course, it's a bit trickier to get a fast, semi-modern
_Apple II_ system, since the Apple II is much more than
another 6502 single-board computer.

>With a bare 6502 BUS and slots, It seems like it would
>be easy to watch the address lines and update a VGA
>buffer.  1 card with all ROMS, OLD video mode, paddle,
>disk II?, a slow 6502 for disk access, cassette etc.

All the required address and data lines are available
buffered and brought out to a connector on the peripheral
bus.  Anyone who wants to design such a card has
always been free to do so.

Perhaps it's not as easy or attractive as you think.

>new cards or maybe PCI adaptors to new hardware.

Shucks, why not just a new _computer_ while we're
at it.  ;-)

I continue to press my opinion that a classic computer
is interesting _because it's classic_, not because you
can use it as a base for a nuclear powered time machine. ;-)

Or, more to the point, if you want to design your own
computer, feel free to do so without calling it an Apple II.
I think that Woz did a _great_ job, including making it
the most _natively extensible_ machine that had ever
existed up until that time.

I love my 8MHz Zip Chip (which is unobtrusive both to
software and to the eye), my SCSI disk, and numerous
software extensions, but I draw the line at ripping out
large chunks of Apple II logic, emulating it in firmware,
and then calling it an "Apple II".

The wonder of the Apple II is that Woz used only a standard
6502 and a very small amount of simple hardware, and created
a machine of such power and versatility that it is still quite
interesting from both a user and an engineering perspective.

A VGA card is interesting from neither point of view.  There
is no application software to exploit it (as other than an
emulation of standard Apple II video), so a user is unsatisfied;
and the logical design of a VGA adapter is so over-wrought
and expansive that there is nothing to delight an engineer.

The only possible utility of such a thing would be simply
to adapt Apple II video to a VGA display, for which it is
monstrous overkill, and of dubious necessity in any case,
since NTSC monitors are ubiquitous.

For me, the proposition is exceedingly simple:  the only
video modes with software support are Apple II modes,
and that will never change.  So a VGA display will never
look better than a "fat pixel" version of standard Apple II
video (which I think looks worse than the real thing).

If someone thinks that they can change that--realistically--
then I'm all ears.

-michael

Check out parallel computing for 8-bit Apples on my
Home page:  http://members.aol.com/MJMahon/