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Re: FPGA musings
Jorge Chamorro Bieling wrote:
Michael J. Mahon <mjmahon@aol.com> wrote:
Jorge Chamorro Bieling wrote:
Sean Fahey <a2fan@hotmail.com> wrote:
There is a 4MHz Zip Chip on eBay right now.
hehe $102, and going up, and 5 days left...
Can someone please re-design a zipchip with a fpga (this time with more
than 8mhz).. ???
It looks like the price isn't going to be a problem.. :-)
While everyone seems to be getting off on the idea of putting lots
of fancy stuff into FPGAs, there is something that needs to be
considered...designing complex hardware is no easier (and arguably
harder) than designing complex software!
It's a lot more than a weekend project to design a Zip Chip. ;-)
This can't be called "complex hardware", it's not at all by todays
standards. You see, there are too many, more complex, pipelined
microprocessor ip cores designed by individuals *just for fun*.
Nowadays these hdl things let you comfortably "write" hardware that you
can put so easily in silicon...
It has nothing to do with the good old way of lotsOfDatabooks +
lotsOf74lsxx + pen + paper + drawingSchematics + karnaughMapping +
checkingDelays + checkingFanOuts + protoBoarding + wireWrapping +
soldering + oops! + correctThis + watchForGlitches + watchTheNoise +
connectFloatingInputs + haveaLookWithTheScope + burnTheEPRomAgain +
someMoreDecouplingCapacitors + etc etc. Most Ataris and Commodores have
been already fpga'ed just for fun.
The apple2 community is not up to date in this sense... :-(
To make it easier the 6502 could be left out of the fpga by using an off
the shelf WDC part. Then only cache/glue/sinchronization logic would
have to be designed , hdl'ed (written!) and fpga'ed. You would get at
much 14x the speed though. Maybe use a 6502 ip core for more speed. Or
use a readily available risc ip core and emulate the 6502 in software. C
sources are readily available. Or who knows what, there's people that
knows so much more than I. But I don't see any essential thing I'm
missing here. It looks so plausible.
As does travel to Mars... ;-)
Of course, one would try to avoid re-designing the 65C02.
Perhaps you didn't know that it took several tries to make a Zip Chip
that worked with almost everything--and it still doesn't. (Some of
the problem is just using the processor interface, since DMA can't be
seen from there.)
And it was preceded by the McT SpeedDemon, whose design was a kind
of prototype for the Zip Chip.
Of course, "turns" are easier now, but testing is still a bear.
The stakes would be a lot lower, though, if revisions could be emailed
and downloaded in the field. ;-)
In fact, it's a perfect project for people that have the time, that have
the know-how, that spend the time reading daily things like
comp.sys.apple2, people like... you. And probably others like you that
are also coming here to comp.sys.apple2 often but for some reason don't
seem to talk much. Maybe some people who designed apple2 things in the
past... who knows.
Jorge, I understand about the "software-like" modern hardware design
cycle. What I was saying is that there is still substantial complexity
in the design of something like an accelerator. Much needs to be
considered to produce a fully compatible design. (This is why the
RocketChip design was ripped-off, rather than re-designed. ;-)
Remember, we're talking about one person, spare time here...and you
need a combination of ability and motivation that is non-trivial.
For myself, I have other projects that interest me more than replicating
the Apple II in modern hardware, though something might change that in
the future. For the time being, my *real* Apples are just fine, and
allow me to spend my time in other ways. ;-)
As I said, I'd like to see it, too, but I don't underestimate the
intellectual and research effort. More power to someone who does it!
-michael
Music synthesis for 8-bit Apple II's!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it is seriously underused."