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Re: Is it possible to build a modern Apple][?
adric22@yahoo.com wrote:
This has been done with the C64 and the Vic20. The Commodore DTV sells
for under $20 and has 2 MB of RAM, 2 MB of Flash, and the main ASIC
(total of 3 chips). However, it still runs at 1 Mhz (out of need for
compatibility) but can be set to burst mode (where it takes advantage
of the SDRAM and other timing enhancements) to get approx. 4 times
faster speed, while still running at 1 Mhz.
I have a website on it:
http://galaxy22.dyndns.org/misc/hummerdtv/index.html
One other note.. it isn't neccessary for the device to run at 5 ghz
just to be 5000 times faster. Old 8-bit systems are very inefficient
use of bus cycles, amongst other things. I would imagine you could
easily be 5000 times faster just using 200 to 300 Mhz.
Actually, the 6502 design is very efficient in its use of cycles,
and is one of the first pipelined microprocessors.
But the design is predicated on an intimate, cycle-by-cycle coupling
to memory--not at all like modern processors. And programs written
for the 6502 are often strongly dependent on the precise timing and
bus activity that they generate.
As a result, an emulation of a 6502 on a modern processor is likely
to be about as good as building one directly--unless you toss out
all the "lockstep" characteristics of the 6502 that many programs
exploited.
But back to the original question.. I too am interested to know the
answer (not using an FPGA) I investigated this question for the
Commodore systems about a year ago. I had a quest to build one from
off-the-shelf parts. Unfortunatly there are no substitutes for the
sound and graphics chips in the commodore systems. (without going to a
custom ASIC or FPGA) I think I determined that one could, in fact,
build a Commodore PET from off-the-shelf parts. (but who would want
one?) But I do not know enough about the Apple II systems to know if
there are chips that can't be substituted.
You can still build an Apple ][ from TTL and a 65C02, so that's not
a problem. Higher levels of integration could be a problem if the
design is not partitioned properly. Of course, it all fits into one
FPGA these days, so there really isn't any problem... ;-)
-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."