
Making a C64/C65 compatible computer in an FPGA - mmastrac
http://c65gs.blogspot.com/2017/06/building-lab-prototype-mega65-and.html
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orionblastar
Would it be cheaper to use a FPGA or just make a C64 C65 on a chip?

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klodolph
FPGA: low tooling cost, higher unit cost

ASIC: high tooling cost, lower unit cost

An FPGA conversion ASIC would be $35,000+ NRE, and that's pretty cheap. An
FPGA is what, under $100 these days? The reason ASICs are cheap is because you
sell thousands or millions of units to amortize the NRE cost.

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bsder
> An FPGA is what, under $100 these days?

More like under $20. And has enough RAM that you don't need an external RAM
chip for something like emulating a C64.

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SwellJoe
I recall reading development was being done on a pretty beefy FPGA; one that
would not be limited to emulating just the C65 (note the C65 was based on a
65CE02 16-bit CPU at ~4MHz, and not the 8-bit 6510, so quite a bit more
demanding than a 6510 at ~1MHz).

I went searching for prices way back when I first started reading about the
Mega65 project (I donated back then and got access to the core files, but
didn't go through with buying an FPGA to try them on), and I think the FPGA in
single-unit quantities was over $200. I may be misremembering, and I may have
looked at the wrong vendors, though. But, I think they're not targeting a
super low-end market for this project. Which, I think is reasonable. People
with no money to spend will run an emulator.

So, I hope it won't be _too_ expensive, but I won't flinch if it's a few
hundred dollars, even though I picked up my current working C64 for under $50.

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bsder
A Cyclone IV GX is something like $25.

And it can run a NIOS II embedded processor (which is 32-bits) at almost
200MHz.

I would be stunned if that FPGA isn't fast enough or large enough.

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SwellJoe
This is the dev board they're using (a Nexys 4 at $320):
[http://store.digilentinc.com/nexys-4-ddr-artix-7-fpga-
traine...](http://store.digilentinc.com/nexys-4-ddr-artix-7-fpga-trainer-
board-recommended-for-ece-curriculum/)

I imagine the FPGA alone, without the ancillary stuff will be somewhat cheaper
(nope, I checked...not much cheaper...DigiKey has the Xylinx Artix-7 in single
quantity for $256). I'm not an expert on these things, so maybe I'm looking at
the wrong parts.

I just recall looking up what it would cost to run it today would cost, and
thinking, "I'll just wait until they ship it all in a nice C65 style case".

Here's the discussion about the size of it: [http://mega65.net/fpga-
development-boards](http://mega65.net/fpga-development-boards)

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bsder
o_O !!!!!

Talk about overkill. Holy cow.

These guys did a 50MHz 6502 back on a Cyclone II:
[http://www.cs.columbia.edu/~sedwards/classes/2013/4840/repor...](http://www.cs.columbia.edu/~sedwards/classes/2013/4840/reports/6502.pdf)

It looks like they're going for an FPGA that has 512K+ of RAM directly on
board. That's really expensive and I note that even the Altera stuff is in the
same range of price. That's a poor design decision.

4Mb SRAMs are something like $10 with a 10nS access time.

Clearly some inexperienced hardware designers.

