Wither Natami?

[mikej]

"By no definition I know of (given their respective creators words on the matter if nothing else), could these two projects be called "real" amigas, since everything is being done by an emulator coded into an fpga."

It's not really an "emulator" in the sense of UAE at least, which is software running a close approximation to the original hardware on another cpu. The FPGA designs are actually copies of the original hardware.An FPGA is a big bunch of gates which have the same function as the original chips in the Amiga. The firmware wires these up to create hardware which could be identical to the original design (assuming no bugs). Electrically, in theory, you couldn't tell the difference between the original Amiga and a perfect FPGA copy - it would be the same design.

Sometimes when we design custom chips nowadays we take the source design that will be made into the chip and run it up on a really big FPGA to find any problems before we make it. The FPGA and the custom chip are the same design - ok, the FPGA is a lot more expensive and runs slower. Technology has moved forward so much since the Amiga was made we can now put all the original hardware in a modern FPGA and run it much faster and add extra features. It will be possible to run the 68000 softcore much faster than the original, how fast I don't know yet, but 50MHz plus should be no problem.

Mike.
www.fpgaarcade.com

[mikej]

"No one has the original chip designs anymore, so the FPGA Amigas are workalikes, they do not behave exactly as the original chips. "

True, but they will be much closer than a software emulation. It is possible to get exact behaviour by running the FPGA core against a real custom and looking for any differences. This is what I've been doing with the Atari chips and will do for the Amiga customs. In this way you can prove the chips behave identically to the originals for all the stuff you have tried, demos, games etc.

If somebody wants to throw money at the problem it is very possible to reverse engineer the logic by examination of a real chip - you scan the chip, strip off the metal layer and repeat. These chips are old so the feature size is large, but it's still expensive.

But, you are right, software emulation is good enough for most things.
/Mike

[mikej]

I am aware of the on-going work, and I agree UAE is accurate and configurable.
Personally I want an expandable hardware system which is accurate enough to run the software I wish to. True, the FPGA designs will be approximations to the original hardware, but with effort they can be extremely close. Logic analysis helps, but it only verifies what you capture. By running the two chips in lock step you can verify function and timing.

The Atari custom chips I have been working on are gate level accurate. (I am an ASIC designer by trade).

At the end of the day, I think expandability is more important that complete compatibility, it's sort of fun to add hardware features we all wished were there from the start. Ok, you can do this in the software emulator, but it's a bit more real when it's a small board sitting on your desk?

Best,
/Mike

[mikej]

"Forgive me, but the Atari chips were quite a bit simpler than the Amiga ones."

yes, that's why I started with them