Are you buying an FPGA Amiga?

[TheGoose]

I think I will, I just don't know which. I sure hope the programming of the custom chips is done well. I would think the "feel" should be a few steps beyond the pure software emulation, likes of WinUAE / Colanto AF.

The Minimig turned out really good, yes (don't have one)? Any lessons learned from that?

[TheGoose]

There have been some comments on here about
"hardware emulation not feeling the same"

Not true. In theory, the FPGA clones are "identical" at a hardware level from the originals - they function at a gate level in exactly the same way as the original chips. Well, bugs apart of course.

/MikeJ

Right, "they function at a gate level" - I think a lot of us still could use a boot camp course in what a FPGA is / does. My instinct is to view an FPGA as a super advanced EPROM. What is a good site to read up FPGA, and please don't give me the Google bit. You all start sounding like that Star Trek episode; machine do all, machine provide everything...

[TheGoose]

So I understand the AGA FPGA Replay board is built upon a Spartan FPGA board. So what is Natami made from? Is it completely homebrew? Or built upon something? I don't get that.

[TheGoose]

Thanks Alex, I was hoping you would jump in!
Alex and I both work in ASIC design, by the way.

I am in a bar in China, so if this doesn't make any sense, sorry.

Alex, forgive the simplifications here...
The original custom chips (including CPU) are made of a whole bunch of logic gates which together give the functionality of the original hardware. An FPGA is a soft chip, meaning it has a lot of gates which can be configured by a downloaded file. So, it can behave as any sort of chip if you know at a very low level how it works.

Today we use "high" level languages, such as VHDL or Verilog to write the design. This is not software, it is a description of how the circuit should look - like a circuit diagram. The design tools take this code and build a file which when loaded into the FPGA makes the circuit you describe.

If you know exactly how the original chips were designed, you can make a perfect copy.. well, for most cases of perfect.


For the Atari chips, and some CPUs we have scans of the chips which means we can re-create the exact same logic.
http://www.visual6502.org is a good example.

However, often we simplify things because the original chips were constrained by the pins on the devices, so they split the design between a number of chips. We don't need to do this, and we can make some other simplifications.

So, an FPGA Amiga in an ideal world contains the same circuit as the original, has the same bugs, same timing etc.


Yes, the Replay board uses a Spartan3e FPGA. This is a low end device (hence the low cost of the board) but is still capable of running at clock speeds of 200MHz plus inside if the design is optimised for the architecture.


/MikeJ

Damn Mike, that was pretty good for coming from a bar in China, very helpful!

So, in some places, we may be lacking information about a chip, a design. But say a year / two down the road we (community) get some new data, info is released for whatever reason; you know where I'm going with this... Can we update / fix our FPGA implementation ("field programmable" part would suggest yes...) But maybe not for most.

[TheGoose]

What's an FPGA AMiGA?

Sorry...I've been out-of-the-loop for the past 11 years.

Welcome back Chris, well that's sorta what were talking about, what is it? But for you to get a footing, I'd read upon what the Minimig is all about. Wikipedia minimig...

In short, it's very cool.