Are you buying an FPGA Amiga?

[alexh]

I never bought one, but I was loaned a MiniMig from ACube to help develop new cores. However they sent me one with a PIC without TinyBootloader and so I couldn't reprogram it. They said they would send a replacement PIC but never did and it has sat on the shelf in the office ever since.

[mikej]

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

[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...

[Franko]

Agreed.  While I might be running most of my games in OCS/ECS/AGA screenmodes, I couldn't life without RTG for Workbench, word processing, web surfing, etc which is probably why I tend to ignore my A1200s.

I don't see the point myself in RTG for the Amiga, to me part of the whole charm of the Amiga is getting the best out of it's limited palette and screen modes...

RTG when you look at some of the screenshots folk place on the web just make it look like a poor version of a Mac and take away that feeling that your actually using a real Amiga...

Be nice to see what the new screenmodes of the NatAmi can do but I think it's more important that if the NatAMi takes off then at least programmers will have a de-facto standard to start writing new stuff for...

[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.

[alexh]

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.

In theory yes. In practice no. But you know this

Because the original schematics & netlists of the CBM chips have been lost over time. The FPGA contents are all re-interpretations by their various authors of how the Amiga hardware worked taken from the various specifications and from observations using logic analysers etc. Lots of information was undocumented and slowly comes out over time in the form of incompatabilities.

The guts of the original MiniMig especially does not work (buses etc.) how the original Amiga worked.

[mikej]

In theory yes. In practice no. But you know this

Because the original schematics & netlists of the CBM chips have been lost over time. The FPGA contents are all re-interpretations by their various authors of how the Amiga hardware worked taken from the various specifications and from observations using logic analysers etc. Lots of information was undocumented and slowly comes out over time in the form of incompatabilities.

The guts of the original MiniMig especially does not work (buses etc.) how the original Amiga worked.

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

[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.

[Scottish_Chris]

What's an FPGA AMiGA?

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

[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.

[JimS]

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.

Both the Replay and Natami are custom boards. The original minimig used a stock Spartan 3 development board with two hand built boards for the CPU and the PIC system controller.

[Darrin]

I never bought one, but I was loaned a MiniMig from ACube to help develop new cores. However they sent me one with a PIC without TinyBootloader and so I couldn't reprogram it. They said they would send a replacement PIC but never did and it has sat on the shelf in the office ever since.

I wish you told me that.  I replaced my PIC with an ARM controller so I could have sent you mine.

[psxphill]

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

FPGA clones can be identical, if they implement the same logic as the original. However nobody has done this, the fpga replacements may function at a gate level but they aren't even conceptually the same gates as the originals had. If you could decap an agnus and then copy & paste that onto an fpga then you'd have a point, but you know it's not that easy.
 
I'm not against fpga amigas, I love the work you've done on the fpga arcade & the natami sounds really exciting (I just hope it lives up to it).
 
However I don't know how to reconcile the difference between a 15khz crt and a hdtv, even though an amiga with 1080p output would be cool. I guess this is why the natami is going for amiga compatible but no compromises when looking at what they can do to improve it. While the fpga arcade is more about the original experience, to me that means 15khz video and noisy paula output (and a filter connected to the power led).
 
For instance I prefer the 1541 Ultimate 2 to the chameleon because I can't see why anyone would want to connect a c64 to a vga monitor.

[persia]

What advantage do FPGA Amigas have over UAE Amigas?

[ChaosLord]

to me part of the whole charm of the Amiga is getting the best out of it's limited palette and screen modes...

Amiga A1200 does not have a limited palette.

Its palette is 16.7 million colors the same as your bgcPC or mac.

[Darrin]

What advantage do FPGA Amigas have over UAE Amigas?

Simplicity, and you don't have to cart around a PC for starters.

I use Amiga Forever and a Minimig.  The Minimig "feels" like my real Amigas with regards to booting, responses and that lovely ability to attach "Atari" joysticks to the ports.  One look at UAE's configuation menu is enough to put you off.