FPGA Replay Board

[Mathias]

Hi,I am the one who is coordinating the Atari Coldfire Project (reloaded) for more than 2 years now.

On the Natami forums, the Atari Firebee team are keen on using Natami as a future Atari platform as well.  They aren't completely happy with the Firebee hardware in the long run...it seems.

That was not what I said. There are some users who are not 100% happy about the choosen Coldfire. This dicussion "PPC or ColdFire or emulation or something else" is as old in Atari scene, as Motorola abandoned the further development of the 060. ;)So what I meant at Natami, is that some Atari users think the way of the self made 070 is interresting. And maybe there will be a future for some cooperation (like viceversa some Amiga users contacted us and asked for Amiga possibilities at the FireBee, what also could be done, but not by us). But of course noone inside the Atari Coldfire team thought about simply using a Natami as Atari. And remember Atari scene is in the glad situation, to have the Suska board as well - deliverable for nearly 2 years now.

But that could just be a vocal minority.  The time for competition is at an end.  Co-operation is the future, imho.

Yes, exactly. And if there is any chance for cooperation, we try to do so. But we are in a better situation as we have the sources of TOS (Atari TOS & EmuTOS) and MiNT, what makes it possible at all to use a coldfire processor.

[Mathias]

Well the Firebee is based on a 266Mhz Coldfire cpu.  So an '060 based system feels like going backwards for them since they'd still be limited to ~100Mhz.  They also want a roadmap forward and not just replacing failing classic hardware with modestly improved new hardware.

You are right. And as we as community would not be able to do such a big switch to PPC, we try to make Atari applications usable at ColdFire CPUs. We have that AHCC compiler that can do binaries that are working on 68020 up to including Coldfire processors. So the plan is to have a new hardware and new applications that will work on the existing "high end" Ataris like CT6x or Hades/Milan as well as at the FireBee.

[Mathias]

Neat!  How did you get the sources?

Both Madusa as Milan are involved at the Atari Coldfire Project. And both bought licences for their computers mid of the 90ies. The contracts were done with the original Atari Inc. before it was sold to JTS in 1996. So we have the original TOS sources, not disassembled code.

[Mathias]

While you are here, can I ask you a question about the Firebee?

Of course!

Specifically, how do you handle running old 68k binaries with no source available

I am not a developer, so I doubt I can give you a real satisfying answer. But let´s try; there is - inside our Basis-System – a usermode, supervisormode, and a real hidden supervisormode. This 3rd new mode is unaccessable by the Operating System, and with heavy usage of MMU and illegal instructions handler most applications will work.

that use instructions that exist on both the Coldfire and 68k CPUs, but behave differently on each?

Especially that issue is unsolved recently. We got cf68klib implemented inside the OS, but that few instructions are not done. But as I understood Atari applications make very few usage about them. I have to discuss it again with our OS-gurus, but I belive there are 2 instructions (?) that behave different. There are some ideas/concepts, but work on it will start this summer, as we also plan to do our own 68k handler, once the first series is out to the customers.

[Mathias]

An idea for you guys: Look into a tracing JIT.

Something like this is planned by Fredi Aschwanden. I just avoided the word JIT, because I do not completely understand it myselve, and the next question normally is "why not us a PPC than" ;)Such a "partial JIT" will solve everything except selfmodifying code as far as I understood. I will post your message insiode our development forum. Thanks.

[Mathias]

Well, you could just as well ask "why not switch to emulation",

Hahaha, belive me it was asked several (!) times, as we got the real good VM Aranym!

but then I guess most of us here aren't all that rational when it comes to our attachment to the M68k architecture

Well, it seems the Amiga crowd is as crazy as we are Thats exactly the point a dedicated hardware is something completely different.

 
And the other thing is that a JIT from M68k to PPC is massively more complicated. A M68k to Coldfire JIT can just skip past most instructions, and so for almost all instructions all it needs to know is how to determine that they fall in the "safe/compatible" category, and how to figure out the length of the operands to skip them. For m68k that's very easy for most instructions - there aren't that many variations of the encoding.  

Exactly! Please spread that informations I had huge problems and was tortured whith the question "why beating a CF to compatibility with 68k". And it was really hard to understand for some people that a CF is much more easy, and that the Atari community is not strong enough any more to get a processor swichth done. Also many people didn´t get the fact that we can produce binaries that run on CF AND 68k. the AHCC compiler/assembler is already able to do so for one year now.

In theory

Well in theory we could even boot a 8-bit machine or a Amiga 500 natively at the FireBee. But it needs to be done by anyone, … It´s always the question of reasonable amount of work compared to the aim. aNd in case of an Amiga, I always said there is no sense as you have the Minimig and soon the X1000 as Natami. For the rest of your posting, volutneers are highly welcome at every time )

[Mathias]

See, the thing is I'm very tempted to write a tracer for M68k, but I've overcommitted myself to way too many projects already that are all proceeding at snails pace, so I'm hoping to trick someone else into doing the work :-P

Well thats a very cool plan, even extremely tricky . I like it Just let´s talk more about it, maybe some volunteer will show up.

The Coldfire part isn't really *that* interesting for me (though it'd be kind of cool to get AROS M68k running on Firebee...), because it's not that relevant for Amiga,

Maybe if we tell people as well, that there would even be the whole thankfulness of Dragon- and Coldfusion-team belonging to this volunteer as those two projects could be produced in series afterwards, ... ;-P

but there's tons of other cool stuff you could do if someone wrote a generic M68k tracer (e.g. one that's configurable as to which instructions it traps), like building all kinds of funky debugging and analysis tools that'd work even on non-MMU systems.

Thats also a nice idea I didn´t think about.