AROS68K and the Freescale Coldfire CPU

[WolfToTheMoon]

I've been following the Atari Firebee(Coldfire) project with great interest.

They seem to be close to delivering their promised product(for 599 euros which includes the 120 euros for the FPGA onboard which we would not need if the AGA would be used for legacy apps). The hardware phase is mostly over and now they're primarily busy with porting software.
As far as I can see, they have successfully managed to overcome the Coldfire 68K incompatibility with something they claim to be a "light compatibility layer".

Since AROS68K is open source(the Atari team has done some patching of the TOS source code). I'm no expert here and I'd be interested in some of the more knowledgeable members opinion, but I believe a similar process could be possible to enable full Coldfire compatibility for the AROS68K.

Why am I bringing this up? Well, the Coldfire v4 offers DDR RAM, has MMU, FPU and clocks at 266 MHZ(400 MIPS). It is also cheaper then 68060 and runs with very little power(3-5 W). For those not being able to buy what is probably going to be a very expensive NATAMI board, it might be a viable alternative to get significantly more performance out of AROS68K and their 68K systems. The Firebee can now run FireTOS at 1920x1080 resolution!!!

http://acp.atari.org/

[Piru]

It still won't run amiga 68k software so I don't see the point. Why not just use x86?

[psxphill]

Since AROS68K is open source(the Atari team has done some patching of the TOS source code). I'm no expert here and I'd be interested in some of the more knowledgeable members opinion, but I believe a similar process could be possible to enable full Coldfire compatibility for the AROS68K.

It's perfectly possible to run aros on coldfire. The question is whether it's actually worth it.
 
Compatibility for old applications is a problem. You'd need to either to create patches or come up with a dynamic recompiler that converts 68k to coldfire at run time.
 
For the price there are more powerful solutions.

[WolfToTheMoon]

It still won't run amiga 68k software so I don't see the point. Why not just use x86?

I agree, use x86. I'm simply asking whether it'd be possible to do a Amiga "FireBee" edition for the 68K guys. The Atari crew seem to be able to work with it just fine. Sure, you'd need to recompile apps to run on AROS68K coldfire, but at least it offers a significant performance upgrade for a decent amount of money.

One solution might be maybe to use the onboard 68K for legacy software and Coldfire board for AROS68K.

[matthey]

There are plenty of threads on this forum as well as the Natami forum about why ColdFire is less than optimum for the Amiga. AROS 68k probably will be part of the future for some fpga based 68k Amiga though. That is what the Natami is planning...

http://www.natami.net/

[WolfToTheMoon]

There are plenty of threads on this forum as well as the Natami forum about why ColdFire is less than optimum for the Amiga. AROS 68k probably will be part of the future for some fpga based 68k Amiga though. That is what the Natami is planning...

http://www.natami.net/

Yes, I'm well aware of the Natami and their plans. The problem with Natami is price. It will probably be expensive.
Coldfire less then optimum for the Amiga? I agree it's less then optimum for the KS/WB 3.1 combo for known issues. However, not for AROS68K, since it could be patched to remedy any issues with compatibility. The issue remains for the legacy 68K software, but that could be handled by the 68K/AGA on board A1200/A4000.

Looking at the Atari Firebee project, I think one could get a expansion board with the Coldfire CPU with similar power for lower price then Natami. It would lack Natami-specific features like Super-AGA, but it could also pack it's own graphics system that could be more powerful then Natami's if not AGA related.

[Piru]

The issue remains for the legacy 68K software, but that could be handled by the 68K/AGA on board A1200/A4000.

No I couldn't. There's no way the coldfire board and the on board 68k could do proper cache snooping, leading to the same issues that existed with the powerup boards: Cacheflushes on context switches.

Unless of course you mean rebooting to 68k AmigaOS to run amiga apps of course...

[Karlos]

Bus snooping was supposed to be a feature of the 68040 and above when working in environments with DMA controllers and such, but did it ever actually work?

[matthey]

Looking at the Atari Firebee project, I think one could get a expansion board with the Coldfire CPU with similar power for lower price then Natami. It would lack Natami-specific features like Super-AGA, but it could also pack it's own graphics system that could be more powerful then Natami's if not AGA related.

 Don't just look at clock speed of the ColdFire vs N68k vs 68060. The ColdFire is a cut down "cheapened" 68k CPU for embedded systems. It's not as powerful as the 68060. Sure, it has larger caches and some modern features that the 68060 didn't get way back then but adding those would have been easy had the 68060 been continued. Motorola/FreeScale didn't want the 68k/ColdFire competing with PowerPC. There is no future for ColdFire except as a little brother "embedded" CPU. The N68k project is an attempt to continue the 68k line as a powerful processor. The 68k was abandoned because of marketing reasons before it's power was explored. The N68050 should already be on par with the V4 ColdFire at a lower clock speed while the N68070 should easily outperform it. Parallel processing is a big part of the reason why. The N68k should be much easier to program and much more Amiga compatible than the ColdFire too. If you want a cheaper Amiga than the Natami, then there is the MiniMig 68020+AGA. I'd rather go that route than try and make a cheap ColdFire based Amiga.

[WolfToTheMoon]

Don't just look at clock speed of the ColdFire vs N68k vs 68060. The ColdFire is a cut down "cheapened" 68k CPU for embedded systems. It's not as powerful as the 68060. Sure, it has larger caches and some modern features that the 68060 didn't get way back then but adding those would have been easy had the 68060 been continued. Motorola/FreeScale didn't want the 68k/ColdFire competing with PowerPC. There is no future for ColdFire except as a little brother "embedded" CPU. The N68k project is an attempt to continue the 68k line as a powerful processor. The 68k was abandoned because of marketing reasons before it's power was explored. The N68050 should already be on par with the V4 ColdFire at a lower clock speed while the N68070 should easily outperform it. Parallel processing is a big part of the reason why. The N68k should be much easier to program and much more Amiga compatible than the ColdFire too. If you want a cheaper Amiga than the Natami, then there is the MiniMig 68020+AGA. I'd rather go that route than try and make a cheap ColdFire based Amiga.

The 68060 does 110 MIPS @ 75 MHz
The Coldfire V4(e) does 400 MIPS @ 266 MHz

The advantages of the 68060 is that it is a fully superscalar design, while the CF V4 is only partially so. Still, your reasoning may apply to lower end V1, V2 and V3 Coldfires. I believe a CF V4(e)  @ 266 MHz is handily faster then any 68K silicon. The V5 Coldfire is fully superscalar(and 300 MHz) but Freescale will only make it for you if you order a (pretty) large number of them.

The N68050 should already be on par with the V4 ColdFire at a lower clock speed while the N68070 should easily outperform it

the key word being "should"

[B00tDisk]

I recall reports of Elbox's "Dragon" which ran @266mhz effectively being about the speed of a 40mhz 68040 in real-world tests due to compatibility trapping, etc.

IOW, coldfire ain't gonna happen for the Amiga.

Not at a speed that makes any sense.

Frankly what I'd like to see is something like taking a single-core Atom or Geode and running a virtualized 68k CPU with JIT on it on an Amiga accelerator card.  Although I'd wager interfacing a virtual CPU to real hardware in that circumstance would be a nightmare to attempt.

[WolfToTheMoon]

I recall reports of Elbox's "Dragon" which ran @266mhz effectively being about the speed of a 40mhz 68040 in real-world tests due to compatibility trapping, etc.

That's known for the AmigaOS and I'm not suggesting that.

But here we're talking about AROS68K. Which could be patched to avoid compatibility trapping on ColdFire. The only thing in question is how to provide full backwards compatibility with 68K... software or hardware emulation?


P.S. The V5 Coldfire @ 333 MHZ does 610 MIPS.

P.P.S. If what you say is true that it would be about 40 MHz 68040 in "emulated" mode, than maybe that's not that bad after all. Which memory and bus speed did Elbox's Dragon run? I'm thinking DDR2 RAM should speed up things. ATA controller is also built in V4e core.

[matthey]

The 68060 does 110 MIPS @ 75 MHz
The Coldfire V4(e) does 400 MIPS @ 266 MHz

The advantages of the 68060 is that it is a fully superscalar design, while the CF V4 is only partially so. Still, your reasoning may apply to lower end V1, V2 and V3 Coldfires. I believe a CF V4(e)  @ 266 MHz is handily faster then any 68K silicon. The V5 Coldfire is fully superscalar(and 300 MHz) but Freescale will only make it for you if you order a (pretty) large number of them.

The 68060 is already about the same MIPS/MHz as the V4 ColdFire with smaller caches, no link stack, etc. The 68060 can do more per cycle than the V4 ColdFire. Multilplication, division, shifting is all faster on the 68060. The 68060 has useful instructions that are missing on the ColdFire. Granted, the ColdFire has some useful instruction additions also. The N68k has everything except clock speed. None of the instructions are missing, ColdFire additions are included, other instruction additions are useful, multiple instructions per clock are possible, large caches, link stack, predicated branches, byte and word instructions are as fast as long, bitfield instructions are fast, large instruction prefetch, etc. The V4 ColdFire is nothing special. It's on par with a very fast 68040 with larger caches and a few other enhancements. The V5 ColdFire is a different story. It's more like a 68060 from what little information I could find on it. It would very likely be faster than the N68070 will be in fpga. The ColdFire does need optimized code and would be harder to get max performance from than the N68070 as currently planned. It's easy enough to say, just compile new code for it, but that's where a lot of the problem is. Compilers generate poor code especially on the 68k. I have a library that started out at 67648 bytes and I have optimized down to 39824 bytes so far. I think 1/2 the original size is possible although I'm optimizing for speed and not size. Before you say that this must have been some poor C coders, I'll tell you that this piece of work was done by a fairly famous pair of brothers (in Amiga land) who now work for Hyperion. I hope there PPC optimizing is better because the PPC is not nearly as forgiving of crap code.

[Iggy]

That's known for the AmigaOS and I'm not suggesting that.

But here we're talking about AROS68K. Which could be patched to avoid compatibility trapping on ColdFire. The only thing in question is how to provide full backwards compatibility with 68K... software or hardware emulation?


P.S. The V5 Coldfire @ 333 MHZ does 610 MIPS.

P.P.S. If what you say is true that it would be about 40 MHz 68040 in "emulated" mode, than maybe that's not that bad after all. Which memory and bus speed did Elbox's Dragon run? I'm thinking DDR2 RAM should speed up things. ATA controller is also built in V4e core.

Re-werite an OS that hasn't been finished yet to run on a CPU thats only partially compatible. Then require that apps be re-compiled for the new CPU or run in an emulation mode that provides much lower performance. The entire idea sounds kind of painful.
And how are you going to implement the rest of the chipset?  Is this going to be an accelerator card or a complete new computer?

Yes the Natami will be fairly expensive, but hopfully it will offer a good level of compatibility. Your idea doesn't offer much compatibility at all.
Personally, I'll stick with NG OS' and hope for better emulation as they progress.

[WolfToTheMoon]

Re-werite an OS that hasn't been finished yet to run on a CPU thats only partially compatible.

I think "re-write" might be just a tad bit too extreme. Sure, some patching would be required. I plan to maybe get an ColdFire evaluation board  once AROS68K progresses enough and test it.

Then require that apps be re-compiled for the new CPU or run in an emulation mode that provides much lower performance. The entire idea sounds kind of painful.

The way you say it it does sound painful.
But I'd like to investigate further just how much is the performance drop of using Coldfire with AROS68K and then see whether it is painful or not.

And how are you going to implement the rest of the chipset?  Is this going to be an accelerator card or a complete new computer?

It makes sense to be an accelerator card since it would be much cheaper to the end user and I would consider this to be a hobby and the lower the price the better(Also, then I'd avoid having a FPGA aboard which is expensive).

Yes the Natami will be fairly expensive, but hopefully it will offer a good level of compatibility. Your idea doesn't offer much compatibility at all.

Too early to say about compatibility. But if I can get 68040 performance of the CPU in the emulation mode, I'd be more then happy. The rest of the board should be pretty powerful(compared to classic 68K systems).

Personally, I'll stick with NG OS' and hope for better emulation as they progress.

I agree to that. I hope to develop for the future WB X(which will have emulation). This would be a fun side hobby project and it might benefit those people who'd like to keep their 68K hardware(and benefit me to gain more knowledge on the matter). I'm still undecided whether to go with something 6502-based or 68k based. Might end-up doing an 16-bit C64 clone afterall . It would be cheaper and simpler. But if I can get people interested in this, then maybe a joint effort could be made. I'll talk with some of the local Amiga users and see if anyone is interested.

It would not be a commercial project since I cannot guarantee to be able to finish it, whatever the reason. :roflmao: