ColdFusion CF4000 prototype Arrives!

[Piru]

@AmigaMance

Why does a 68k cpu has to emulate a 68k cpu?

Coldfire is not 68k CPU.

I have read that this is required for some fpu instructions only.

That's not the case.

Anyway, check out the thread about Elbox Dragon compatibility?, it has some discussion about the coldfire emulation issues. As you can see there isn't exactly full consensus about this matter, but as soon as (or if ever) some coldfire accelerator hits the market we will know for sure.

[Fransexy_]

Coldfire is not 68k CPU.

From freescale webpage:

With its architectural relationship to the 68K Family, customers using 68K products should consider a standard ColdFire product as their next solution.  Because the ColdFire processor instruction set is a subset of the 68K Family instruction set, existing 68K customers find that designing with ColdFire microprocessors is a smooth transition.

Sounds to me like a evolution of 68k CPU  :-D

And about compatibility, again from freescale webpage:

You can find tools such as an automated 68K-to-ColdFire processor converter and an emulation library available

So, i think that you only need a library for compatibility not much more different of 040 and 060 accelerators in which you need a 68040.library to work

[Fransexy_]

So, i think that you only need a library for compatibility not much more different of 040 and 060 accelerators in which you need a 68040.library to work

And not much more different of the 64 bit risc AMD chips emulating x86 cisc instructions

[Piru]

@Fransexy_

Sounds to me like a evolution of 68k CPU

Nope. It's completely new design, but it took the best aspects of m68k series (easy & logical asm programmability).

Keywords to look for: relationship, subset

It's no 68k CPU. Only later it added more m68k series compatibility, but it still is no m68k.

And about compatibility, again from freescale webpage:

You can find tools such as an automated 68K-to-ColdFire processor converter and an emulation library available

So, i think that you only need a library for compatibility not much more different of 040 and 060 accelerators in which you need a 68040.library to work

Wrong. This is automated *source-code* converter.
Emulation library allows you to run usermode code with performance hits (depends on the emulated insruction occurance rate).

And regardless, at supervisor level these CPUs are completely different. You must have full emulation or the board will not be able to run most games and demos.

Further, coldfire accelerator can't work with just something like 680x0.library. The system would never get to point where it could load the library from disk, the CPUs are too different. Basically the emulation would need to be available even before the system begins to execute the Kickstart ROM code.

[Piru]

So, i think that you only need a library for compatibility not much more different of 040 and 060 accelerators in which you need a 68040.library to work

And not much more different of the 64 bit risc AMD chips emulating x86 cisc instructions

Except that these AMD chips actually have full 32bit x86 emulation built-in, and that it is available at the moment the chip is powered up. As the x86 emulation is hardwired to the chip it doesn't involve any exceptions or performance loss. Even in 32bit x86 legacy mode these AMD chips kick serious behind.

Coldfire doesn't have such built-in emulation, and the software emulation involves slow exception traps.

[_yak_]

Piru is right but I would like to hear what Oliver Hannaford-Day, the board designer, have to say about this.

[Oli_hd]

Piru is right but I would like to hear what Oliver Hannaford-Day, the board designer, have to say about this.

You rang?

Piru is right, the Coldfire has hardware built in to trap none coldfire compatiable instructions, which it then passes to a software program (if running) which translates it in to a coldfire native version (Like what oxypatcher does for the FPU on 040/060 CPU's) and passes it back to the Coldfire which loads the new instruction inplace of the old one and then continues on with the main program, if it hits another unsupported instruction the process is repeated.
The convertion software is coldfire native and has to be running before an illegal instruction is read, which means it has to be loaded before the kickstart. (Or an AROS coldfire native kickstart needs making)

The last prototype had a flash chip on the board which was designed for this, I want to have a play with a few things so there is no flash chip on this boad, instead there is a large pin header with all the required signals so one can be added later.

It's no 68k CPU. Only later it added more m68k series compatibility, but it still is no m68k.

It is a member of the same family (Freescale just say 68K/Coldfire now) and the Coldfire CPU always had 68K instructions, but only the most common ones, later Coldfire revisions added more 68K instuctions but yes, its still not a drop in replacement, and wont ever be.

I have read that this is required for some fpu instructions only.

The FPU in the Coldfire is totally different from the 68K, Freescale dont class it as a floating point unit, just an Emac, which "does" do maths equations but is very different from a 68K FPU.
(There is a true FPU in the V4e though)

Back to the 68K issue, its basically a bite it and see. When the card is done I will have to run a lot of old and new 68K software through it, see how it reacts.
The CPU might get so bogged down emulating 68K instructions that it would be no faster than a 68060.
But even then if it worked well it would still get launced as the price is expected to be very low and the ability to add 512Meg of SD-Ram would still give it an edge. (And any Coldfire native program would run at full speed (3 times that of a 68060))

[Piru]

@Oli_hd

Indeed, as more and more m68k instructions work without emulation Coldfire gets more feasible. Personally I'm a bit pessimistic about this, but maybe it'll work just fine.

However, how are you going to handle supervisor mode? My understanding is that supervisor mode is completely different in Coldfire, and to emulate m68k supervisor fully you'd need to pretty much have some full blown emulation for it (build compatible stackframes, emulate supervisor instructions etc).

[Doobrey]

Back to the 68K issue, its basically a bite it and see.

Wouldn't it be easier to take the UAE sources and modify the 68k emulation to emulate the behaviour of the Coldfire to test compatibility and look for problems before doing it for real?
 IMHO, it's a lot easier looking through the uae logfile and debugger than trying to figure out whats going on inside a real 68k during a coldstart (been there, done that, never sent out the T-shirts)

BTW, if you load in your 68k emulation/traps before the kickstart is run, how are you gonna stop the coldstart code from resetting all traps and exception vectors?..or would you add something to make it think it was a warm reset and not a coldboot?

BTW #2, Nice board , who did you get to make it for you?

[TheMagicM]

or skip the 68k amiga emu/conversion stuff..and run the CF board w/linux  & E-UAE on a A4k.. that would rock.

[Kronos]

"Rock" at the speed of a naked A500........

[motorollin]

the Coldfire has hardware built in to trap none coldfire compatiable instructions, which it then passes to a software program (if running) which translates it in to a coldfire native version

Why can't this translation be done with hardware? Wouldn't that be quicker? It would also eliminate the need for the translation software, which would mean the card would work from cold boot.

--
moto

[Oli_hd]

Why can't this translation be done with hardware? Wouldn't that be quicker? It would also eliminate the need for the translation software, which would mean the card would work from cold boot.

Well it would need to be built into the CPU if it was in hardware.
I guess its cost more than anything, the Coldfire is such a cheap CPU and thats what its designed to be, adding the missing instructions would mean a bigger piece of silicon, which would add to the cost.

Its sad they stopped developing the 68K

[Oli_hd]

or skip the 68k amiga emu/conversion stuff..and run the CF board w/linux & E-UAE on a A4k.. that would rock.

Actually thats why there isnt a flash chip on this prototype, I do want to give Linux a try.. and AROS if Im up to porting it. (Which at the moment Im not but its something I am working on)

[fx]

linux and e-uae? then you might aswell get a pc :/

[Nautilus]

It's nice, but it's trully oldware.