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Author Topic: Elbox Dragon compatibility?  (Read 5522 times)

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Offline motorollinTopic starter

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Elbox Dragon compatibility?
« on: May 10, 2006, 10:15:20 AM »
I'm really excited about the possibilities of the Elbox Dragon Coldfire upgrade. Does anyone know how compatible it should be with 68k software? Will I still be able to play WHDLoad games, emulate a Mac etc? Will 68k software run natively on the Coldfire, or is there some translation or recompiling required?

Thanks

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moto
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Offline CLS2086

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Re: Elbox Dragon compatibility?
« Reply #1 on: May 10, 2006, 10:29:09 AM »
Hi,
yes and add an another question, as the coldfire is partialy an FPGA, how long will it live ?  :rtfm:
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Offline Marco

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Re: Elbox Dragon compatibility?
« Reply #2 on: May 10, 2006, 10:34:19 AM »
I would imagine there'll be significant compatibility problems, I mean I have trouble getting WHDLoad games to run on an 060, I can only imagine that the Coldfire (isn't it the MCF5475 being used?) will be even worse.

I'm not too knowledgeable but I understand that the problem is that with each generation of the chip, old instructions are removed, so the 060 has some instructions missing that old games and software for the Amiga might try and access, the Coldfire, being mainly intended for embedded apps, will have an even more drastically cut down instruction set, meaning (if I have been reading this stuff correctly) even less compatability with certain apps.

TBH I'm not too interested in the Coldfire board for 2 reasons: 1. it HAS to use the Dragon PCI busboard meaning it needs a towered system and 2. we should be trying to change over completely to PPC only, like the Powervixxen boards (which would/should fit in the 1200 desktop) another vapourware product at the moment but then everything is with Amiga these days.
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Offline Piru

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Re: Elbox Dragon compatibility?
« Reply #3 on: May 10, 2006, 10:51:51 AM »
Quote
Will I still be able to play WHDLoad games, emulate a Mac etc?

As coldfire supervisor mode is completely different from m68k one, I doubt WHDLoad will run at all.

It depends on how the emulation works, really. If the thing runs full CPU emulation all the time (user and supervisor mode) then it would work. This would be crawling slow though. MMU emulation is not possible anyway (with sensible performance levels), so this rules out Mac emulators.

Until Elbox actually shows the thing running anything I'll consider Dragon vapor (no, just seeing some pics of the HW isn't enough, see SharkPPC).

Quote
Will 68k software run natively on the Coldfire, or is there some translation or recompiling required?

They will not run out of the box, emulation is involved, see coldfire-v4-m68k.txt.

There are also some other more serious differences. IIRC for example division overflow flag is not set on coldfire CPUs. This will break applications depending on this, unless if there is some full CPU emulation.
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Offline motorollinTopic starter

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Re: Elbox Dragon compatibility?
« Reply #4 on: May 10, 2006, 11:13:33 AM »
Damn, I thought it was supposed to be backwards compatible so 68k code would run at 266MHz. I'm not interested in PPC as everything I want to run requires 68k. I thought the Dragon was a super-fast 68k compatible processor. Seems I was wrong :-(

If 68k code won't run properly, then what's the point?  :-?

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Offline Piru

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Re: Elbox Dragon compatibility?
« Reply #5 on: May 10, 2006, 11:19:41 AM »
As usual elbox markets it as 266MHz 68k accelerator, which it is not. Surely it might be fast in some cases when executing specific optimum-case test-loops or such, and it might deliver this "266 MHz". However, in generic 68k emulation this is not the best CPU.

If you only use 68k, better use WinUAE. On any decent x86 system it runs circles around this ColdFire accelerator anyway.
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Offline motorollinTopic starter

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Re: Elbox Dragon compatibility?
« Reply #6 on: May 10, 2006, 11:21:07 AM »
I'm sure WinUAE would provide better performance than my 060, but I want the real thing :-)

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Offline keropi

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Re: Elbox Dragon compatibility?
« Reply #7 on: May 10, 2006, 12:10:04 PM »
so the power vixxen will still have the same prob... so what's the point really???? they just use the amiga user-base to introduce a different plattform?
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Offline MrZammler

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Re: Elbox Dragon compatibility?
« Reply #8 on: May 10, 2006, 12:43:53 PM »
@keropi

Dont confuse those two (PV and CF). As it stands now, there is a NG path for the Amiga (PPC - good or bad, that's another story). The PV aims to the NG path, the CF wants to bring the halted 68k state a bit forward.

IMHO, the CF is nothing more than an expensive with limited usage tool. Seeing from the other's reply's it wont be 100% 68k compatible, which means that at least myself would be hesitant to pu into my A3000 (yes, I do need my dose of whdload). Would I need it inside my A3000? Dont know really. It'd be cool to have a 266Mhz classic Amiga, but if it wont let me run all my 68k software, then it's of no use.

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Offline motorollinTopic starter

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Re: Elbox Dragon compatibility?
« Reply #9 on: May 10, 2006, 01:36:03 PM »
Quote
MrZammler wrote:
It'd be cool to have a 266Mhz classic Amiga, but if it wont let me run all my 68k software, then it's of no use.

My thoughts exactly. We need Dennis to create a brand new processor which contains all of the instructions of a 68k processor, but running much, much faster :-)

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Offline keropi

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Re: Elbox Dragon compatibility?
« Reply #10 on: May 10, 2006, 01:43:11 PM »
or make an emulator, put it in a rom or something and let the host cpu always "run" this emulator... could it be done?
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Offline motorollinTopic starter

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Re: Elbox Dragon compatibility?
« Reply #11 on: May 10, 2006, 01:49:20 PM »
A1200 + Elbox Dragon + MiniMig on PCI card = Ultimate Amiga  :-D

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Offline MrZammler

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Re: Elbox Dragon compatibility?
« Reply #12 on: May 10, 2006, 01:54:21 PM »
Quote

motorollin wrote:
A1200 + Elbox Dragon + MiniMig on PCI card = Ultimate Amiga  :-D


Add a PV in that and we're in business.  :-D
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Offline AmiDog

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Re: Elbox Dragon compatibility?
« Reply #13 on: May 11, 2006, 05:52:36 AM »
Quote
They will not run out of the box, emulation is involved, see coldfire-v4-m68k.txt.

There are also some other more serious differences. IIRC for example division overflow flag is not set on coldfire CPUs. This will break applications depending on this, unless if there is some full CPU emulation.


I just found this site about porting 680x0 code to ColdFire. There's an 680x0 emulation library there as well. And as you said, there are a few situation which can't be handled easily (from the FAQ):

Quote
* MULU and MULS instructions executed on ColdFire do not set the overflow flag. Because these are legal ColdFire instructions, with the same opcodes as the 680x0 equivalents, no exception is generated and the CF68KLib handler will therefore not be called. If the original code depends on multiply setting the overflow flag, it will need to be patched or modified to run correctly.

* Certain variants of the divide instructions DIVS.L and DIVU.L behave differently under ColdFire.

* MOVE.B ,-(A7) and MOVE.B (A7)+, change the stack pointer by one byte on ColdFire instead of 2 bytes as on the 680x0.

* An instruction such as MOVE.L (A7)+,(A0,D0.W) is not legal in ColdFire because word-length displacements are not supported. Although the ColdFire processor will take an exception for this instruction, it does so only after incrementing the stack pointer, and so the exception stack frame overwrites the data to be restored. As a result, it is impossible for CF68KLib to reproduce the correct behavior.
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Offline motorollinTopic starter

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Re: Elbox Dragon compatibility?
« Reply #14 on: May 11, 2006, 06:48:08 AM »
I wonder how feasible it would be to patch these functions? And what kind of performance could we expect?

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10  IT\'S THE FINAL COUNTDOWN
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60  NA-NA-NAAAA
70  NA-NA NA-NA-NA-NA-NAAAA NAAA-NAAAAAAAAAAA
80  GOTO 10
 
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