68EC000 documentation and behaviour

[mihcael]

68EC000 is a type of 68000, extra detail simply omitted?

[Schoenfeld]

Originally Posted by mihcael

68EC000 is a type of 68000, extra detail simply omitted?

One little detail is omitted, and that's the E-Clock syncronization which is required for talking to the CIA chips. This feature has also been removed for all 68020 and higher processors, so it's already common knowledge how to add it into the accelerator for the Amiga. Nothing to worry about - if I would not implement this properly, the unit wouldn't start at all :-).

The 68EC000 is 100% software compatible with the NMOS version of the 68000 down to the last cycle. I'd say it's OK to refer to it as 68000, as it's only the silicon level that's different; the behaviour - even on the memory bus - is identical with the chip that has powered our A500's all these years.

Jens

[chaos]

Originally Posted by Schoenfeld

The 68EC000 is 100% software compatible with the NMOS version of the 68000 down to the last cycle. I'd say it's OK to refer to it as 68000, as it's only the silicon level that's different; the behaviour - even on the memory bus - is identical with the chip that has powered our A500's all these years.

The 68EC000 works just fine as a replacement CPU for an Amiga, (it is used on the original minimig board and no problems have been noticed until now) but it isn't completely 100% compatible with the 68000, namely the MOVE SR, <EA> and the BKPT instructions, and possibly others I don't know about. Doesn't seem to affect Amiga software at all, luckily

[Toni Wilen]

Originally Posted by chaos

The 68EC000 works just fine as a replacement CPU for an Amiga, (it is used on the original minimig board and no problems have been noticed until now) but it isn't completely 100% compatible with the 68000, namely the MOVE SR, <EA> and the BKPT instructions, and possibly others I don't know about. Doesn't seem to affect Amiga software at all, luckily

MOVE SR,EA is different? I can't see any differences vs 68000. (Not like 68010 where it is supervisor only or anything else)

[chaos]

It's supervisor only on 68EC000 too AFAIK.

[Toni Wilen]

Originally Posted by chaos

It's supervisor only on 68EC000 too AFAIK.

No, it isn't. I tested it about 2 hours ago

MOVE to SR: privilege violation, MOVE from SR: ok, MOVE to CCR: ok, MOVE from CCR: illegal instruction. Normal 68000 behavior.

[chaos]

Originally Posted by Toni Wilen

No, it isn't. I tested it about 2 hours ago

MOVE to SR: privilege violation, MOVE from SR: ok, MOVE to CCR: ok, MOVE from CCR: illegal instruction. Normal 68000 behavior.

OK, I admit I never tested it on the minimig, but then the 68k user manual is wrong, plus most of other docs I read. Will try it on the minimig, though.

[Toni Wilen]

Originally Posted by chaos

OK, I admit I never tested it on the minimig, but then the 68k user manual is wrong, plus most of other docs I read. Will try it on the minimig, though.

Strange and interesting..

Same documentation also does not mention 68EC000 in MOVE from CCR.

Also "EC000 Core Processor (SCM68000) User’s Manual" documention from Motorola (1995) lists only MOVE to SR requiring supervisor mode.

(I guess this 68EC000 documentation/behavior discussion should be moved from this thread?)

[prowler]

Originally Posted by Toni Wilen

I guess this 68EC000 documentation/behavior discussion should be moved from this thread?

Done.

[Photon]

Yes, I've never heard of any difference between 68000 and 68EC000 either. I've no idea why they used the same naming convention as where the CPUs are real "lite" versions. Maybe some silly marketing thing.

And I know Motorola manuals over the years to be "almost" perfect Check the errata for any manuals in question.