Amiga Quiz

Ethan Dicks ethan.dicks at gmail.com
Wed Nov 22 04:48:16 CST 2006


On 11/22/06, Chris M <chrism3667 at yahoo.com> wrote:
> > The original A4000 was a 68020 wasn't it?
>
>  Apparently an '030.

Yep... a 68EC030, to be specific (no MMU, thus Enforcer won't run, etc).

One _can_ replace the 'EC030 with a full 68030, but a full-on SMT
rework station is recommended.

It's easier to upgrade the CPU board to an 040 or better.

>  I remember reading an article that the 68010 was more
> or less a drop in replacement for the 68k in the
> Ataris.

The Amiga, too.  The difference is that the "MOVcc" instructions are
priv'ed on the 68010, and the stack frame can be larger, permitting
true instruction restart, and, thus, easy-to-implement page-demand
virtual memory, a-la UNIX.

One "test" for the 68010 in the Amiga is to run OS1.1 (if possible),
then fire up the calculator.  You should get a Guru Meditation with a
68010 installed and not a 68000... it's an embedded MOVcc in the
application (rather than a call to the OS which _does_ know what to
to).  The Calculator app that comes with OS1.2 does request the
condition codes from the OS rather than executing a potentially
illegal instruction in user mode.

> My AT & T 7300 UNIX Peecee has a 68010.

Yep... it needs that for its virtual memory implementation.  It's
_possible_ to design a true 68000 system with VM, but much, much
harder, typically requiring external state-saving hardware or, as in
the case of the Perkin-Elmer workstation, a second 68000 to take care
of things while the primary CPU is page faulting.

>  Seems the '020 is still available from Digi-Key, but
> it ain't cheap.

Anyone that still carries any of the older CPUs new is likely to have
a price that seems painful.  OTOH, how many places _still_ carry the
'020?  You are paying for storage and inventory, not the chip itself.

>  Not likely, but did anyone produce a processor
> upgrade for the Lisa/MacXL?

No idea.

-ethan



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