[comp.sys.amiga.emulations] re : Transformer - IBeM for 68000s RSN !

chem194@csc.canterbury.ac.nz (John Davis) (04/29/91)

In article <Yc6=yR600WB7MKL1tS@andrew.cmu.edu>, ia0i+@andrew.cmu.edu (Indu Tara Agarwal) writes:
> Hi,
> 
> I recently went to all the trouble of downloading IBeM from ab20, only to find
> out that the program (which everyone seems to praise) doesn't run on 68000
> machines.  So I guess I need the "Transformer".  What I would like to know is

Hang in there, Mark Tomlinson who wrote IBeM is currently working on
an upgrade that will allow IBeM to work on ANY model Amiga with
ANY amount of memory. On a 68000 it'll be just as slow as transformer
used to be (Norton SI rating of .1) but it will at least work reliably
(Transformer seemed to have real problems with KS1.3/1mb chip etc) and
more importantly multi-task (Transformer took the system over) and 
support hard-disk partitions...

Now if only Mark would stop bug-hunting for long enough to read
this group and reply himself... :-)

-----------------------------------------------------------
| o  John Davis - CHEM194@canterbury.ac.nz               o |
| o  (Depart)mental Programmer,Chemistry Department      o |
| o  University of Canterbury, Christchurch, New Zealand o | 

psteffn@pogo.gnu.ai.mit.edu (Paul Steffen) (04/29/91)

Wouldn't it be possible to do some exception handling so that you could
emulate the extra '20/'30 opcodes on a '00?  It seems feasible
to me but I haven't seen anyone do it yet.  Perhaps this should

go to the 68k newsgroup.  

tomlin@cosc.canterbury.ac.nz (M. Tomlinson) (04/30/91)

In article <15380@life.ai.mit.edu> psteffn@pogo.gnu.ai.mit.edu (Paul Steffen) writes:
>
>Wouldn't it be possible to do some exception handling so that you could
>emulate the extra '20/'30 opcodes on a '00?  It seems feasible
>to me but I haven't seen anyone do it yet.  Perhaps this should
>
>go to the 68k newsgroup.  

Unfortunately this can't be done.  The new instructions can be done this
way by trapping the illegal instruction vector.  But the new addressing
modes can't always be trapped.  For example
     move.w   0(a6,d3.w*2),d0
is not valid under the 68000 (because of the *2) but is valid on 020's/030's.
I had a program that used this instruction and it did not cause any trap
or guru when it encountered this instruction.
The same was true for a lea $10000(a3),a2 instruction (offset too large for
68000's) and still no trap!
Another problem is reading words/longs at odd addresses.  Most 68020 code
doesn't do this, but this too would be tricky to do on the 68000.

(This does sound like the right group for this - its emulation of 68020
processors on the Amiga!).

 - Mark Tomlinson