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From: rokicki@Neon.Stanford.EDU (Tomas G. Rokicki)
Newsgroups: comp.sys.amiga
Subject: Stanley Chow
Message-ID: <1990Jan10.071333.23967@Neon.Stanford.EDU>
Date: 10 Jan 90 07:13:33 GMT
Organization: Computer Science Department, Stanford University
Lines: 53

Nice try.  You seem to have a massive misunderstanding of the
MOVE SR instruction.  This instruction moves the status register
*to* a data register.  It cannot be used to enter supervisor mode;
it can only be used to observe whether you are in supervisor mode
or not.  Thus, the 68000 only `fails' as a virtual machine when
you are running code that must (and counts on) determining whether
or not it is running supervisor or not---such code as an operating
system.  User programs should not (and do not, by and large) use
this instruction.

>  1) A machine base on the 68K family can be made to be Object Code 
>     Compatible at the User level. This means the operating system must
>     be changed/patched to handle the MOVE SR case.

True, except that 99% of the software (and certainly all productivity
software) does not use MOVE from SR, so there is no problem.

>  2) A stock Amiga equiped with a 68010 is *not* object code compatible
>     at the user level. A patch is required (the famous DeciGel).

A patch is only required to run certain brain-dead software that
does not follow the Commodore-Amiga guidelines (ie, use the system
call GetCC() to get the condition codes, rather than Move SR.)

>  3) Commodore-Amiga does not sell the needed patch. There is no offical
>     support for the patch.

Commodore Amiga has no responsibility to support software that breaks the
rules.  Any software that needs the patch has broken the rules.  Very few
packages are affected at all.

>  Therefore, "Amiga does not support the 68010".

Sorry.  Amiga supports the 68000, 68010, 68020, and 68030.

>  5) I have taken programs written for the XT written before the 
>     advent of '286 & '386 and run them on AT and 386-clones. They all
>     run with no problems (except for Video or other hardwares). In fact, 
>     the earliest versions of MS-DOS runs on all machines. Furthure, any
>     combination of {program-version, DOS-version} that runs on any 
>     machine should run on all machines.

BFD.  Most of the Amiga software written in '85 that followed the written
guidelines works like a charm, even despite radical changes in the
operating system.  On the IBM, on the other hand, programs written for the
early PC fail badly on modern PCs (mostly due to the new hierarchical file
system.)

Stanley, it really seems like you are picking a fight from a point of very
shallow knowledge.  Yes, you did read the books, but did you understand
them?  Relax a little, my man.

-tom