🚀 go-pugleaf

In <4395hf$89n@feenix.metronet.com>, dcorn@metronet.com (David Corn) writes:
>pvdh@motship.xs4all.nl (Paul van der Heu) wrote:

>>AmigaOS has been 32bit since 1985

>I'm aware Dave H. has said that, but can you run your 68040 in
>Workbench 1.0, 1.1, 1.2, or 1.3 with the copyback cache on?  

The AmigaOS didn't fully support the 68040 until AmigaOS 2.04.

>How do you define 32-bit?  

Flat-model addressing and 32-bit A/D registers and instructions in
user mode programs. 

>Do you define it as using 32-bit instructions?  As being able to run
>32-bit compiled programs especially for the 020 and above?  

Those things don't somehow add to the "32-bit-ness" of the OS. I don't
know how PowerPC handles it, but on the 680x0, there's a clear
division between user and supervisor modes. The Amiga's microkernel
(Exec) partially in supervisor mode, most everything else runs in user
mode. There are certain aspects of the 68040 that required additional
supervisor mode support in order to present a proper user-mode model.
For example, many standard user-mode FPU instructions don't exist in
the 68040 hardware, they're done in software. That software is an
inherent part of the 68040 user model. Taking that further, the 68060
throws out several complex integer instructions; to run properly on
the 68060, some additional kernel patches are made to Exec. 

This is really nothing unusual, it's been commonplace on UNIX systems
for years. It's just that on the Amiga, by OS 2.04 (1990), most of
these patches could be applied at boot time, rather than requiring a
completely new kernel as you would for a UNIX system. This has
absolutely nothing to do with the "32-bit-ness" of the OS -- the 68060
is no more or less 32-bit than the 68020. 

Dave Haynie          | ex-Commodore Engineering |   for DiskSalv 3 &
Sr. Systems Engineer |  Hardwired Media Company | "The Deathbed Vigil"
Scala Inc., US R&D   |    Ki No Kawa Aikido     |     info@iam.com

	     "I don't owe you anything!" -Foo Fighters