Path: utzoo!attcan!uunet!samsung!usc!ucsd!helios.ee.lbl.gov!nosc!crash!pnet01!jca
From: jca@pnet01.cts.com (John C. Archambeau)
Newsgroups: comp.os.minix
Subject: Re: Minix ... for PDP-11
Message-ID: <2869@crash.cts.com>
Date: 29 May 90 01:16:01 GMT
Sender: root@crash.cts.com
Organization: People-Net [pnet01], El Cajon CA
Lines: 44
X-Local-Date: 28 May 90 18:16:01 PDT

lennox@lectroid.sw.stratus.com (Craig Scott Lennox) writes:
>In article <1990May28.015301.7341@virtech.uucp> rickr@virtech.uucp (Rick Rodman) writes:
>
>   I also note in the discussion about bringing up Minix on the 6502 that
>   there have been many comments about the PDP-11.
>
>Mostly along the lines of "Well if 64K PDP-11's can run Unix, than why not
>64K Atari 8-bits?".  The problem with this reasoning is that it takes a LOT
>more 6502 than PDP-11 code to accomplish the same tasks; with only 3
>special purpose 8-bit registers on the 6502 compared to the 11's five 
>general purpose 16-bit registers, and none of the fancy addressing modes
>of the 11 on the 6502
>
>   As for the Atari 8-bit:  I have Abacus C for the C-64 here...:-}
>   Seriously, don't forget that the 6502 has a fixed, 256-byte stack at
>   0100 hex.
>
>Well, that's not SUCH a problem, since you're designing an O/S from the ground
>up you can simply implement your own stacks in software.  The biggest problems
>I've run into have to do with using 8-bit registers to access a 16-bit address
>space (especially the lack of word operations -- ick!) and of course the
>fact that the Atari 800's 64K is not all RAM (12K is ROM, and 4K DOESN'T
>EVEN EXIST!?!?!?!?!).
>
>But all in all, getting a Un*x-like O/S to run on your old Atari 800 is
>probably the ultimate in a hacking challenge, and I've been having a hell of
>a time.

Yea, but how are you going to implement the C compiler?  Best C compiler
I ever saw for the Atari 8-bit didn't even support structures.  Are you
going to write it all in *gasp* assembly?  Maybe Action! by OSS, perhaps?

Hell of a time is an understatement.
 
     // JCA

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