Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!bu.edu!transfer!lectroid!lennox From: lennox@lectroid.sw.stratus.com (Craig Scott Lennox) Newsgroups: comp.os.minix Subject: Re: Minix ... for PDP-11 Message-ID: <1417@lectroid.sw.stratus.com> Date: 28 May 90 16:50:37 GMT References: <1990May28.015301.7341@virtech.uucp> Sender: usenet@lectroid.sw.stratus.com Lines: 32 In-reply-to: rickr@virtech.uucp's message of 28 May 90 01:53:01 GMT 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. -- | flame me at: lennox@shire.hw.stratus.com, Craig Lennox, Stratus Computer | |"Oh boy, virtual memory! Now I'm gonna make myself a REALLY BIG ram disk!" | | Disclaimer: My opinions are covered by section 2b of the Gnu Public | | License and thus do not belong to Stratus Computer. |