Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!wuarchive!udel!mmdf From: MAB01057%UFRJ.BITNET@cornellc.cit.cornell.edu (Marcelo Amarante Ferreira Gomes) Newsgroups: comp.os.minix Subject: Re: Minix ... for PDP-11 Message-ID: <20434@nigel.udel.EDU> Date: 28 May 90 21:39:28 GMT Sender: mmdf@udel.EDU Lines: 29 In a previous article, Craig Scott Lennox tells us that the Atari 800 doesn't really have 64K of memory. That's true of the *really old* Atari's. The 800XL's do have entire 64K, although it may be a little harder to use the memory above 48K, since that memory must be switched on and off as you turn the machines's ROM on and off at the very same address space. That place seems to be a good one to store Unix user programs. Note also that the newer 8-bit Atari's (like the 130XE) even have more than 64K (128K ?), also switchable. The kernel could then run in the lower, say, 10 or 20K of available RAM. I hear you saying: nonsense! No one could ever write such a small kernel! Not on *that* machine! Just remember that all the I/O part is already written, tested and debugged (to some extent - there are some known bugs :-( ) and is available in that ROM that must be switched on and off. Everything one has to do is to write a little scheduler, assign some memory usage conventions, write a compiler that uses them and put everything together. The scheduler is even easy to be written with the extensive interrupt support you've got on the Atari. It's really a challenge, but it can be done. Do you remember OS/9? It runs on a 6809, wich is a processor a little bit more powerful than good old 6502. And it runs fast! This last item is not so easy on an Atari because of hardware limitations I mentioned before (another article). Unix on an Atari 800 (even the old one) is not science fiction. It may not be practical, but is sure an excellent academic exercise. Marcelo A. Ferreira Gomes (Wally Gator)