pasm@pur-ee.UUCP (HJ Siegel PASM) (02/05/86)
In article <2987@ncsu.UUCP> hand@ncsu.UUCP (Steven Hand) writes: > >I think OS-9 would be great for the Amiga, but if you want to write your own >quality OS for the Amiga, much of the work has ALREADY BEEN DONE and can be >found in the book > > Operating System Design: The XINU Approach > by Douglas Comer (Prentice-Hall) > He goes on to describe XINU features and discusses their merits when (potentially) integrated with existing Amiga OS capabilites. >You can get a MAGTAPE from the publisher with all this and a CROSS DEVELOPMENT >SYSTEM that runs on VAX Berkeley UNIX 4.1 or 4.2. (Includes C compiler for >LSI-11 microcomputer, linking loader, up/down-loaders, debugger, utilities). >While the book describes an LSI-11 as the target, it mentions that students >have ported XINU to the 68000. Maybe you can get the source for the 68000 >version? Since most of you reading this are more interested in the 68000 than in the LSI-11/02, I'll comment on my experiences with porting XINU to the 68000. I am not one of the ``students" referred to in the previous message. Our laboratory got a tape with XINU and the X-development stuff for the 68000. The compiler, assembler, etc. are vintage-1980 and have lotsa bugs. We chucked it all and use the X-development stuff for the 68000 now distributed with VAX Berk-UNIX. We use our own assembler which is full 68020/68881. We then found that the 68000 ``port" was never really completed - only the assembly language part of XINU was modified (and not very well at that). We had to spent 400-600 man-hours improving and rewriting for multi-user operation, re-writing the tty driver, adding new floppy and winchester disk drivers, etc. We're close to being UNIX 4.1 syscall-compatible. It currently runs on a Motorola MVME 110 CPU board and uses the MVME 320 disk controller. I understand that the students associated with the author (Dr. Comer) got XINU to work on a SUN workstation with a hard disk, but they have not made the same modifications we have. Dr. Comer is a professor in the CS department at Purdue University in West Lafayette, IN 47907. The XINU book is a great alternative to the scatter-shot descriptions of existing operating systems found in other books because it gives the REAL CODE! NO AMBIGUITY HERE!! I highly recommend it as a learning tool for those just getting the urge to set off and start writing an OS of their own. Each time I reread a section in the book, I uncover some elegant and simple programming solution to a problem. Be forewarned though: XINU is a starting point and not really as complete as Steve Hand would have you believe. The elegant and simple solutions given rely on assumptions that we found to be intolerable: no hardware memory management, no protection of users from each other, etc. Yet, after all is said and done, XINU turns out to be considerably smaller than a comparably-featured UNIX kernel. Jim Kuehn, PASM parallel processing laboratory, Purdue-ECN. kuehn@ed.ecn.purdue.EDU pasm@ed.ecn.purdue.EDU