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Any operating systems for 68000 (mac classic)?

alectrona2988

Well-known member
I am currently looking for any operating systems other than Mac OS for my 1991 Macintosh Classic M1420. Does anyone know of an OS that can run on an 8MHz 68000 and 2MB of RAM?

 

blitter

Well-known member
None off the top of my head that don't require emulation. The Classic's lack of a MMU is a significant limiting factor.

 

jack

Well-known member
Is XINU available for the Classic? It was designed for the 512K/Plus/SE/II, so you may be able to get it working on your Classic.

 

alectrona2988

Well-known member
I don't know where to get Xinu for M68K. i'm hoping there are other linux distros for 68000. But my classic does have a 120MB SCSI hard drive that works perfectly, but it's slow.

 

jack

Well-known member
So I was missing my XINU floppies at home, but this was on Mac GUI:

http://www.macgui.com/downloads/?file_id=24144

It's unlikely you will be able to get any variant of Linux on an original 68000. The 68000 had a bug where, upon invalid memory access, the processor would be left in an unstable state. This was critical for virtual memory implementations, and hence most UNIX systems made to run on a 68000 used hacks like running 2-processors side-by-side, restoring the state to a valid one on the processor one instruction ahead. Also, the classic lacks an MMU, which Linux requires. Point is: XINU is one of the very few UNIXes that will run on an original 68000 without extra hardware hacks.

 

Gorgonops

Moderator
Staff member
It's unlikely you will be able to get any variant of Linux on an original 68000.


In principle it would be theoretically possible to port uClinux:

http://www.uclinux.org/

to the classic Macintosh. People have gotten running on homebrew 68000 boards with as little as 640k of RAM, although realistically you'd probably want to target a full 4MB configuration to do anything remotely "useful". (And I really am abusing the word "useful" here.)

If you were *really* hardcore you could try porting the "MINI-UNIX" variant of Sixth Edition Unix for the PDP-11. It was the original "Unix-without-an-MMU" implementation that inspired all those that followed. (XINU, Idris, early versions of XENIX and MINIX, Coherent, etc.) Considering Mini-UNIX could run on machines with as little as 24K of RAM you'd have a lot more breathing room than you get with uClinux, assuming you're willing to restrict yourself to appropriate 1970's vintage programs. ;)

 
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Gorgonops

Moderator
Staff member
... and as a more generic comment: alternate "bare-metal" OSes for the original Macs are *really* rare. I'll be blunt and admit that I can't actually name one off the top of my head. All the UNIX-oids I can actually think of for those, like XINU, MachTen, and MacMinux are packaged as Macintosh application binaries and depend on MacOS system calls for all I/O. There are a number of reasons why the Mac is *very* difficult to "drive" from bare-metal, with the main one being that much of the hardware (especially the floppy drive controller) depend on extremely timing-critical software drivers in ROM to function, and said drivers (along with the rest of the ROM) are very tightly coupled to the structure of MacOS itself. Apple never documented how to bring the system up from bare metal, which is why even on the later 68k (and some PowerPC) Macs that *can* run a real UNIX still rely on using a MacOS application run after booting a Mac System partition as a bootloader. (Even Apple's own A/UX does this.)

To restate the OP's question, can anyone actually name ANY alternate OS for 68000 Macs that runs bare metal?

 

Gorgonops

Moderator
Staff member
Or the CP/M 68k ports?


I was going to comment myself that there are a lot of claims that CP/M-68k was ported to the Mac, but no one seems to actually be able to point to real evidence that it was ever released. It did make it onto the Lisa, but the Lisa's firmware design was somewhat more amenable to third-party development. (There was a Xenix port for it as well.)

 

alectrona2988

Well-known member
So I was missing my XINU floppies at home, but this was on Mac GUI:

http://www.macgui.com/downloads/?file_id=24144

It's unlikely you will be able to get any variant of Linux on an original 68000. The 68000 had a bug where, upon invalid memory access, the processor would be left in an unstable state. This was critical for virtual memory implementations, and hence most UNIX systems made to run on a 68000 used hacks like running 2-processors side-by-side, restoring the state to a valid one on the processor one instruction ahead. Also, the classic lacks an MMU, which Linux requires. Point is: XINU is one of the very few UNIXes that will run on an original 68000 without extra hardware hacks.
Thanks, but I need to write it to floppy. How can I do this?

 

jack

Well-known member
XINU won't fit on a single floppy. Follow the instructions in README.mac: copy the directory to /XINU on the system, setup Aztec C in /C, etc. You're going to need a copy of Aztec C. No idea where to find this anymore...

 

alectrona2988

Well-known member
XINU won't fit on a single floppy. Follow the instructions in README.mac: copy the directory to /XINU on the system, setup Aztec C in /C, etc. You're going to need a copy of Aztec C. No idea where to find this anymore...
Oh, okay! I have MacDisk and it works great with my 1.44MB floppies as I can just copy some files over and then erase the floppy and then copy more. Also, here's a tip: If you need to write system install disks on a Windows PC, format it with your mac and then put the disk in a windows PC (a USB floppy works fine) and then download rawwrite, then write the floppy image. It works like a champ for me.

 
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