Unix for 8080/Z80? [Re: WooHoo!! PC/XT Unix anyone?]

From: Frank McConnell <fmc_at_reanimators.org>
Date: Sat Jan 23 11:50:05 1999

Gary Oliver <go_at_ao.com> wrote:
> Damn. I'm home and can't look it up... But I believe I recall something
> called (IIRC) "Micronix" (or something similar) that ran on a Godbout
> or Morrow system. I have some hardware documentation for the system
> that ran it - got it in anticipation of getting one of the S-100 CPU
> boards.

Yep. It was a Morrow thing and I think it ran on the Decision 1
system (not the Micro Decision which is completely different). I ran
into someone once who said he had experience of running Micronix and
told me I did *not* want to try running it. Heh.

> The system had a memory paging system on top of a Z-80 and included
> some fairly sophisticated protection (both memory and I/O) that would
> have permitted a Unix-like system to operate securely.

Likewise my docs and disks (and hardware) are buried in storage, but
from what I remember this is all on the Z80 card and described well
enough to code around in its manual. It divides the Z80's 64KB
address space and the IEEE-696 16MB address space into 4KB pages, so
that any page in the Z80 address space can be mapped to any page in
the -696 space, and it keeps 16 page tables (called "tasks") in RAM on
the Z80 card. Task 0 is special (the "supervisor") in that one of its
pages is the page table RAM. The page table entries have protection
bits that mark a page for various sorts of access, and if the Z80
tried to access memory in a way that wasn't allowed, the card would
force an interrupt in task 0's context so that task 0 could figure out
what to do (which could mean something like increasing the failing
task's memory allocation and retrying the operation).

I think the CPU card for the Decision 1 is the Morrow MPZ80, but can't
remember if I have the part name right or not. It's a fancy IEEE-696
Z80 card.

If anyone has clues on the proper system configuration for Micronix,
I'm interested -- it's been a while, but I did try to get it to boot
once upon a time without much success.

-Frank McConnell
Received on Sat Jan 23 1999 - 11:50:05 GMT