>>some *NIX clones WILL run on 8088's......
>You can write a dos program called *NIX and emulate some of UNIX, but can it
>provide the true memory protection needed for multitasking on a 8088?
>When I say UNIX, I mean UNIX.
Since this group is called *.programmer, I assumed that most people
know how program excutes.
Let's first define what is UNIX, then we can argue whether or not
UNIX can run on 8088.
My description : UNIX is a true multiuser OS, which means
user A1's process P1 can not affect arbitarily
user B1's process P2 running under UNIX.
If we agree on this, we can discuss further, if someone insist
that something that does not satisfy the above criterion a UNIX,
since it name ends with NIX, I quit the discussion.
Now suppose some *NIX is running on 8088 ( I am not knowledgeble enough to
know about Z-80, except that it was 8-bit ), A1's process P1 is preempted
by B1's P2, P2 happens to be a bad program,
It does something like
or mov P1_address garbage
or mov Some_important_register garbage
Is there anything to stop this? No, because the machine see these
instructions perfectly legal. Can we implement protection in software? No.
What is the result? nobody knows, sometimes we have to reboot the machine,
why? maybe the DOS in memory is damaged, so need to re-fetch from disk.
If on a 286, we can run protected mode, use some of the memory as
segment table, some intructions is priviliged, memory access is
checked against the segment table and so on, then the bad guys
will be stopped.
This contrasts in