[TUHS] Mach for i386 / Mt Xinu or other

Clem Cole clemc at ccc.com
Wed Feb 22 11:19:19 AEST 2017


​below... this one made me a laugh a little because it skipped a few steps
that knew (and was a part).​

Once again it was ignorance and little luck that brought us what we got,
not invention nor knowledge.

On Tue, Feb 21, 2017 at 5:58 PM, Wesley Parish <wes.parish at paradise.net.nz>
wrote:

> Now that brings up another reason why I think Linux won. Most of the early
> Linux developers were
> ​ ​
> educated partly in the MS/PC/DR DOS world. They wanted a Unix, but they
> had bought IBM PC clones
> ​ ​
> with MS DOS and were familiar with the DOS way of doing things.
>
​Sort of.... but be careful of a little history here.​




>
> Linux's disk partitioning is very familiar to anyone who's familiar with
> the DOS way of disk partitioning.
>
​Yes, because Linux was not not really enough of UNIX hacker to know that
UNIX partition scheme for PC's was open source and all the code to do it
was available to him.  He wrote his own.​  I remember when I first
encountered the Linux craziness and thinking something on the order of:
 "Why, why are they putting things in DOS partitions ... the BIOS ROMS are
a mess and are already broken... we fixed this already for UNIX on the
386!!!!"

In truth, most end users running real UNIX on a PC/386 were not trying to
dual boot DOS and UNIX, so other than being able to boot the system into
UNIX, they just wanted partitions to map an entire drive and properly load
the read OS (UNIX). So the UNIX scheme, of reserving the disk from the boot
rom, and getting those damned DOS roms out the way ASAP was a fine
solution.  And in the beginning of PC/UNIX that is all that was wanted and
what was there.





> BSD's disk partitioning is a culture shock.
>
The PC Disk partitioning scheme was developed by Intel and the code
released to the UNIX community.  It was the same code base for all 3 System
V ports (which were all done by Interactive Systems under contract for each
of Intel, IBM, and AT&T - one of the best bit of salesmanship Phil Shevrin
ever pulled off IMO -- they did one port and sold it three times).  It was
also used by the AIX/386 folks and eventually usd by Sun.   Part of the
original deal was a project CMU had done with both Intel and IBM for during
that time frame, and between Intel and IBM they got the CMU code made
available (as part of the Andrew project IIRC).   CMU would of course use
this bot/partition code for the Mach port, Jolitz for the BSD port, as well
as all the AT&T base versions.  In fact, it was because of CMU, that UNIX
partition type (type 63) was defined as Intel got Microsoft to add it to
the master database.

The history was something like this as I understand it.... Microsoft starts
to develop Xenix for the 286/68K/Z8000 and maybe one other processor I've
forgotten.  One of the original Xenix ports it to the PC/AT which is 286
based, which it is doing jointly with Intel as well as IBM.  CMU was
working with IBM in Andrew and some how got into that mix and is using
PC/AT as part of the Andrew project.   CMU guys want C tools, so they write
an fdisk/boot system for their stuff.   That migrates back to Intel which
migrates to back to Xenix and Microsoft.   They also made it to UCB as a
version of them is what Jolitz uses for 386BSD.

The question I always wonder was why Andy Tannenbaum did not use those
tools with Minix, but I'm guessing he was trying to do everything virgin
and clean.   Because Linus started with the Minix fdisk, the rest is
history.  Had Linus looked (or asked) the code was very available and he
might have used it too.

The point is that until Minux and Linux, it was actually kinda cool.  All
of the UNIX on a PC/386 platform used the made boot and disk scheme and
hard started with the same C source for boot and fdisk.






> I then tried FreeBSD and I didn't understand the terminology. So I stuck
> with
> what I'd learnt.)
>

That said, as disks kept getting bigger and bigger and the "big iron" folks
had better boot roms, folks like Sun, Masscomp, DEC et al, had much better
support for disk geometry.   The original UNIX on PC partition scheme had
some rough edges, particularly WRT linear addressed drives (such stated
with SCSI, but the PC morphed there also), so BSD took the current scheme
and re-did. Hence, one group PC/UNIX (BSD) folks started to trying to make
the PC boxes do the same things that the Workstations and Mini's could.

So the FreeBSD guys start to extend (sounds like folks from Redmond
eh...)....  Anyway, that's were the new terms like "slice" came from, and I
​admit by the 3rd or 4th rewrite what was in PC/BSD and what was originally
in PC/UNIX differed.

Of course, Microsoft/Intel also had to deal with the bigger and bigger
disks and the same issues withe BIOS that IBM had given us from very small
disks a long time ago but they were not trying emulate "big unix."   So
they did something that worked well for them.    Linux was able to ride the
MS/Intel solutions.   ​
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