4 Jul
2016
4 Jul
'16
11:08 a.m.
On Thursday, 30 June 2016 at 8:49:26 -0700, Larry McVoy wrote:
On Thu, Jun 30, 2016 at 11:32:08AM -0400, Dan Cross
wrote:
Not directly related, but I don't know which other message in this
subthread is more relevant:
Don't forget the constraints on the PC design. The IBM model number
was 5150: it was a last-ditch attempt to salvage the not very
successful 5100 series. To do so they outsourced things that IBM
would normally have developed in-house. And that meant taking
existing products, not creating new ones. The success of the PC
caught IBM by surprise, like the 704 30 years earlier.
At the time IBM talked to Microsoft, Microsoft's OS plans were clear:
XENIX. See the August 1980 (I think) issue of Byte, where there's a
long story about why XENIX is the correct choice of operating system.
You can be sure that Microsoft tried to sell that first. But instead
they had to go out and buy QDOS from Seattle Computer Products.
And why? Yes, the 8088 was a reasonably fast processor, so fast that
they could slow it down a little so that they could use the same
crystal to create the clock both for the CPU and the USART. But the
base system had only 16 kB memory, only a little more than half the
size of the 6th Edition kernel. Even without the issue of disks
(which could potentially have been worked around) it really wasn't big
enough for a multiprogramming OS.
From my point of view, I think the real shame is that Microsoft didn't
do a better job of their stated aim to make MS-DOS 2.0 more like
Unix. We're still living with those issues today.
Greg
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Something I never understood about the IBM PC:
even the 8088 machine was
fairly beefy compared to e.g. a PDP-11/20. The 6th Edition Unix kernel was
objectively pretty small and understandable; mini-Unix showed that that
sort of software could be used on a machine without an MMU. I've never
understood why IBM didn't just write a real OS in a high-level language
instead of saddling the world with MS-DOS. Perhaps it's naive of me, but
even if they didn't use Unix directly, it was an existence proof that such
a thing was possible. I suppose, again, it was less a technical issue and
more a business issue, or perhaps I'm underestimating the amount of work or
missing some of the technical complexities.
I wonder if they just didn't know. Unix was Bell Labs and
Universities for the most part. Was the timing such that they may
not have been aware of Unix? Or maybe they knew about Unix but
thought it was for the vax?