DOS code in CP/M? Revisited...

Guy Sotomayor Jr ggs at
Fri Jul 15 13:52:58 CDT 2016

> On Jul 15, 2016, at 11:30 AM, Chuck Guzis <cclist at> wrote:
> On 07/15/2016 11:10 AM, Liam Proven wrote:
>> We don't appreciate how much faster modern PCs are than the old
>> ones, because modern PC OSes are so appallingly slow and bloated.
> Reminds me of a conversation that I had with Greg Mansfield back in the
> mid-80s when he was working for Cray.   I was grousing about the time
> spent recompiling the BSD kernel on a VAX 11/750, even when streamlining
> the process through partial recompilation (i.e. compiling only those
> parts needing it).  Greg was working with, IIRC, UniCOS at the time and
> confided that on an X/MP he didn't bother with partial
> recompilation--there was no practical time savings realizable.
> Flash back to 1975 when recompiling the STAR OS kernel on a dedicated
> STAR 1B took all night--assuming that the machine stayed up that long.

When I first started working on the IBM S/23, a complete build took a week
(yes, 7 days…if we were lucky).  Debugging and fixing was mostly keeping
a notebook of patches to applied to the previous build.  “fixes” were first
developed by patch and then actual source changes were made.  We usually
spent a day just patching the “fixes” when a new build was released because
what we had to do in a patch vs the real change were often different.

Eventually someone wrote a cross build environment for the Series/1 and the
build went down to overnight (yea!).

You may ask “It was IBM why didn’t you use the S/370 mainframes?”.  It was
accounting.  We could “buy” equipment (Series/1 and the like) and it was a
capitol expense.  We were billed (at a ridiculous rate as I recall) for Mainframe
time out of the department expense budget.  The expense budget was very
closely monitored.  The capitol budget not so much.

Kids have it so much easier now.  ;-)

P.S. A full build for the board I work on (OS and creating the boot image) for
work takes < 1 hour.  The firmware I’m working on takes just 2-3 seconds to
build!  This is on a PC with a 3.2GHz Skylake i7 with SSDs.  ;-)

TTFN - Guy

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