[Info-vax] OT: news from the trenches (re: Solaris)

[glen herrmannsfeldt]

lists at openmailbox.org wrote:
> On 12 Mar 2015 17:44:41 -0400
> Scott Dorsey via Info-vax <info-vax at rbnsn.com> wrote:
 
(snip) 
>> They did in fact design a low-end 370 chip for personal computers, which
>> was actually a 68k with different microcode to emulate a 370.  And they
>> made the PC/370 with it.
 
>> They didn't get Gates to build DOS for the /370 because the whole point of
>> running a /370 is to run existing code.  They already had DOS/370.
 
> Ok, let's not get too confusing for those not familiar. DOS/370 has no
> relation to MS/DOS or IBM PC/DOS, preceding both by many years. Still in
> production today btw as z/VSE http://www-03.ibm.com/systems/z/os/zvse/

I don't think there is DOS/370.  There is DOS/360, built for machines
too small to run OS/360. It was supposed to only last until people would
move up to OS/360. Later, there was DOS/VS for small 370's, and
DOS/VSE in later years, leading to z/VSE. 
 
> I never saw an XT/370 so I don't know what they ran. Looking quickly over
> the net it appears they didn't emulate the full instruction set. Do you
> happen to know what they were actually capable of and used for? It seems
> they could not boot or run any mainframe OS.

The XT/370 and AT/370 run VM/PC, a customized version of VM/370.
The CP (virtual machine) part runs partly on the 370 and partly on
the 8088 or 80286, communicating with interrupts and shared memory.
I believe the CMS is the same as VM/SP's CMS. 

Original VM/370 CMS runs with 800 byte disk blocks, but later VM's
allow for 1K, 2K or 4K disk blocks, much easier to support on a PC
file system.

Also, the DAT (virtual address) system works completely different
from real S/370 DAT.

But the P/370 does everything the way it is supposed to, for
later implementations of S/370. There is microcode for XA/370 and,
on P/390 (with more control store) ESA/390.
 
>> >Of course, a large corporation is prevented from going that way because
>> >making an affordable 370 based computer is tantamount to cannibalasing
>> >higher end sales. DEC also suffered that fate.
 
>> And it's a small market item too, really.  But the PC/370 was actually
>> very cheap considering what it was and what you could do with it.
 
> Ditto for the P/390. For 30,000 bucks you could run a real development shop
> with 30-50 guys. They actually ran honest to goodness copies of VM and
> OS/390.

-- glen