[rescue] More IBM emulation fun

[Scott M]

On Mon, 9 Feb 2009 20:04:36 -0600, Bill Bradford wrote:
> ... VM/370 ... documentation ... 
http://www.bitsavers.org/pdf/ibm/370/vm370/

At this URL, this doc:  Introduction_To_VM370_Course_Jul75.pdf
has this chapter heading:  "VIRTUAL MACHINE DESCRIPTION". 
Virtualization in 1975?  Really? 
I guess I should not have been surprised, since the "VM" in VM370 
stands for "Virtual Machine".  
http://en.wikipedia.org/wiki/VM370
However with so little memory available, it seems strange that 
anyone would want to put more than one OS on a machine of that era. 
Page 8 of this doc shows a "256K DOS BATCH" virtual machine running 
on a S/370 Model 145 along with five "320K CMS" virtual machines. 
But DOS didn't exist in 1975!   -Turns out this isn't MS-DOS, but 
IBM DOS/360 or some variant of it: 
http://en.wikipedia.org/wiki/DOS/360
Maybe DOS/360 and CMS were single-user and virtualization was a way 
to make the machine multi-user?  Or maybe IBM had the same problems 
as today where code needs to be isolated because it tries to write 
to memory that belongs to someone else? 
 
-Scott M