z/VM usability
(too old to reply)
Anne & Lynn Wheeler
2007-05-06 23:14:27 UTC
I know there is no commercial value in it, so it won't
happen, but wouldn't it be nice if IBM realeased a
software emulation that worked like the original
XT/370 that emulated both the Hardware and CP calls
and so would allow CMS itself to be run native on
Linux or Windows...
.. oh and of course would license CMS for such
an evironment.
XT/370 was codenamed washington ... stripped down CP kernel running on
modified 68k processor that provided 370 emulation (for problem and some
privileged instructions). The "370" had its own dedicate processor
memory. Running under dos was a program called "cp/88" and the CP kernel
would communicate with "cp/88" for emulation of I/O operations
(i.e. cp/88 provided real device i/o support and communicated back and
forth with the cp kernel).

the original model had 384k "370" memory ... and I did some application
studies which showed that after the fixed cp kernel memory requirements
... that cms applications frequently would "page thrash" in the
remaining real memory. Exaserbating the problem was that all disk i/o
(both cp paging and cms file i/o) involved communication with cp/88
which would then simulate the operations on XT hard disk that had
110millisecond avg. access.

the publishing of the elapsed time & page thrashing results resulted in
a corporate decision to ship the product with 512k "370" memory
... which involved a six month schedule slip ... which lots of people
blaimed on me.

However, in this time window ... I was allowed to incorporate an
enhanced page replacement algorithm (over and above what i was able to
ship in the vm370 resource manager) ... and CMS "paging access method"
filesystem support ... i.e. page-mapped operation ... which I had
originally done on cp67/cms ... but never shipped in standard vm370

the problem was that normal CMS operations are highly disk intensive.
DCSS sharing of applications on mainframes were somewhat able to
compensate for some of this (by having programs & applications already
available in real storage because of use by other users). However, in
the xt/370 configuration none of this was applicable ... there wasn't
enuf real storage for such caching ... and since it was a single user
system ... there wasn't any "sharing" use. however, I had demonstrated
avg of 300percent (or better) thruput improvement with the paged mapped
cms filesystem support for disk intensive operations. The page mapped
CMS filesystem support also allowed for asyncronous operation on program
loading ... allowing large block load of CMS "module" into whatever
available real storage ... but also allowing some asyncronous overlap of
CMS application execution with loading of the program (keeping all the
asyncronous activity straight and hidden from cms by playing games with
page invalid/valid bits). The page mapped CMS filesystem support also
had some enhancements for attempting to do contiguous (physical)
allocation when MODULE was generated (and/or written to disk) ... which
could be subsequently leveraged when program was loaded.

the same adapter board was later made available in ATs and called

the "follow-on" was a full-blown 370 in separate box with 4mbytes
of memory code-name "a74" (for the department in POK) and released
as 7437 ... old email with announcement of 7437

old email that includes list of source update files that I had to the cp
kernel as part of A74 support ("dmkpam" is the source routine containing
the cp changes supporting paged mapped operation).
http://www.garlic.com/~lynn/2003f.html#56 ECPS:VM DISPx instructions

other past posts mentioning A74:
http://www.garlic.com/~lynn/2000e.html#55 Why not an IBM zSeries workstation?
http://www.garlic.com/~lynn/2000e.html#56 Why not an IBM zSeries workstation?
http://www.garlic.com/~lynn/2001i.html#19 Very CISC Instuctions (Was: why the machine word size ...)
http://www.garlic.com/~lynn/2001i.html#51 DARPA was: Short Watson Biography
http://www.garlic.com/~lynn/2002d.html#4 IBM Mainframe at home
http://www.garlic.com/~lynn/2002l.html#27 End of Moore's law and how it can influence job market
http://www.garlic.com/~lynn/2003h.html#40 IBM system 370
http://www.garlic.com/~lynn/2003m.html#15 IEFBR14 Problems
http://www.garlic.com/~lynn/2004l.html#65 computer industry scenairo before the invention of the PC?
http://www.garlic.com/~lynn/2004m.html#7 Whatever happened to IBM's VM PC software?
http://www.garlic.com/~lynn/2004m.html#8 Whatever happened to IBM's VM PC software?
http://www.garlic.com/~lynn/2004m.html#10 Whatever happened to IBM's VM PC software?
http://www.garlic.com/~lynn/2007c.html#14 How many 36-bit Unix ports in the old days?
http://www.garlic.com/~lynn/2007g.html#76 The Perfect Computer - 36 bits?

old email mentioning some of the activity porting enhancements from
cp67 to vm370

misc. past posts mentioning some aspects of the resource manager
and/or page replacement algorithms
and other posts mentioning the paged mapped cms filesystem work

and past posts mentioning washington, xt370, at370 and/or getting
blaimed for six month slip in scheduled to increase real storage
from 384k to 512k
http://www.garlic.com/~lynn/94.html#42 bloat
http://www.garlic.com/~lynn/96.html#23 Old IBM's
http://www.garlic.com/~lynn/2000e.html#52 Why not an IBM zSeries workstation?
http://www.garlic.com/~lynn/2001f.html#28 IBM's "VM for the PC" c.1984??
http://www.garlic.com/~lynn/2001i.html#20 Very CISC Instuctions (Was: why the machine word size ...)
http://www.garlic.com/~lynn/2001k.html#24 HP Compaq merger, here we go again.
http://www.garlic.com/~lynn/2002b.html#45 IBM 5100 [Was: First DESKTOP Unix Box?]
http://www.garlic.com/~lynn/2002d.html#4 IBM Mainframe at home
http://www.garlic.com/~lynn/2003f.html#8 Alpha performance, why?
http://www.garlic.com/~lynn/2003h.html#40 IBM system 370
http://www.garlic.com/~lynn/2004h.html#29 BLKSIZE question
http://www.garlic.com/~lynn/2004m.html#7 Whatever happened to IBM's VM PC software?
http://www.garlic.com/~lynn/2004m.html#10 Whatever happened to IBM's VM PC software?
http://www.garlic.com/~lynn/2004m.html#11 Whatever happened to IBM's VM PC software?
http://www.garlic.com/~lynn/2004m.html#13 Whatever happened to IBM's VM PC software?
http://www.garlic.com/~lynn/2005f.html#6 Where should the type information be: in tags and descriptors
http://www.garlic.com/~lynn/2005f.html#10 Where should the type information be: in tags and descriptors
http://www.garlic.com/~lynn/2006.html#10 How to restore VMFPLC dumped files on z/VM V5.1
http://www.garlic.com/~lynn/2006f.html#2 using 3390 mod-9s
http://www.garlic.com/~lynn/2006j.html#36 The Pankian Metaphor
http://www.garlic.com/~lynn/2006m.html#56 DCSS
http://www.garlic.com/~lynn/2006n.html#5 Not Your Dad's Mainframe: Little Iron
http://www.garlic.com/~lynn/2006n.html#14 RCA Spectra 70/25: Another Mystery Computer?
http://www.garlic.com/~lynn/2006y.html#29 "The Elements of Programming Style"
http://www.garlic.com/~lynn/2006y.html#30 "The Elements of Programming Style"
http://www.garlic.com/~lynn/2007.html#1 "The Elements of Programming Style"
http://www.garlic.com/~lynn/2007d.html#7 Has anyone ever used self-modifying microcode? Would it even be useful?
http://www.garlic.com/~lynn/2007d.html#25 modern paging
http://www.garlic.com/~lynn/2007e.html#5 Is computer history taugh now?
Anne & Lynn Wheeler
2007-05-07 04:12:22 UTC
This post might be inappropriate. Click to display it.
Brian Inglis
2007-06-04 09:47:46 UTC
fOn Sun, 06 May 2007 22:12:22 -0600 in alt.folklore.computers, Anne &
Post by Anne & Lynn Wheeler
Well, it's been nigh on 40 years that CMS has been around. Seems like a
committment to me. CMS is here to stay. If all the people with z/OS
get z/VM and [re]discover CMS, who knows what might happen? "Never say
http://www.garlic.com/~lynn/2007j.html#41 z/VM usability
well, cms (as in cambridge monitor system) started on cp40 (cambridge had
gotten a 360/40 and did the hardware modifications to implement virtual
memory ... pending getting 360/67) ... cambridge got 360/67 in 1967 and
morphed cp40 into cp67 ... so it has been 40yrs (in part, CMS work
could even start on real 360/40 before cp40 was operational)
from Melinda's history
By September of 1965, file system commands and macros already looked
much like those we are familiar with today: ``RDBUF'', ``WRBUF'',
``FINIS'', ``STATE'', etc
It was also in the aftermath of killing FS that POK convinced the
corporation to kill the vm370 product, shutdown the vm370 product group
and move all the people to POK to help accelerate the mvs/xa development
schedule (again attempting to make up lost time in 370 product pipeline
resulting from the FS distraction). Eventually Endicott was able to
salvage the vm370 product mission.
That POK move convinced the IBM customers (most had VM and many also had
MVS) in this town that IBM was not considering its customers' best
interests, and it was time to start moving to enterprise SUN boxes,
which led to marginal future for major OS staff and IBM support staff,
which sped up the transition, resulting in remaining legacy apps being
run on one machine in an IBM owned bureau, supported by IBM, and most
IBM staff in the city getting packages or finding jobs elsewhere.
So it is with the cariboo!
Thanks. Take care, Brian Inglis Calgary, Alberta, Canada

***@CSi.com (Brian[dot]Inglis{at}SystematicSW[dot]ab[dot]ca)
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