The following message is a courtesy copy of an article that has been posted to bit.listserv.vmesa-l,alt.folklore.computers as well.
Dave Wade wrote: > 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 release. 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 AT/370. 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 http://www.garlic.com/~lynn/2000e.html#email880622 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 http://www.garlic.com/~lynn/2006v.html#email731212 http://www.garlic.com/~lynn/2006w.html#email750102 http://www.garlic.com/~lynn/2006w.html#email750430 misc. past posts mentioning some aspects of the resource manager http://www.garlic.com/~lynn/subtopic.html#fairshare and/or page replacement algorithms http://www.garlic.com/~lynn/subtopic.html#wsclock and other posts mentioning the paged mapped cms filesystem work http://www.garlic.com/~lynn/subtopic.html#mmap 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?
