Where should the type information be: in tags and descriptors 463

there was this joke in the early MVS time-frame that CMS had a 64kbyte MVT simulator (built into the CMS kernel) and MVS had an 8mbyte MVT simulator (and CMS did a very respectable job with its 64kbyte MVT simulator ... compared to MVS's 8mbyte MVT simulator).

the first deckstop 370 was the xt-370 ... which was a co-processor board for an xt-pc. the CMS applications and orientation was significantly more resource (disk I-O and real storage) hungry compared to dos applications of the period (somewhat analogous to the difficulty they had craming mac-os into the early mac machines).

the initial project was called washington and it was going to ship with 384k bytes memory for the 370 side. the cp kernel was specially modified to do all i-o from interprocessor communication to an application called cp-88 running on the 8088 side (which then do various disk, screen, keyboard, etc i-o).

the combination of the cp kernel fixed memory requires and the cms applications of the period (which typically might be used for interactive computing and-or program development) resulting in severe page thrashing. the page thrashing was aggrevated by the fact that the page i-o had to be pbutted over to cp-88 which then would perform the operation on a 100ms-operation hard disk (when mainframe users were use to doing multiple collected in i-o operations in 16ms or less).

i showed a number of page trashing benchmarks and they then blaimed me for causing the product ship being delayed while they upgraded the memory from 384k to 512k. the extra memory slightly mitigated some of the worst page thrashing scenarios ... but it still couldn't redo the significant memory and disk i-o requirements of the typical cms operations. As a side note, the earlier cp67-cms had been able to support multiple users on 256k byte 360-67.

even when the hardware (real memory sizes and disk thruput) started to catch up with the typical CMS application operational target ... it was still stuck with a lot of the mainframe oriented application pricing structures.

there was a project in the early to mid-80s that looked at redoing a cms-type implementation that would be agile ... somewhat the boyd influence

and portable across a number of different platforms ... but it somewhat collapsed when they started trying to through everything into the project ... including the kitchen sink.

misc. past washington, xt-at-370 postings

--