I remember now about Amdahl's CSIM. Thanks for the lengthy post on it. Cache and NVS sizes were indeed vanishingly small in the 1980s compared to today's models. I remember attending a SHARE session, ca. 1989, in which an IBM cache control unit person from Tucson said that IBM had modeled vast amounts of traced user I/O requests and decided that 4M, or at most 8M, of NVS was all that anyone would ever need to support DASD fast writes. This reminds of me T. J. Watson's prediction in 1943 that "there is a world market for maybe five computers." lol
Bill Fairchild Software Developer Rocket Software 275 Grove Street * Newton, MA 02466-2272 * USA Tel: +1.617.614.4503 * Mobile: +1.508.341.1715 Email: [email protected] Web: www.rocketsoftware.com -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Larry Chenevert Sent: Tuesday, May 04, 2010 7:45 PM To: [email protected] Subject: Re: How to analyze a volume's access by dataset For those who were not there at the time -- in the 80's, when cache and fast-write were first introduced, caches were tiny compared to current technology, and NVS sizes were even smaller -- much smaller. Memory for cache and NVS was quite expensive. Caching and fast-write were, for a short time, specified on a dataset by dataset basis. Many internal marketing tools have corners cut in development (well I guess some companies even cut corners on their products!) and have very rough user interfaces, but not CSIM, which had all the attributes, look and feel of a flagship product. It was not a product, but was a tool for internal people to use -- although it was probably left with some customers. I suppose this tool could have been used to model the performance of different cache algorithms but I doubt it was ever used in that mode. Larry Chenevert ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
