[email protected] (Avram Friedman) writes: > While they do not grow in in perfect lock step The presence of Big ass > memory comes with big ass dasd volumes (these are the technical terms > of course) Do you know 3350's and 2314s were once used as paging > devices? For that matter do you no the number 2314 was chosen as the > # for a model of disk drive because it was 4 times larger than its > asexual parent the 2311.
original CP67 paged on 2301 fixed-head/track drum ... but it was only 4mbytes ... and "overflow" to 2314. The original code did single page transfer per sio and pure fifo. as undergraduate in the 60s ... i redid 2301 support for "chained requests", so it ordered queued request for maximum transfers per revolution and multiple transfer per sio (both 2301 & 2314 for same arm position) and added ordered seek queueing for 2314. 2301 peak transfers went from about 80/sec to nearly media transfer ... around 270/sec. 2314 thruput increased 2-3 times and degradation (service time increase as load increased) was much more graceful. trivia: later, 3350 had small fixed-head/track option/feature that could be used for paging. however, it didn't have "multiple exposure" like 2305 (fixed-head/track disk, basically multiple subchannel addresses for same device, that could do things like transfers while other requests were still waiting for rotation). I had proposal to do 3350 multiple exposures that would allow doing data transfers for fixed-head area overlapped with arm seek motion. http://www-03.ibm.com/ibm/history/exhibits/storage/storage_3350.html however, there was group in POK that was planning on doing "vulcan" ... an "electronic disk" ... on the lines of "1655" mentioned upthread http://www.garlic.com/~lynn/2017d.html#63 and blocked the 3350 multiple-exposure feature. They then got killed when they were told that customers were ordering all the memory that IBM could produce for processor memory (at higher markup) ... but I wasn't allowed to resurrect the multiple-exposure. As it happened, the "1655" vendor was using memory chips that failed processor memory tests, but could be still be used for electronic disk. longer discussion http://www.garilc.com/~lynn/2006s.html#45 more 2301 mention in this recent comp.arch post (2301 was sort of 2303 but read/wrote four tracks in parallel, 4 times the data transfer rate, 1/4th the number of tracks, each track four times larger) http://www.garlic.com/~lynn/2017d.html#60 Optimizing the Hard Disk Directly later 2305-1 did something similar ... it put every other head on the same track but offset 180degrees ... resulting in half the number of tracks (and half the total capacity) ... and alternatating bytes were on opposides sides. Avg. rotation delay was then only quarter of track (rather than half) ... and data transfer was twice (3mbytes/sec rather than 1.5mbytes/sec) ... doing read/writes from both heads in parallel (on opposite sides of the track, odd on one side, even on the other side). http://www-03.ibm.com/ibm/history/exhibits/storage/storage_2305.html -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
