cvitu...@hughes.net (Carmen Vitullo) writes: > I remember DRUM storage, just never worked with it, the only other > DRUM storage I saw was at a tour at a data center somewhere in Jersey, > my BIL worked there, did some work with NYSE I believe, and they were > mostly all Univac or PDP systems and I saw what I think was a solid > state drum storage unit, at 19 or 20 I was quite impressed.
2303 drum was fixed-head per track about 4mbyte ... ran at 2314 transfer and could be connected to later 360/30 (recent discussion on facebook ibm retiree group). 2301 was pretty much 2303 ... but read/wrote four heads in parallel, 1/4th the number of tracks, tracks four times larger, four times the transfer speed (1.2mbytes/sec). IBM System/360 Component Descriptions- 2841 and Associated DASD http://www.bitsavers.com/pdf/ibm/28xx/2841/GA26-5988-7_2841_DASD_Component_Descr_Dec69.pdf 2302 (never heard of any actually installed) pg39-63 ... looks a little bit like the later 2305 fixed-head disk. has two access heads, one for the inner 250 tracks and one for the outer 250 tracks. 2303 "drum", pg 73-76. 2301 drum http://www.bitsavers.com/pdf/ibm/28xx/2820/A22-6895-2_2820_2301_Component_Descr_Sep69.pdf 2301 drum was traditional "paging" drum for 360/67 virtual memory systems ... officially TSS/360 .... but IBM science center did virtual machine (cp67) system, Univ. of Mich did MTS system, Stanford did Orvyl (where Wylbur editor originated). standard 2301 (paging) format was nine 4k pages on pair of tracks (with record spanning the end of one track and the start of next). Original CP67 delivered to the univ. Jan1968 did single page transfer per I/O and both disk & drum requests were executed purely FIFO. Drum requests would cost half rev. per each transfer ... peaking at 80 page I/Os per second. I did ordered chained I/O and could peak at 270 page I/Os per second. I also did ordered seek queuing for disk, helping with both (overflow) disk paging as well as file I/O operation throughput. (later) 2305 fixed head disk, model 2 11.2mbytes, 1.5mbyte/sec transfer, avg access 5ms. model 1 had same number of heads but they were installed on half the number of tracks with pair of heads at 180degree offset on same track. 5.4mbyte capacity (half m2), 2.5msec avg. rational delay (half m2), and 3mbyte/sec transfer (twice m2). Transfer would occur on pairs of heads in parallel, and with pairs of head on opposite side of platter, it only had to avg. 1/4 revolution before start of record came under pair of heads (even/odd pairs on opposite side of platter). https://www-03.ibm.com/ibm/history/exhibits/storage/storage_2305.html In the early 80s, IBM cut deal with vendor for "1655" electronic disks used by internal datacenters ... they had two modes of operation, native mode and 2305 emulation mode. They were volatile (lost data when power was lost) ... so were limited to paging operations. They were limited to 2305 channel data transfer and were more efficient at low to medium loading (no rotational delay) ... but less difference at heavy loading (since 2305 ordered chained request would already be running at near transfer speed). some recent posts mentioning 1655 http://www.garlic.com/~lynn/2016d.html#24 What was a 3314? http://www.garlic.com/~lynn/2016f.html#23 Frieden calculator http://www.garlic.com/~lynn/2017b.html#68 The ICL 2900 http://www.garlic.com/~lynn/2017b.html#69 The ICL 2900 http://www.garlic.com/~lynn/2017c.html#26 Multitasking, together with OS operations http://www.garlic.com/~lynn/2017d.html#63 Paging subsystems in the era of bigass memory http://www.garlic.com/~lynn/2017d.html#65 Paging subsystems in the era of bigass memory http://www.garlic.com/~lynn/2017e.html#36 National Telephone Day I got to play disk engineer in bldgs 14&15 from mid-70s through early 80s ... some past posts http://www.garlic.com/~lynn/subtopic.html#disk 3350 offered fixed-head feature for limited number of cylinders ... but didn't have multiple exposure support (like 2305) so couldn't do concurrent channel programs for the moveable head portion and the fixed-head portion. I had project to add multiple exposure to 3350 with fixed head feature (so could overlap fixed head transfer with seek operations). There was a group in POK planning on VULCAN, for electronic disk ... that got it killed because they thought it might compete with them in the paging market. Eventually VULCAN gets canceled, they were told that IBM was already selling all the electronic memory it could make for processor memory at higher markup ... but it was too late to resurrect multiple exposure support for 3350 fixed head feature. -- virtualization experience starting Jan1968, online at home since Mar1970 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
