On 26 April 2010 19:02, Shmuel Metz (Seymour J.) <shmuel+ibm-m...@patriot.net> wrote: > In <4bd491ce.5010...@ync.net>, on 04/25/2010 > at 02:02 PM, Rick Fochtman <rfocht...@ync.net> said: > >>I suspect that 2305 was an outgrowth of the 2302, not necessarily a >>"new" device. > > I don't have any information on that, although the platters certainly > looked similar to those on the 1301, 1302 and 2302.
Where did the 2301 fit in? IIRC that was a true drum. We had one in the early 1970s on MVT on both a /65 and a /165, but support was dropped in MVS. >>The 2305 was available with selector channel interfaces >>before the blk-mux interfaces. At NCSS we were told that it took a >>complete selector subchannel, with eight "exposures", to function >>properly so we configured them (16 devices) to run off 2860 Selector >>channels hanging off a 370/168 system. > > The 2880 was first announced for the S/360; the S/370 was not announced > until 1970, a year after the 360/85, and the original announcement did not > include the 370/168. I'd guess that your management simply did not want to > spend the money on a 2880. The 2880 wasn't announced for all S/360 models, though. In S/370 architecture there is a block multiplexing control bit in Control Register 0. S/360 had no architected control registers (yeah, I know - the /67 did), but perhaps they added them on the /85 and /195? Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
