Robert Wessel <robertwess...@yahoo.com> writes: > IBM shipped about 20 360/91s, then a couple of 360/95s with a > redesigned memory subsystem, then the 360/195 which re-implemented the > same machine on a faster, denser logic process, then that modified was > to include the basic S/370 extensions (no virtual memory) and shipped > as the 370/195. About 40 machines of all four types (combined) were > shipped.
in the 70s, the 195 people sucked me into doing some stuff with them on 370/195 "multiprocessor" that never shipped ... basically red/blue multithreading mentioned here http://people.cs.clemson.edu/~mark/acs_end.html the above also includes some other discussion of 195 ... although primarily '60s 360 ACS ... which got canceled because executives thought that it would advance the state-of-the-art too fast and they would loose control of the market ... aka acs/360 would be significantly more cost-effective machines (also describes some of the ACS features that eventually show up in the 1990 ES/9000) one of the things they told me was that another difference between 360/195 & 370/195 (besides the non-virtual memory 370 instructions) was hardware instruction retry ... which greatly improved reliability. 195 execution units would do 10mips but required careful programming for the pipeline ... which did out-of-order execution ... but not branch preduction or speculative execution ... so conditional branches would drain the pipeline. as a result, most codes ran around 5mips. motivation for red/blue multitreading was the 10mips execution units would be kept busy by two 5mip threads. recent posts mentioning 370/195 http://www.garlic.com/~lynn/2015.html#27 Webcasts - New Technology for System z http://www.garlic.com/~lynn/2015b.html#61 ou sont les VAXen d'antan, was Variable-Length Instructions that aren't this describes decision to make all 370 machines virtual memory ... basically MVT virtual memory allocation was so bad that typical region size had to be four times larger than what was being used ... a 1mbyte 370/165 running four regions could get 16 regions with virtual memory and still have little or no paging. http://www.garlic.com/~lynn/2011d.html#73 Multiple Virtual Memory however, retrofitting 370 virtual memory hardware to 370/165 (for 165-II) was no trivial task ... eventually they decide to drop several 370 virtual memory features because they were too hard for the 165 ... other machines would also have to drop those features ... and software groups that had already written code using the dropped features would have to be reworked. -- 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
