Sender: eric@ruckus.brouhaha.com From: Eric Smith Newsgroups: comp.arch,alt.folklore.computers Subject: IBM XT/370 and AT/370 (was Re: Computer of the century) References: <84sgc0$mnv$1@mail.ic.uva.nl> <3872047A.73F83228@bellatlantic.ne <84ui3b$gmi$1@nntp6.u.washington.edu> X-Disclaimer: Everything I write is false. Organization: Eric Conspiracy Secret Labs X-Eric-Conspiracy: There is no conspiracy. Date: 05 Jan 2000 15:51:44 -0800 Message-ID: Lines: 21 X-Newsreader: Gnus v5.5/Emacs 20.3 NNTP-Posting-Host: ruckus.brouhaha.com X-Trace: 5 Jan 2000 16:28:16 -0800, ruckus.brouhaha.com Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news.ifi.unizh.ch!newsfeed.rhein-neckar.de!news.rhein-neckar.de!newsfeed.ision.net!ision!diablo.theplanet.net!newsfeed.berkeley.edu!enews.sgi.com!news.sgi.com!news.spies.com!ruckus.brouhaha.com Xref: chonsp.franklin.ch alt.folklore.computers:47502 I wrote: > It took one special remicroprogrammed 68000 which executed the majority > of the 370 instruction set, one standard 68000 that was used to simulate > the instructions not implemented by the special one, and a special > version of the 8087 floating point coprocessor (apparently modified to > support the 370's non-IEEE format). dpeschel@u.washington.edu (Derek Peschel) writes: > I trust you but I just want to make sure you didn't make a typo. We're > talking about the 68000 (by Motorola) plus the 8087 (by Intel)? Yes. The 68851 wasn't even close to availability at that time. > What kind of bus arrangements did IBM have to use to hook them together? I don't have schematics, so I have no idea. Presumably either the modified microcode of the special 8087 made it easier to use by giving it a peripheral-like interface, or else they simulated the 8086 coprocessor interface in software or emulated it in hardware. ###### Sender: lynn@LYNNPC Newsgroups: comp.arch,alt.folklore.computers Subject: Re: IBM XT/370 and AT/370 (was Re: Computer of the century) References: <84sgc0$mnv$1@mail.ic.uva.nl> <3872047A.73F83228@bellatlantic.ne <84ui3b$gmi$1@nntp6.u.washington.edu> Reply-To: Anne & Lynn Wheeler From: Anne & Lynn Wheeler Message-ID: Organization: Wheeler&Wheeler Lines: 28 User-Agent: Gnus/5.070099 (Pterodactyl Gnus v0.99) Emacs/20.4 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Thu, 06 Jan 2000 02:13:31 GMT NNTP-Posting-Host: 209.63.28.138 X-Complaints-To: support@adcomsys.net X-Trace: news-west.eli.net 947124811 209.63.28.138 (Wed, 05 Jan 2000 19:13:31 MST) NNTP-Posting-Date: Wed, 05 Jan 2000 19:13:31 MST Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!newsfeed.berkeley.edu!enews.sgi.com!sdd.hp.com!news-west.eli.net!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:47483 The XT/AT/370 didn't support all of the 370 instruction set ... there were omissions in the supervisor instructions. It ran a modified version of VM/370 that took into account the supervisor differences, for instance I/O was done by communicating with a monitor program running on the 8088/80286 ... which then did actual disk accesses, keyboard operation, display, etc. It also had a modified version of one of my page replacement algorithms and my CMS page-mapped file support (which was never shipped, other than internally ... or possibly AT&T longlines, in the standard product to customers) ... biggest problem was that it operated in severe memory constrained environment (by most 370 operating system & application standards). Initial version ... before first customer ship ... was going to go out with only 384kbytes of "370" memory ... which held the resident kernel as well as all paged application code & file. I did some early benchmarks which showed severe page thrashing ... and notice the page file was mapped into a XT 100mills/access hard disk (on a good day, disk was saturated at 10 accesses/second). By the time the first box shipped to customers they got it up to 512kbytes of "370" memory which slighted mitigated some of the problem. -- -- Anne & Lynn Wheeler | lynn@adcomsys.net, lynn@garlic.com http://www.garlic.com/~lynn/ http://www.adcomsys.net/lynn/ ###### From: ignatios@cs.uni-bonn.de (Ignatios Souvatzis) Newsgroups: comp.arch,alt.folklore.computers Subject: Re: IBM XT/370 and AT/370 (was Re: Computer of the century) Date: 6 Jan 2000 15:06:52 GMT Organization: RHRZ - University of Bonn (Germany) Lines: 15 Message-ID: <852b2c$1pe8$1@f1node01.rhrz.uni-bonn.de> References: <84sgc0$mnv$1@mail.ic.uva.nl> <3872047A.73F83228@bellatlantic.ne <84ui3b$gmi$1@nntp6.u.washington.edu> NNTP-Posting-Host: cauchy.cs.uni-bonn.de Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: f1node01.rhrz.uni-bonn.de 947171212 58824 131.220.4.169 (6 Jan 2000 15:06:52 GMT) X-Complaints-To: usenet@f1node01.rhrz.uni-bonn.de NNTP-Posting-Date: 6 Jan 2000 15:06:52 GMT X-Newsreader: knews 0.9.8 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!newsfeeds.belnet.be!news.belnet.be!news-raspail.gip.net!news.gsl.net!gip.net!newsfeed.tli.de!blackbush.xlink.net!rz.uni-karlsruhe.de!news.uni-stuttgart.de!news.rhrz.uni-bonn.de!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:47490 In article , Eric Smith writes: > dpeschel@u.washington.edu (Derek Peschel) writes: >> I trust you but I just want to make sure you didn't make a typo. We're >> talking about the 68000 (by Motorola) plus the 8087 (by Intel)? > > Yes. The 68851 wasn't even close to availability at that time. Make that a 68881. The 68851 is the external MMU for 68020. -is -- * Progress (n.): The process through which Usenet has evolved from smart people in front of dumb terminals to dumb people in front of smart terminals. -- obs@burnout.demon.co.uk (obscurity) ###### Sender: eric@ruckus.brouhaha.com From: Eric Smith Newsgroups: comp.arch,alt.folklore.computers Subject: Re: IBM XT/370 and AT/370 (was Re: Computer of the century) References: <84sgc0$mnv$1@mail.ic.uva.nl> <3872047A.73F83228@bellatlantic.ne <84ui3b$gmi$1@nntp6.u.washington.edu> <852b2c$1pe8$1@f1node01.rhrz.uni-bonn.de> X-Disclaimer: Everything I write is false. Organization: Eric Conspiracy Secret Labs X-Eric-Conspiracy: There is no conspiracy. Date: 06 Jan 2000 15:15:50 -0800 Message-ID: Lines: 8 X-Newsreader: Gnus v5.5/Emacs 20.3 NNTP-Posting-Host: ruckus.brouhaha.com X-Trace: 6 Jan 2000 15:52:45 -0800, ruckus.brouhaha.com Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!enews.sgi.com!news.sgi.com!news.spies.com!ruckus.brouhaha.com Xref: chonsp.franklin.ch alt.folklore.computers:47663 I wrote > Yes. The 68851 wasn't even close to availability at that time. ignatios@cs.uni-bonn.de (Ignatios Souvatzis) writes: > Make that a 68881. The 68851 is the external MMU for 68020. Absolutely right. That's what I meant. Neither one was close to availability at that time.