billa@ihlpl.ATT.COM (Anderson) (10/13/87)
From ihnp4!homxb!mtuxo!mtune!rutgers!sri-spam!ames!amdcad!sun!pitstop!sundc!seismo!uunet!mnetor!utgpu!dennis Sun Oct 11 15:36:17 1987 Path: ihlpl!ihnp4!homxb!mtuxo!mtune!rutgers!sri-spam!ames!amdcad!sun!pitstop!sundc!seismo!uunet!mnetor!utgpu!dennis From: dennis@gpu.utcs.toronto.edu (Dennis Ferguson) Newsgroups: comp.arch,comp.unix.wizards,comp.os.minix Subject: Re: pdp-11/55 Summary: Chronology not quite correct Message-ID: <1987Oct11.163617.1192@gpu.utcs.toronto.edu> Date: 11 Oct 87 20:36:17 GMT References: <1755@ncr-sd.SanDiego.NCR.COM> <275@usl> <29933@sun.uucp> <2949@phri.UUCP> <1806@gryphon.CTS.COM> <3019@ames.arpa> <72@bacchus.DEC.COM> <89@piring.cwi.nl> Reply-To: dennis@gpu.utcs.toronto.edu (Dennis Ferguson) Organization: Mechanical Engineering, University of Toronto Lines: 44 Checksum: 30538 In article <89@piring.cwi.nl> jack@cwi.nl (Jack Jansen) writes: > >I'll tell what I know, in roughly chronological order. [...] > 11/780 First VAX. Basically an 11/04 with an extra 32 > bit processor and lots of extra busses. Also slightly > more expensive. > 11/03 LSI version of 11/04. First Q-bus machine. The Q-bus > is a poor-mans-unibus: multiplexed A/D lines, only > one level of interrupts, etc. The chronology is quite rough here. I think the 11/03 might have been available as early as 1973 or 1974. I definitely saw my first one in 1976, a year or two before 11/780's were sold (indeed, the console subsystems in 11/780's include an 11/03). I remember this well, that 11/03 was the first computer I ever wanted to take home. I eventually did, but much later, I use the CPU as a paper weight. The Q-bus had 4 interrupt request lines from the beginning, like the Unibus, though the 11/03 only supported one level. The Q-bus did (and still does) only have one daisy-chained interrupt acknowledge line, however. I think the latter is the reason why the microVax always sets the processor priority to spl7() when servicing an interrupt (and why the clock on early Ultrixes loses time) no matter what the bus priority of the requesting device is. You can't tell for sure what the priority of the device which ends up taking the interrupt is. > 11/23 LSI version of 11/34 with Q-bus. But with 22 bit addressing. I remember cutting traces on old peripheral cards which used a couple of the new address lines as grounds so I could run an 11/23 in 22 bit mode and use the extra memory as a RAM disk for RT-11. > 11/74 LSI version of 11/70, with qbus. I think this is really an 11/73. And it probably wasn't exactly like an 11/70, it took years before DEC software would actually let you run a separate I/D space program, even through the same OS would do this fine on an 11/70. -- Dennis Ferguson Mechanical Engineering University of Toronto This guy needs to learn which news group to post to as well!