Path: utzoo!attcan!uunet!munnari!moncskermit!goanna!yabbie!gecko!rcorf From: rcorf@gecko.co.rmit.oz (Roy Ferguson) Newsgroups: comp.arch Subject: Re: History of personal computing (LONG) Message-ID: <287@gecko.co.rmit.oz> Date: 4 Aug 88 09:14:27 GMT References: Organization: RMIT Comm & Elec Eng, Melbourne, Australia. Lines: 46 From article , by andrew@jung.harlqn.uucp (Andrew Watson): > > You'll find copies of several seminal (good word, that) papers of relevance > in "Computer Structures: Principles & Examples", Siewiorek et al, McGraw-Hill > (all this from memory, so I may not have the title quite right). This > collection of reprints includes the Ethernet paper, the Alto paper and others > (including Wilkes' *original* microprogramming paper!), and is a happy hunting > ground for architectural archeologists like me. > > On a more-or-less related note, the above-mentioned book contains plenty of > material on the PDP-8 and -11, but nothing on the DG Nova, which I'm told was > quite interesting, architecturally. Can anyone help me out with pointers to > information on this? C. Gordon Bell, one of the authors of the original version of "Computer Structures ..." was associated with DEC. Now DEC do not appear to ever acknowledge the existence of DG as DG's founder, Edson DeCastro, was a former DEC engineer on the PDP-5 and PDP-8. In the book "Computer Engineering: A DEC view of hardware systems design" by Bell, Mudge & McNamara, Digital Press 1978, Edson DeCastro's name is mentioned just once. I think that explains why the Nova is not mentioned in "Computer Structures ...". Actually I have a copy of the first version of "Computer Structures ..." published in 1971 and that only has the PDP-8 and not the PDP-11. In fact the DG Nova was a 16-bit version of a 12-bit machine (the PDP-8) and architecturally is atrocious compared to the PDP-11 at least in my opinion. It has been a long time since I programmed a Nova, but it had only 4 registers and NO stack push or POP instructions. My memory is very rusty but I recall that interrupts always jumped to the location at address 0, there were 16 memory addresses in page 0 that were special, 8 were autoincrement and 8 autodecrement. It had the curious feature that on an indirect memory access if the high bit of the address was set it would treat that as another level of indirection and it would keep doing that until it found an address without the high bit set. Of course it could only address 16 bit words (NO byte addressing) so special coding was required to access a string of characters stored two to the word. Note that it still only had 32kword address space (allowing it to use the high bit for indirection as noted above). I suppose you could say it was interesting but you wouldn't want to program it in assembly language. Roy Ferguson, Dept. Communication & Electrical Eng., Royal Melbourne Institute of Technology.