Path: utzoo!utgpu!watmath!clyde!att!rutgers!ucsd!sdcsvax!ucsdhub!esosun!seismo!uunet!sco!seanf From: seanf@sco.COM (Sean Fagan) Newsgroups: comp.arch Subject: Re: RISC v. CISC --(really Cyber 170) Message-ID: <1762@scolex> Date: 19 Nov 88 21:53:41 GMT References: <595030314.2944@minster.york.ac.uk> Reply-To: seanf@sco.COM (Sean Fagan) Organization: The Santa Cruz Operation, Inc. Lines: 46 In article <595030314.2944@minster.york.ac.uk> martin@minster.york.ac.uk writes: >In article <1622@scolex> seanf@sco.COM (Sean Fagan) writes: >>where n=[1,5]. To store a value from X, you load the address into A, > ^^^^^ >actually it was n=[3,4,5] A1 and A2 were also general purpose. Nope, sorry. 'SA1 X1' would load the first argument into X1 (assuming you were using FORTRAN calling conventions). Let's hope, however, that you only had one argument 8-). It would, btw, also load the address of the first argument into A1, so that, when you were done, you do: BX6 X1 SA6 A1 and the argument was stored. Nice. (also explains why a 5 can become a 3 and totally screw people up 8-).) >>where n=[6,7]. A0 has no special values, and B0 is a hardwired 0. >> >Note that the Cyber 170 is compatible with the 6600. It was an interesting >machine to program in assembler, as can probably be guessed from the above >description. However PP (Peripheral Processor) programming was much more >fun, since you have unlimited access to the main memory of the Central >Processors - the base/limit memory protection only affected CP programs. >(I'm speaking in the past tense, not because there are no more of these >machines, but because, fortunately, I don't have to program one any more! >I've still got my Compass manuals though!!) True, PP's do (note the present tense 8-)) have unlimited access to the main memory. However, you had to have System Access (or some such) bit set in your Protection word (NOS has, I believe, several 60-bit words for permissions. Many permissions are in the form of one-bit values). Then, you rebuild the libraries (aka the system), and your PP program could be loaded. However: PP's are 12-bit machines, with an Accumulator only. To address any arbitrary word, you a) had to build the address using the P register and the K register (P was 12 bits, K was 6; I think the names are right), and b) had to make five passes, since you only had 12-bit words in the PP. Lastly, why wouldn't you want to program these machines? They are *wonderful*. Anybody who has to learn assembly language should learn these machines (they're about as regular as a PDP, but are much faster, and prepare people for RISC)! -- Sean Eric Fagan | "Engineering without management is *ART*" seanf@sco.UUCP | Jeff Johnson (jeffj@sco) (408) 458-1422 | Any opinions expressed are my own, not my employers'.