Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!uwvax!astroatc!johnw From: johnw@astroatc.UUCP (John F. Wardale) Newsgroups: comp.arch Subject: Re: 360 vs Vax stuff Message-ID: <430@astroatc.UUCP> Date: Wed, 2-Sep-87 23:12:27 EDT Article-I.D.: astroatc.430 Posted: Wed Sep 2 23:12:27 1987 Date-Received: Sat, 5-Sep-87 10:06:12 EDT Reply-To: johnw@astroatc.UUCP (John F. Wardale) Organization: Astronautics Technology Cntr, Madison, WI Lines: 84 Keywords: Vax-bashing Summary: Replies to stuff from last week I while ago I made the following claims about pipelining in regards to 360's and VAXen, which generated some warm replies. I should have answered them sooner, but the best laid plans of mice and men.... >From: petolino%joe@Sun.COM (Joe Petolino) me> The 8600 overlaps operand-decode with operand-fetch, and uses me> multiple functional (execution) units, but **UNLIKE** IBM and any me> other true pipe-line design, can *NOT* have multiple instructions me> in the decode phase simultaniously! > > This is certainly a novel criterion for calling a design 'pipelined'! > All of the CPU designs I know of (this includes machines by IBM, Amdahl, > MIPS, and Sun) have at most one instruction in each pipeline stage at any one Very true, but a phase is not a state [see below] > second-guessing deleted...also see below >From: bcase@apple.UUCP (Brian Case) > In article .... [I wrote] me> THE *MAJOR* me> reason the ancint 360/370 stuff is still alive, while DEC's vaxen me> are falling by the wayside (despite DEC's best efforts) is that me> 360's *CAN* be pipelined (tho not necessarily real easily) and me> VAXen can't! > > I beg your pardon, but your statement is quite a bit stronger than reality > will permit. I, for one, believe that the high-end VAXs are quite pipelined. Mmmm...Not really. me> The 1st byte of each 370 instruction tells the length of the instruction! > > You have pin-pointed one of the VAX's problems. This does not prevent, > absolutely, pipelining. Ok, but it ties the designers hands and one foot behind his back!!! ---------------------------- First I will admit that my phrasing WAS not great...(That's why I'm trying to clearity... By "decode phase" I'm refering to anything *BEFORE* the instruction is issued. By *MY* definition (which could be totally off the wall) a machine that can only work on cracking (opcode-decode, operand-decode(VM?), operand-fetch, hazard-checking, etc.) is NOT pipelined. [if you declare one "cracking" and two being "executed" as "pipelined" that's OK, but I'm talking about *REAL* assmbly-line pipelining ] ---------------------------- >From: guy%gorodish@Sun.COM (Guy Harris) asks: > OK, so if you implement a VAX using the same technology as a top-of-the line > IBM mainframe, how fast would it be? > [ top of the line speeds ] do not *in and of itself* indicate that > this is due solely to architectural problems with the VAX. Theoreticly true, but in this case, I think it is. I believe the encoding of VAX instructions prevents one from making it go fast, while still being affordable. (Its a point-of-diminishing returns question.) Comments...Anyone think it'd be (economically) worth building a VAX 3X or 10X the current top-vax? Or has it [as I feel it has] reached the limit for current technology. Have 360-type machine speeds been improving with, or faster than technology-speeds? (sorry if that's too vague) What is the rate or rates of top-360 speed increase, and how does this track technology speeds?? s | e | ==/ e | ==/ ==/ d | ==/ ==/ upper line is tecnology limit | =/ lower line is 360 limit | / | / question: is the 360 in the /, the =/ or | / the ==/ part of its line. (i.e. | / I don't know where dates are on ------------------- the time line.) time crt grafix suck....lets all buy Mac-II's (semi :-) -- John Wardale ... {seismo | harvard | ihnp4} ! {uwvax | cs.wisc.edu} ! astroatc!johnw To err is human, to really foul up world news requires the net!