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From: bcase@apple.UUCP (Brian Case)
Newsgroups: comp.arch
Subject: Re: The 360 was a design landmark  (360 vs vax)
Message-ID: <4644@apple.UUCP>
Date: Thu, 27-Aug-87 13:17:59 EDT
Article-I.D.: apple.4644
Posted: Thu Aug 27 13:17:59 1987
Date-Received: Sat, 29-Aug-87 11:53:23 EDT
References: <855@tjalk.cs.vu.nl> <2683@hoptoad.uucp> <916@haddock.ISC.COM> <418@astroatc.UUCP> <26444@sun.uucp> <2595@ames.arpa>
Reply-To: bcase@apple.UUCP (Brian Case)
Organization: Apple Computer Inc., Cupertino, USA
Lines: 49

In article <2595@ames.arpa> lamaster@ames.UUCP (Hugh LaMaster) writes:
>Only very limited pipelining is possible with the VAX architecture.  It is
>just about the worst in that respect of any major computer architecture.  In

It is bad, but it is possible to brute-force pattern-match the most common
instructions; this is expensive in hardware, but it can be done; I don't know
if this is being done in the 86/87 series machines.  I suspect Motorola will
have to resort to the same techniques DEC is using for faster 680x0 machines.
Depending upon the how much you are willing to pay, you get an implementation
where some things run at one-per-cycle, while other things take their usual,
sweet time.

>fact, it seems to have been a reaction to the VAX which brought about the
>revival of ultra-pure RISC machines (RISC concepts had been in use all along
>on some other machines, e.g. CDC).  As was previously noted, a good compiler

Ultra-pure RISC machines were originally motivated by a brillian recognition
of the synergy between compiler considerations and hardware considerations.
At least this is my impression from reading the literature.

>can produce rather dense code for the VAX.  The 64,000 MIPS question is: how
>important is that?  Was it ever that important?  If memory utilization was
>that important even in 1977, why didn't the paging hardware support direct

Well, just read one of Wirth's most recent papers; at least at the time of
that writing, he seemed to think it was the *only* metric!

>LRU?  DEC's success with the VAX was due to the 32 bit virtual memory
>environment- a first for minicomputers at the time- not performance or
>price/performance.
>
>I would second the statements of many previous posters that the 360
>architecture has proven to be very versatile, and has certainly been
>implemented over a wider range of hardware complexity and performance than any
>other architecture.  Too bad about that MVS stuff...

True, true, true, but, at least from a purist point of view, and this is a
news group for computer architecture, not admirable marketing/engineering
trade-offs, it leaves much to be desired.  Throw enough resources at an
architecture (within reason), and you will get a fast implementation.  This
does not mean that the 360/370 is any more versatile than other stuff!  My
comments do not, however, diminish the well-taken point of the earlier-made
statement "May your favorite architecture be as successful in 25 years as
the 370 is now."

>			"IBM will have it soon"

Unless by "have" you mean "own," don't count on it.  Or perhaps, "No, they
already have it, but it'll never see the light of day."