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From: guy@sun.uucp (Guy Harris)
Newsgroups: net.micro.68k,net.micro.16k
Subject: Re: PDP11s vs the micros
Message-ID: <2506@sun.uucp>
Date: Sun, 28-Jul-85 00:18:21 EDT
Article-I.D.: sun.2506
Posted: Sun Jul 28 00:18:21 1985
Date-Received: Tue, 30-Jul-85 04:49:42 EDT
References: <1617@hao.UUCP> <847@mako.UUCP> <2422@sun.uucp> <2994@nsc.UUCP>
Organization: Sun Microsystems, Inc.
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Xref: linus net.micro.68k:969 net.micro.16k:325

> The 320xx is not a register machine like the PDP11 or some other well
> known processors.  It's a p-machine with some registers added to it for
> extra speed.  You don't expect to have symmetry between the registers
> that make up the p-machine and the other registers that speed it up.

What???  I've read the 32xxx data sheet and the machine looks *far* more
like a "warmed-over VAX" (which is no slur, considering how many machines
out there are just warmed-over PDP-11s or warmed-over VAXes) than a
"p-machine" (by "p-machine" do you mean "p-code engine"?).  Yes, you can use
it as a stack machine (make both operands use the TOS addresing mode) - but
then you can do the *exact same thing* on "the PDP11 (and) some other well
known processors" (such as the VAX).  How many 32xxx instructions use TOS
for both operands, and how many use a register, or register relative/memory
space, or...?  If the majority do NOT use TOS, I submit that the 32xxx is
not a "p-machine" in the sense of an engine intended to run P-code, but
instead a VAXish register machine with some addressing modes added to make
stack-oriented expression evaluation slightly simpler (although, given that
any PDP-11 or VAX instruction with two general-addressing-mode operands can
be made to act like a stack machine instruction, I don't think they even
make it any simpler).

	Guy Harris