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From: vixie@decwrl.dec.com (Paul Vixie)
Newsgroups: comp.sys.nsc.32k
Subject: Re: most elegant 32-bit design
Message-ID: <20@gnome6.pa.dec.com>
Date: 25 Oct 88 22:34:33 GMT
References: <17@gnome6.pa.dec.com> <981@stiatl.UUCP>
Organization: DEC Western Research Lab
Lines: 49

Somebody asserted that the NS32K was the most elegant 32-bit CPU around.

I said:
# I used to think so, too.  The NEC V70 changed my mind.  CISC heaven.

In article <981@stiatl.UUCP> meo@stiatl.UUCP (Miles O'Neal) writes:
# Not being familiar with the V70, could you expound (just a little, or the ns
# faithful will scream to create a comp.sys.nec.v70) on the features you like
# better about the v70 (vs the 32532) and why?

I don't know much about the 532 -- I am assuming that it has the same 
architecture (in user-mode anyway) as the rest of the 32K series.  I wrote
an assembler for the 32K and own a Symmetric 375 (32016 @10MHz), so I know
the 32K architecture pretty well.  My only real criticism of it are the few
places where its orthogonality falls down: it ought to have double indirection
through any GP register, and it only allows it for the FP/SP type registers;
also, it ought to have auto-increment and auto-decrement.  Otherwise it's
a very neat (as in well-organized and clean) chip.

The V70, on the other hand, has no such fallouts.  It has 32 GP registers,
and like the VAX and NS32K, does not make the silly distinction between
address registers and data registers: a register is a register is a register.
You can use it as a load/store machine and get ~1 clock/instruction on most
register-to-register instructions.  With 32 registers, this almost works.
It has a four-level paging scheme, which is more than U**X needs; the
three-level scheme in the NS32K is enough.  The extra level is easy to
forget about, though, it doesn't get in your face the way the 386 segments do.

There are other interesting features which have all slipped my mind.  I'm not
sure why there are no V70 machines being sold in the U.S.; the first chips
were rated at 20MHz and they should've been screamers.  I've been told that
the V70 is popular in Japan and it will probably be the only competition
against SPARC over there.  Oh, yeah, there is a V60 which has a 16-bit
external data bus but the same internal architecture; something like a 32016
to a 32032.  One last thing: it has a V30 emulation mode; a V30 is basically
an 8086.  Therefore you could run an MSDOS task under UNIX on a V70 without
having the tedium of interpreting all those 8086 instructions.

I think that's about enough.  Call your NEC sales office if you want more
info -- that's what I did, and they sent a whole binder full of specs and
manuals and stuff.

Disclaimer: noone else at DEC knows I'm posting this, unless they read it
the same way you're reading it.  If you must sue somebody over what I've
said here, it'll have to be me, and that would be a waste of your time.
-- 
Paul Vixie
Work:    vixie@decwrl.dec.com    decwrl!vixie    +1 415 853 6600
Play:    paul@vixie.sf.ca.us     vixie!paul      +1 415 864 7013