Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!gatech!purdue!decwrl!sun!aeras!elxsi!beatnix!rw
From: rw@beatnix.UUCP (Russell Williams)
Newsgroups: comp.arch
Subject: Re: 64 bits
Message-ID: <1723@elxsi.UUCP>
Date: 27 Dec 88 23:47:24 GMT
References: <28200249@mcdurb> <451@babbage.acc.virginia.edu> <1951@scolex>
Sender: news@elxsi.UUCP
Reply-To: rw@beatnix.UUCP (Russell Williams)
Organization: ELXSI Super Computers, San Jose
Lines: 41

In article <1951@scolex> seanf@sco.COM (Sean Fagan) writes:
>> It's long past time that computer systems - compilers and/or
>> ALUs - supported >32 bit integers. 64 bits here we come!
>
>Well, Crays are 64-bit machines, as are Elxsis (nice machine that looks a
>bit like a 64-bit VAX; everybody should buy one 8-)).  Cybers (my favorite

   The Elxsi architecture has very little in common with the VAX except
for a 32 bit virtual address.  The instruction set is not risc, but is
much closer to a risc than to a VAX -- typical cpi for our latest CPU (which
is made out of 2 big boards of ECL) is significantly less than 2.
The registers are 64 bits wide, and 64 bit objects are full citizens.

   Floating-point definitely benefits from this, not just because of fast
64 bit math, but because you can move the items around fast.
The advantages of 64-bit integers are less obvious, though at the lowest
levels it helps because our physical memory addresses are 38 bits wide.

   We went through the same problems other 64 bit folks seem to go through
in porting C programs.  It seems that longs "ought" to be
64 bits, but if they are a lot of code doesn't work;  C wants modulo-2^32
arithmetic even if you're in 64 bit registers, etc.  Word size is another
one of those things like byte ordering -- it's possible to write software
which ports across variations, but it's often ignored when writing 
"portable" software.

   The Elxsi can look like a VAX to software: the FORTRAN compiler accepts VAX
extensions, and various aspects of VMS are emulated to provide source-level
compatibility in many cases (MACRO modules don't run too well...)  Like
the VAX, ports of Unix V.3 and 4.3 BSD are available; unlike the VAX, you
can run all three operating systems simultaneously.

   Nobody wants to look like a VAX, they just want to sell like one.

*****************
My statements do not represent Elxsi's opinions; all copyright and trade mark 
infringements are solely my responsibility.

Russell Williams
..uunet!elxsi!rw
..ucbvax!sun!elxsi!rw