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Yes, they are special, but...
Date: Fri, 9 Jun 89 12:22 EDT
From: barmar@Think.COM (Barry Margolin)
Date: Fri, 9 Jun 89 09:16 CDT
From: email@example.com (William D. Gooch)
...."highly specialized hardware"....
I've heard this idea bandied about enough that I suppose I should
understand it by now, but - sorry if I'm being dense - I still don't
know what it means. The term "specialized," usually stated as in
opposition to "general-purpose," implies that there are things one
cannot do on a Symbolics machine which other hardware does support.
If you don't mind my asking, what are those things?
It's not that Symbolics machines can't do things that other machines
can, it's that they don't do many common things well. Symbolics
machines are optimized for Lisp processing, and perform poorly at just
about everything else. I/O performance is abysmal.
The poor I/O performance of Genera has little or nothing to do with the
hardware architecture. There has simply never been any serious effort
expended to make paging and I/O fast. The homogeneous address space
makes the paging problems tougher to solve, but the schemes we have
conceived have never been implemented.
It doesn't matter
how fast you can do generic arithmetic if the machine grinds to a crawl
when it pages. They claim that they run C code at about the same speed
as a Vax 11/750; meanwhile, Sun-4 users have desktop machines that get
at least 5 times that performance for a fraction of the cost. The Suns
even beat the pants off them in Lisp processing; our code runs in both
Genera and Lucid, and compiles and loads several times faster in Lucid.
Note that in the above comparisons, the Symbolics machines are 3600
series, not Ivory machines. I don't know whether they've improved the
I/O performance in the XL400.
I love my Lispm, and won't give it up. It's a great hacker workstation,
and I love poking around in Genera. But to be called "general purpose",
a machine has to perform reasonably at lots of different tasks, and
these machines don't.
I disagree. Symbolics machines perform reasonably well at a lot of
different tasks. Some of the tasks it does not perform well at are
important, but that does not make our hardware "special purpose".
BTW, I agre with all your criticisms, but not your final conclusion.