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From: andy@rocky.UUCP
Newsgroups: comp.arch
Subject: Runtime checks
Message-ID: <771@rocky.STANFORD.EDU>
Date: Thu, 19-Nov-87 19:19:02 EST
Article-I.D.: rocky.771
Posted: Thu Nov 19 19:19:02 1987
Date-Received: Sat, 21-Nov-87 18:28:04 EST
References: <1656@geac.UUCP> <863@winchester.UUCP> <197@m2.mfci.UUCP> <6743@apple.UUCP> <931@gumby.UUCP>
Reply-To: andy@rocky.UUCP (Andy Freeman)
Organization: Stanford University Computer Science Department
Lines: 28
Keywords: Lisp machines do it

In article <6743@apple.UUCP>, bcase@apple.UUCP (Brian Case) writes:
> I am not trying to pigeon-hole people or sound negative in any
> way, but in general, I find that Europeans tend to have a real sympathy
> for run-time checking.  I can't name one American, off the top of my
> head, to whom I would attribute the same concern.  At least the concern
> would not, to me, be the distinguishing feature that, to me, it so often
> is in Europeans.

Lisp machines (MIT style, as in Symbolics and LMI, and I think Xerox
D-machines as well) all have run-time checking for things like integer
overflow, can a specific pointer operation be performed with a given
value, etc.  As Tom Knight (Symbolics and MIT in the CADR days) says:

"The addition of small amounts of special purpose hardware to conventional
machines increases the efficiency of Lisp systems with dynamic type checks."

I think SPARC has some support for tags.  Patterson has mentioned
similar things, but I don't remember whether they made it into
RISC-II.

Didn't Burroughs use hardware for tag checking too?

-andy
-- 
Andy Freeman
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