From: David LaFrance-Linden
Subject: Re: Rational for ANSI CL precision?
Date:
Message-ID: <32EF5920.FF6@hpc.pko.dec.com>
David LaFrance-Linden wrote:
>
> Raymond Toy wrote:
> > Were doubles really catastrophically slower on Symbolics? Or is it
> > more an issue that the compiler was not smart enough to unbox it? I
> > might be way off base here because I know nothing about Symbolics
> > architecture.
>
> Both.
> [...]
I wasn't being completely fair. What do you mean by "catastrophically
slower"? Stock hardware, in the absense of declarations, for something
like (+ a b), has to do a two-way type dispatch, and for double
arguments it would likely have to unbox, %double_internal, and box, just
like LispMs. Stock hardware would have to do this all the time in
macrocode, whereas LispMs would do it in microcode with hardware assist.
This made the fixnum and single cases go at machine speed and only trap
for bignums, doubles, rationals, and complex.
Of course, those were the days when the (first) Ivory chip ran around 12
MHz and 16MB of memory (except we called it 4MW) was considered a well
endowed machine...