NetNews Usenet Archive 1992 #20/NN_1992_20.iso/spool/comp/arch/9336

Internet Message Format | 1992-09-09 | 2.7 KB

Path: sparky!uunet!spool.mu.edu!sol.ctr.columbia.edu!ira.uka.de!uka!uka!news
From: [e-mail] (|S| Norbert Juffa)
Newsgroups: comp.arch
Subject: Re: Intel CAD coprocessor?
Date: 10 Sep 1992 17:24:36 GMT
Organization: University of Karlsruhe (FRG) - Informatik Rechnerabt.
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Message-ID: <[e-mail]>
References: <[e-mail]> <[e-mail]>
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In-Reply-To: [e-mail]'s message of 9 Sep 92 19:22:42 GMT

In <[e-mail]> [e-mail] writes:

> The Intel RapidCAD processor chipset is a replacement for the 386DX/387DX chipset.
> The DX is the operative word here: DX's (from Intel, anyway) are PGA devices
> which are usually socketed.
>
> I haven't used one yet so I can't make any comments on Intel's claimed performance
> gains. If you have a 386 machine it is an alternative to upgrading to a 486,
> however, these days, upgrading to the 486 is not a whole lot more expensive
> (if you can migrate your memory to the new machine, that is). The RapidCAD
> is not as fast as the 486.
>
> Hope this helps...
>
I actually own one of those beasties. The RapidCAD is basically a 486DX without
the internal cache and with a 386 pinout. It is divided into two chips. The
first one, RapidCAD-1 contains the complete CPU+FPU and goes into the 386
socket. The second one, RapidCAD-2, is just a small PLA that generates the
Ferr signal that normally goes from a coprocessor thru the motherboard logic
(chip set) to the CPU. Floating point performance is about 70-80% of a 486DX
at the same clock speed, if you have a cache installed (I have 128 kB CPU
cache). Compared with a 386/387 combination, RapidCAD is about twice as fast
as the fastest 387 'clones'. Integer performance is about 5-35% higher (15%
average) than with a 386. The slow memory interface of the 386 and the absence
of an internal cache is a bottleneck that prevents the integer performance to
be higher. As pointed out before, the RapidCAD is usually not cost effective
compared to a 486 motherboard. However, some people may be unable to upgrade
to 486 board for various reasons, and for these RapidCAD provides the highest
performance you can get with a 386 motherboard. It also eliminates the need
for a Weitek coprocessor, as the RapidCAD provides the same level of
performance, but is supported by much more programs, since to software it looks
just like a 386/387 combination.

Norbert
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Norbert Juffa       email: [e-mail]        Live and let live!