Newsgroups: comp.sys.amiga.tech
Path: utzoo!utgpu!watserv1!maytag!watdragon!tiger!gpsteffler
From: gpsteffler@tiger.uwaterloo.ca (Glenn Steffler)
Subject: Re: MC68881/2 Support (hello, Dave Haynie)
Message-ID: <1990May31.025529.28370@watdragon.waterloo.edu>
Sender: daemon@watdragon.waterloo.edu (Owner of Many System Processes)
Organization: University of Waterloo
References: <1181@metaphor.Metaphor.COM>
Date: Thu, 31 May 90 02:55:29 GMT
Lines: 49

In article <1181@metaphor.Metaphor.COM> djh@dragon.metaphor.com (Dallas J. Hodgson) writes:
>
>Since the FFP instructions trap out thru the FLINE vector anyway (if there's
>no coprocessor present) why don't we EMULATE a 6888x when the traps occur?

I am not sure about the 680x0 line of processors, but the 80x86 line
definately slow down when a lot of coprocessor traps occur.  The best
way to do it (IMNSHO) would be to place code in the program which calls
the floating point library function.  If a coprocessor is available, the
library runtime link code would replace the library calls with actual floating
point processor instructions (like, fix up the code man).

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Attention Hazy:

Does the Amiga handle faults, and other hardware interrupts faster than
a generic PC?  I know the 80386 is very slow when interrupts start
wailing away in protect mode.
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(Microsoft Windows 3.0 math libraries are available which do this, and
 in fact i beleive Microsoft Excel uses them)

>Put this support in the RKM, and let all the compilers generate in-line FFP
>instructions. Yes, there's a small amount of overhead for non-FFP users, but

Like I said, WAY TO MUCH OVERHEAD...

>it's no different from the PC way of doing things - and very
>system-friendly! Let's say GOODBYE to the math libraries; if a user wants to
>install a Weitek in the future, the vendor(s) can supply the driver software
>themselves - and everything will still work.

Not necessarily the way the PC does it...
>
>Just a thought.
>+----------------------------------------------------------------------------+
>| Dallas J. Hodgson               |     "This here's the wattle,             |
>| Metaphor Computer Systems       |      It's the emblem of our land.        |
>| Mountain View, Ca.              |      You can put it in a bottle,         |
>| USENET : djh@metaphor.com       |      You can hold it in your hand."      |
>+============================================================================+
>| "The views I express are my own, and not necessarily those of my employer" |
>+----------------------------------------------------------------------------+

Just a reply.

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Co-Op Scum