Path: utzoo!attcan!uunet!know!samsung!munnari.oz.au!uniwa!DIALix!bernie
From: bernie@DIALix.UUCP (Bernd Felsche)
Newsgroups: comp.sys.amiga
Subject: Re: motorola/intel
Summary: What, no I/O specific 680x0 instructions?
Keywords: Instruction set, memory-mapped I/O
Message-ID: <566@DIALix.UUCP>
Date: 15 Sep 90 04:22:54 GMT
Expires: 30 Sep 90 00:00:00 GMT
References: <30140@nigel.ee.udel.edu> <14427@cbmvax.commodore.com>
Reply-To: bernie@DIALix.oz.au (Bernd Felsche)
Organization: DIALix Services, Perth Western Australia
Lines: 36

In article <14427@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes:
>
>As Larry has said here, it is impossible to both understand and appreciate
>the Intel architecture.
>
ditto

[quote deleted]
>
>You're missing the point.  First of all, dedicated I/O instructions are an
>extremely archaic concept.  I imagine the only reason they existed on the 
>8088 in the first place was because the 8088 was designed to be relatively
>close to assembly-source level compatible with 8080/8085 machines.  The use
>of this technique in the 8080 was mainly to get around address space limits
>(you could have 64K AND I/O devices at once), but it's a horrible waste of
>instruction decoding, and the rest of the world does fine without it.

But, but what about the 680x0's MOVEP instruction?  It exists to
support the older 6800 chips.  And presumably consumes some
instruction decoding.

I know that "nobody" uses it, but it is there.  Or wouldn't you
class it as an I/O instruction?  Agreed, it is not I/O mapped. but
it *is* a special I/O instruction.

>-- 
>Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
>   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
>      Get that coffee outta my face, put a Margarita in its place!

If we were all perfect, the world would be extremely boring.

bernie

| bernie@DIALix.oz.au
| I don't sign anything until I see the money. :-)