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From: griffith@eecs.cs.pdx.edu (Michael Griffith)
Newsgroups: comp.sys.amiga
Subject: Re: motorola/intel
Message-ID: <69@pdxgate.UUCP>
Date: 11 Sep 90 22:23:32 GMT
References: <30140@nigel.ee.udel.edu>
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thamilton@ch3.intel.com (Tony Hamilton, WF1-81, x48142) writes:

>Isolated I/O.  Each has various advantages and downfalls.  When saying they
>don't compare, I surely hope you infer that they are nothing alike, and not
>that one is better than the other.  The unfortunate thing is that most users
> 
>Defending Intel interests across the globe...
> 
>                    Tony Hamilton
> 
>                 THamilton@ch3.intel.com

It is true that there are advantages and disadvantages to memory mapped I/O
and isolated I/O, but I still must disagree. Motorola chips are better, in
my own opinion (in other words, please no flames. Go ahead and disagree but
please don't get mad.) because of the somewhat higher degree of portability
and the support of the 68000 which enables the upgrade to full 32-bit code
to go so smoothly. The basic register set of the 68000 is still better than
that of the 386 (I don't have full stats on the 486 lying around, so I can't
tell you if that one does), with 8 general purpose data registers and 7
general purpose address registers (although a7 is most commonly used as the
stack pointer the use of a7 or any register as a stack is not strictly
enforced by it). I must say, I feel very hampered when programming assembly
on an 80x86 based machine because of the lack of registers and the strict
rules enforced by the use of segmentation/offset registers and the fact that
the four "general purpose" registers are hardly ever available for general
purpose. However, I don't want to mislead you into thinking I find no fault
with Motorola. The 68000 series has, I believe, around four different
exception frames for the stack. Also, I could have wished for an instruction
which provides chip identification so that it would be a bit easier to
recognize which version of the chip a program is running on. But for power
vs. price vs. performance I think I would always have to pick Motorola over
Intel. (Or rather when forced to choose between the chip series MC68000 and
i80x86.)


| Michael Griffith                     | If I had an opinion it certainly   |
| griffith@eecs.ee.pdx.edu             | wouldn't be the same one as        |
| ...!tektronix!psueea!eecs!griffith   | Portland State University anyways. |