Re: [uCsimm] cs8900 & wait-states

From: Tom Walsh (tom@cyberiansoftware.com)
Date: Tue Dec 12 2000 - 22:03:43 EST


 "Florian G. Pflug" wrote:
>
> On Thu, Dec 07, 2000 at 02:10:09PM +0100, sticke_m wrote:
> > There is no reason than just historical of putting the low
> > or the high byte of a word at first in memory.
> > For motorola you can write $12345678 in memory for a $12345678
> > and for intel you write $78563412. It's just a historical reason.
> Hi
>
> Just for interesset...
>
> Does anyone know if it ever had any advantage to do it one or the other way
> round?
>
> The big-endian format seems much more logical to me (after all, $12345678 is
> $12345678 in memory with this).
>
> So there had to be some reason, why someone ever hat the idea to swap the
> bytes and store it as $87654321....
>
> Or, maybe this was just some mistake in an early chip/board layout? ;-))))
> Just like once, long long time ago people actually had an "unmount" command
> - until someone forgot the "n" in an BSD-Release...
>
> greetings, Florian Pflug
> This message resent by the ucsimm@uclinux.com list server http://www.uClinux.com/

I believe that the difference is the attitude toward the way that the
byte stream from memory is regarded, with Motorola the data is regarded
as "services the processor", with Intel the processor "services the
data". If you think about it, forcing data to be in a particular format
(word boundries) is a faster approach, while forcing the processor to
adapt to varing length data / code will likely cause a performance hit.

I know, not clear, but, historically, Intel was always price conscious
and seemed to regard RAM as a costly resource not to be wasted, while
Motorola has always had an attitude of "if you cannot afford it, then
you don't really need our performance edge". Sorry, I have nothing
against Motorola, but they have always gone after the high-end of the
market to the detriment of the low-end. The only time we get cool
embedded stuff to use is when they sell a U.S. automobile manufacturer
on using that chip, after the chip is no longer needed by the auto
people, it usually gets dropped. The only chip that they ever really
kept around was the 68HC11 due to the suprising popularity of the device
in the embedded space (to Motorola's surprise). IMHO, Motorola does not
understand the embedded market, they bumble along and eventually produce
something interesting to the rest of us (DragonBall, 683XX cores).

TomW
 

-- 
Tom Walsh - WN3L - Embedded Systems Consultant
'www.openhardware.net', 'www.cyberiansoftware.com'
"Windows? No thanks, I have work to do..."
This message resent by the ucsimm@uclinux.com list server http://www.uClinux.com/



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