Re: The Apple II is crap

[mjmahon@aol.com (Michael J. Mahon)]

Matthew Russotto replied:

>In article <20030815032734.29543.00000027@mb-m24.aol.com>,
>Michael J. Mahon <mjmahon@aol.com> wrote:
>>
>>The move to 64-bit computing platforms, now starting, is
>>similarly hampered by the entrenched base of 32-bit
>>software.  The ubiquitous "punning" by developers between
>>"integer" and "pointer" is a major obstacle to simple porting
>>of code to a new addressing model, as it was in the past.
>
>Rather difficult to avoid, unfortunately.
>
>>The bad news is that these experiences demonstrate that
>>programmers as a whole do not concern themselves much
>>with the longevity of their code, happily limiting its portability
>>to simplify their lives.
>
>*sigh*.  It all sounds so simple in hindsight, doesn't it?  But using
>the 8 high bits of the pointer to hold flags in 68000 systems saved
>the 16 bits per pointer you'd have had to use to hold them anyway, not
>to mention all the extra fetches you'd need to read and write the
>things.  Portability to future systems is not the only nor even the
>most important criterion programmers are constrained by.

Agreed--there are lots of competitive pressures at work.

This exploitation of the 24-bit address limitation was still taking
place at a time when a "large" physical memory was 4MB-8MB,
or 22-23 bits, only one doubling (or about two years) away from
the 24-bit "limit".  Therefore, whatever good reasons might have
existed, it did not require much foresight to see that this space-
and time-saving trick was about to expire.

-michael

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