Re: Apple Drops Backward Compatibility for Next MacOS

[nathan@visi.com (Nathan Mates)]

In article <54u3u0$285u@uni.library.ucla.edu>,
 <pubpc1@library.ucla.edu> wrote:
>But: the Apple IIGS has a 16-bit CPU with a 24-bit memory address.
>     the IBM PC/AT has a 16-bit CPU with a 24-bit memory address.

>Both computer can take up to 8MB of memory on a card.  The AT had
>a 640K problem, though.  The GS did not.

   That 640K problem is a limitation of MS-DOG. With the 286 series of
chips that could easily address 1MB of ram, Mickeysoft had a perfect
opportunity to shatter the 640K barrier, letting programs use RAM as
much RAM as they could on the machine. However, in putting the
"backward" in backward compatability, they decided to cripple DOS on
the 286, the 386, the 486, the Pentium, and the Pentium Pro. STUPID
move. You can break a few things once that assume 640K only, or you
can cause enough headaches for the next 15+ years to get a subsidy from
Tylenol.

   [The GS could have continued to use the bank-switched memory of the
//e's AUX expansion slot, for a comparable example. Thankfully,
Apple's designers had their heads on straight, unlike the marketing
dept.]

Nathan Mates

--
<*> Nathan Mates http://www.visi.com/~nathan/      <*>
# What are the facts? Again and again and again-- what are the _facts_?
# Shun wishful thinking, avoid opinion, care not what the neighbors
# think-- what are the facts, and to how many decimal places?  -R.A. Heinlein