Re: Apple Drops Backward Compatibility for Next MacOS

[nathan@visi.com (Nathan Mates)]

In article <552l5n$cdr@ns1.nl.cis.philips.com>,
Edgar Matzinger <matzingr@iclab.ce.philips.nl> wrote:
>In article <54u5ud$7k6@darla.visi.com>,
>	nathan@visi.com (Nathan Mates) writes:

>  the 640K problem is a hardware limitation. The memory map shows
>these ranges: 0-640K RAM, followed by videoRAM and ROM. If they (IBM)
>had build it the other way around: starting with ROM from 0, followed
>by videoRAM and user RAM, they'd never any problems.

   The x86 has system vectors, etc at memory location absolute 0.
They'd need to put in some weirdly mapped ram to have a few vectors
then the i/o, then the main ram. The 68K series is similar.

   The 65* is kinda rare in having vectors at the top of RAM.

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