Re: Apple Drops Backward Compatibility for Next MacOS

[crobato@kuentos.guam.net]

In <5536k4$qr6@client2.news.psi.net>, smentzer@pacbell.net (Steve Mentzer) writes:
>In article <552l5n$cdr@ns1.nl.cis.philips.com>, matzingr@iclab.ce.philips.nl 
>says...
>>
>>In article <54u5ud$7k6@darla.visi.com>,
>>        nathan@visi.com (Nathan Mates) writes:
>>> 
>>>    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,... 8<
>>
>>Hi,
>>
>>  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.
>>
>>
>
>
>
>Not necessarily.  Yes, the 8086 and 8088 had a "segmented" memory architecture
>that limited addressing to 640k. But with the advent of the 286 and higher, 
>additional "modes" were implemented allowing linear memory addressing.
>
>The only reason DOS still runs on the newer chips is because of its 
>"backwards" compatibility. In fact, when you are running dos, you are 
>really running a super-fast, cached, 8086.
>
>smentzer@pacbell.net
>

You are a little off in the X86 generational features.  The 286 still featured 
a pure segmented memory architecture; it was the 386 that first offered linear 
memory addressing.

Rgds,

Chris



Demonically possessed Lisa:  "I am the essence of all the is evil in the computer world."
Gary:  "Are you Bill Gates?"   
						---- from the TV series, Weird Science.

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