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From: aaron@jessica.stanford.edu (Aaron Wallace)
Newsgroups: comp.sys.mac.misc,comp.windows.ms
Subject: Re: Mac Vs. Windows? (sorry)
Message-ID: <1991Jun12.152813.20074@leland.Stanford.EDU>
Date: 12 Jun 91 15:28:13 GMT
References: <0E010021.e0mxxc@gla-aux.uucp> <1991Jun4.154854.19649@dbase.A-T.COM> <56nD02AQ08cd01@JUTS.ccc.amdahl.com> <1991Jun12.055711.21457@cs.yale.edu>
Sender: Aaron Wallace
Organization: Academic Information Resources
Lines: 32

In article <1991Jun12.055711.21457@cs.yale.edu> bitting-douglas@cs.yale.edu (Douglas Bitting) writes:
>In article <56nD02AQ08cd01@JUTS.ccc.amdahl.com> kls30@DUTS.ccc.amdahl.com (Kent L. Shephard) writes:
>>>In article Something'er'other, someone wrote:
>>>>2) The Motorola (and for that matter, any linear-addressing processor) is
>>>>faster than segmented memory.
>>
>>Excuse me but this is not the case.  If you have an OS like Unix, System 7
>>or any OS that provide virtual memory you are back to -(drum roll please)
>>a segmented OS.  Pages are just large segments.
>
>Paged != Segmented.  Pages are, by definition, fixed in size.  Segments are, by
>definition, variable in size.  To have fixed page segments defeats the purpose
> [etc...]

>Also, (this is in reply to the quote of the quote of the...) not all Macintosh
>Models are linearly addressed (this is especially true with the introduction of
>VM in System 7).  On some models with the PMMU (the IIci comes to mind), memory
>is not linear even *WITHOUT* virtual memory.  The PMMU makes it look that way
>to software, but it really isn't the case...
>

I've never actually programmed a Mac (life does have it's small blessings!),
but I remember that my girlfriend once had do for a Pascal class.  I remember
her having to worry about arranging static data into segments and getting
segment too large errors.  I've read elsewhere that, lovely as the linear
address space is, Apple went through all kinds of hoops and backflips to
simulate a segmented memory system on the Mac.

Personally, I think segments are great.  64K segments, that's a different 
matter...

Aaron Wallace