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From: kateley@apple.UUCP (Jim Kateley)
Newsgroups: comp.sys.mac
Subject: Re: Virtual Memory with the Mac OS
Message-ID: <6416@apple.UUCP>
Date: Mon, 5-Oct-87 21:08:05 EDT
Article-I.D.: apple.6416
Posted: Mon Oct  5 21:08:05 1987
Date-Received: Fri, 9-Oct-87 04:48:22 EDT
References: <2653@okstate.UUCP> <2542@batcomputer.tn.cornell.edu>
Reply-To: kateley@apple.UUCP (Jim Kateley)
Organization: Apple Computer Inc., Cupertino, USA
Lines: 26
Keywords: virtual memory 68851

In article <2542@batcomputer.tn.cornell.edu> chow@tcgould.tn.cornell.edu (Christopher Chow) writes:
>In article <2653@okstate.UUCP> norman@a.cs.okstate.edu (Norman Graham) writes:
>>Does anyone out there know what it would take to have demand paging virtual 
>>memory on the Mac II?  Could it be as simple as plugging in a 68851 and 
                                                                ^^^^^
>One thing which you might want to question is whether if you want to add an
>68851 MMU to your Mac II.  I'm not a hardware guru, but from what
>understand, the 68851 chip adds wait state(s) to every memory reference.
                                 ^^^^

As I understand it, there is currently a wait state for the HMMU anyway,
so adding the 68851 will not add another.  According the the Macintosh
family hardware reference, there are 5 clock cycles in a RAM/ROM access.


-- 

Jim Kateley
Applelink: kateley1
UUCP: {sun, voder, nsc} apple!kateley
CSNET: kateley@apple.COM

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