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Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!ihlpg!timborn
From: timborn@ihlpg.UUCP (Tim Born)
Newsgroups: net.micro.apple
Subject: bank switching for large memories
Message-ID: <1840@ihlpg.UUCP>
Date: Mon, 21-Apr-86 15:35:12 EST
Article-I.D.: ihlpg.1840
Posted: Mon Apr 21 15:35:12 1986
Date-Received: Wed, 23-Apr-86 14:53:27 EST
Distribution: net
Organization: AT&T Bell Laboratories
Lines: 20

After looking at several memory expansion boards for my Apple ][+, I think I
understand the concept, but I would like more details of how the bank switching
really works.  The 16Kb expansion depends on decoding one of the $Cxxx locations
to determine if the access is for on-board or in-slot RAM.  Why do you 
have to access the location twice?

For the 128Kb expansion, what mechanism is used?  How big are the "chunks"
that are switched?  Are all chunks switched into the same region in the address
spectrum, or can a 16Kb expansion coexist peacefully with a 128Kb expansion?
Can two 128Kb expansions coexist in harmony?  Do the companies that make
the 1 MEG (!) expansions use a different technique?  Has any sort of
standard evolved?  I noticed that some expansion boards need a ribbon cable
connected to the motherboard, others do not.  Why???

If anyone could shed some light on this subject, I would be most grateful.
Would this be of general interest to the rest of the net.micro.apple?

Thanks,
tim born
...ihnp4!ihlpg!timborn