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From: toddpw@tybalt.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.sys.apple2
Subject: Re: Need a little help or a few suggestions...
Message-ID: <1990Oct16.071841.26646@nntp-server.caltech.edu>
Date: 16 Oct 90 07:18:41 GMT
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First, the reason for the two drive limit is in prodos itself. Published
specs for prodos are such that only two drives may be associated with each
slot, period. Apple gets around this by mapping the next two into another
slot so that prodos thinks there are two drives in one slot and two in
another -- some programs still break but Apple documented it pretty well
so there haven't been too many problems.

I forget _why_ it only works in slot 5, but in any case SCSIPART will solve
things by manually mapping the extra partitions into slot 1 drives 1 and 2.

SCSIPART will soon be available for anonymous ftp, I will post an announcement
in a few days giving the details.

As for your 'extender box' idea, most cards are designed to apple's guidelines
and rely on only these signals as master enables:

pin	name
1	IOSEL
20	IOSTRB
39	M2SEL (only in the GS)
41	DEVSEL

so for a //e box you only need to switch 3 lines -- assuming the cards are
designed properly. In general, if it works in both the GS and the //e, then
it uses IOSEL, IOSTRB, and DEVSEL. The only card I know of that pays any
attention at all to M2SEL is the Video Overlay Card.

All the other pins (except DMA IN/OUT and INT IN/OUT, which you will want to
leave unconnected) are identical on all slots as far as you are concerned.

Todd Whitesel
toddpw @ tybalt.caltech.edu