Subject: Re: IIc hard drive hack?
From: dempson@actrix.gen.nz (David Empson)
Date: Wed, Sep 16, 1998 7282
Message-id: <1dfha0t.hjo1c8li93pcN@dempson.actrix.gen.nz>

TWS <adoyson@nccn.net> wrote:

> The Apple IIe, IIc and IIc+ all use the same
> technology, don't they?
> 
> On the IIc and +, the motherboards are built
> without slot connectors. Aren't the same
> signals used on the IIc for 5.25 drive access,
> serial access, etc?

Some of the same signals are used, but several critical ones are
missing.

In particular, the IIc has no support for separately addressable
firmware areas for each slot.  All "slot firmware" is part of the main
motherboard ROM.

In addition, the IIc doesn't support the 2K bankswitched area at
$C800-$CFFF.  It is permanently used by the 80-column firmware.

Trying to hack a card into a IIc would at the minimum require rerouting
several address lines through address decoding circuitry to identify
address ranges for the slots in question.

The IIc also doesn't generate the DEVSEL signals (16 byte I/O window for
each slot) in the same way.  The MMU and GLU chips generate specific
select lines for each chip that requires addressing in these areas (the
two 6551 ACIAs and the IWM).

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand