Re: Apple//c newbie questions

[spec@vax2.concordia.ca (Mitchell Spector)]

In article gkomatsu@Hawaii.Edu (Galen Tatsuo Komatsu) writes...

>In article <1dgnsti.pylva31yy48u8N@dempson.actrix.gen.nz>,
>David Empson <dempson@actrix.gen.nz> wrote:
>>Galen Tatsuo Komatsu <gkomatsu@Hawaii.Edu> wrote:
>>>       Out of curiosity, where does the third 5.25 get mapped?
>>Mitch said "UniDisk 3.5", which is a different beast.
>>You can only have two 5.25" drives on a IIc, since it has a single disk
>>controller (and thus two drive select signals).  One of them is built
>>into the machine, so you can connect one externally.
>
>       ahem...
>
>-From: spec@vax2.concordia.ca (Mitchell Spector)
>-Date: 8 Oct 1998 05:53 EDT
>-[...] Later versions of the IIc [...] will
>-let you add up to two external 5.25 drives,
>
>       ...not that I'm screaming "you're wrong! you're wrong!  Mitchell
>said two external 5.25s!!!!!!!"  Just defending why I asked my question.

    No, *I* was wrong. When I wrote the above, I wasn't paying
attention and inadvertently described a new feature found only
in the Apple IIc Plus. I noticed that afterwards and corrected
myself in a follow-up.

    David is perfectly correct. With the exception of the IIc+,
all versions of the Apple IIc (ROM 255, 0, 3, 4) only support
one external 5.25 drive, no more. As a rule of thumb, if one
person states one thing and David states another, you can be
almost 100% certain David's answer is the correct one. I wouldn't
hesistate to say he's one of the few people in the world who
knowns the Apple II and its technical aspect as well as (if not
better) than the people who designed all the various incarnations
of the machine. :-)

>Anyway, I was wondering that at the time since my GS has two 3.5s hooked
>up and noticed that /RAM5 pushes one of them over to "slot" 2.

    Well if you hook up two external 5.25 drives on a IIc+ (again,
the only IIc model that supports this) the first one gets mapped
to "Slot 6", Drive 1, while the second to "Slot 6", Drive 2. The
internal 3.5 is mapped to "Slot 5", Drive 1 (and logically, the
second to "Slot 5", Drive 2). The Slinky RAM is mapped to "Slot 4"
and the 64K (bank-switchable) auxiliary RAM, when formatted, "Slot 3"
Drive 2. I don't think anything gets pushed unless you start adding
several extra devices. I'm not even sure the IIc+ allows you to have
both an auxiliary RAM Disk and Slinky RAM disk active at the same
time. In any case, the IIc+ uses '/RAM4', not '/RAM5'.

>>In theory, you could connect 127 UniDisk 3.5 drives to the IIc, as well
>>as one external 5.25" drive (at the end of the chain).
>>In practice, the power supply and signal loading are major restrictions,
>>and the firmware probably has a smaller artificial limit.  The limit
>>would be about four drives in total.
>
>       Where's Tim "The Tool Man" Taylor when your need him...
>More Power! =^)

    Additional power alone wouldn't help, the signal would degrade 
and be too weak after several drives were added (you'd probably
start picking up "noise" too at some point). Anyhow, who still
hooks up a dozen or floppy drives these days? :) (people used to 
run BBSes off system with multiple floppy drives, back when 
hardrives were much too costly to afford).

Mitchell Spector
spec@vax2.concordia.ca