Re: IIgs 3.5" disk drive limit

[hlevinsn@rci.rutgers.edu (Hank Levinson)]

dempson@actrix.gen.nz (David Empson) writes:

>Dennis Jenkins <dennis@usb.com> wrote:

>> How many 3.5" and 5.25" drives can I daisy chain together on a ROM01
>> IIgs?  I assume that I can have no more than 2 5.25" drives.  How many
>> 3.5" drives can I have?

>There are sevearl limits to consider:

>1. The number of drives of each type which can be addressed using a
>single disk controller.  (There may also be a software limit on the
>total number of drives which may be connected, no matter what type they
>are.)

>2. The signal loading restrictions, which determine the maximum number
>of drives of all types which may be connected to a single disk
>controller.

>3. The power supply loading restrictions, which determine the maximum
>number of drives which may be connected to the entire computer.

>4. The operating system may impose a limit on the total number of
>drives/volumes.  For example, ProDOS cannot access more than 14 volumes.

>Unfortunately the signal and power supply limits are not always well
>defined.

>The addressing limits for floppy drives are easy:

>- There is a limit of two 5.25" drives on any one controller.

>- There is a limit of two Apple 3.5 Drives (or equivalent, such as
>  SuperDrive) on any one controller.

>- There is a theoretical limit of 127 UniDisk 3.5 drives (or other
>  intelligent SmartPort devices) on any one controller.

>The signal loading restrictions generally restrict you to four drives
>per controller, though it may be possible to connect more in some cases.

>The power supply loading restrictions vary between computers.  If you
>had a heavy duty power supply, you could probably fill all seven slots
>of an Apple ][, and have two drives connected to each.

>> My current system has 2 of each, with the following slot assignments:
>> 
>> slot 1)  Apple SCSI Card.  D1 = /HD (32M drive) D2 = nothing
>> slot 2)  onboard serial   D1 = 2nd 3.5" drive
>> slot 3)  D2 = /RAM
>> slot 4)  onboard mouse
>> slot 5)  onboard smartport  D1= 1st 3.5" drive, D2 = /RAM5
>> slot 6)  onboard floppy  D1/D2 = 5.25" drives.
>> slot 7)  onboard appletalk
>> 
>> If I add a thrid 3.5" drive, and it works, will it become S2D2?

>You could connect a UniDisk 3.5 to your built-in disk port (after the
>Apple 3.5 Drives and before the 5.25" drives), as long as it didn't
>exceed the signal loading and power supply restrictions.  This would
>become S2,D2.

>You cannot connect a third Apple 3.5 Drive, because the hardware can
>only address two of them on a single controller.

>You could also add another disk controller card (at the expense of one
>of your built-in ports) and connect two Apple 3.5 Drives to that.

One could use drives, controllers and cards made by Rana. They allow four 5.25"
drives per card: D1,D2,D3,D4 on one card and slot. Rana drives are bulkier
than Apple drives, and Rana DOS is touchier than DOS 3.3.

A heavy duty power supply can be made from an IBM power supply. Steve Buggie
(Buggie@unm.edu) makes them for the AppleGS.

Rana drives are occionally found on ebay.

Good luck!