Re: Prodos driver for > 2 partition on Apple 2e

[dempson@actrix.gen.nz (David Empson)]

David Wilson <mcs6502@gmail.com> wrote:

> > On Apr 5, 2:20 pm, "John" <zzzj...@yahoo.com> wrote:
> >
> > > Is there a Focus friendly 2e driver which would allow more than 2
> > > Prodos partitions?
> 
> I am not sure I understand this question. On an Apple IIe running
> ProDOS, the device driver for any mass storage devices (apart from /
> RAM and Disk ][ drives) is in the ROM on the card they are connected
> to. Support for 4 volumes on a card in slot 5 has been in ProDOS since
> version 1.2 (provided that the ROM code also supports this). If your
> Focus card is in slot 7 then you will be limited to two partitions.

... unless the card in question has implemented the SmartPort firmware
interface, and you are running ProDOS-8 2.0.1 or later. In this case,
ProDOS will allocate the two unit numbers for unused slots (those not
containing other block access devices) to higher numbered drives on
other slots which contain SmartPort firmware.

This works with the IIgs built-in SmartPort (slot 5), also the Apple
SCSI cards and SuperDrive card (in any slot), as well as any third party
card which contains a SmartPort driver.

Another technique is to patch the ProDOS unit table after boot so that
unit numbers for unused slots are mapped directly to the ProDOS block
driver for a different slot. (I think this is how the RamFast SCSI card
operates.) This is only an option if the card's driver has access to its
own private memory which can hold a mapping table to identify how to
associate ProDOS unit numbers with internal drive numbers. This would
typically need a small RAM storage area on the card.

Yet another technique is to install a RAM-based block driver in main
memory, but this is seriously limited because there is no area of memory
which is reserved for this purpose in general use with ProDOS
applications. It may be possible in seriously limited circumstances,
such as if you only use it with BASIC.SYSTEM.

This sort of thing is much easier with GS/OS, which has a proper memory
manager and RAM-based driver architecture.

-- 
David Empson
dempson@actrix.gen.nz