Re: Help w/][+ & Prodos

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

In article <42q8tj$364@aplinfo.jhuapl.edu>,
Robert Jensen  <bob_jensen@jhuapl.edu> wrote:
> 
> I have a II+ and have been running ProDOS up through version 2.0.3
> (with a 65c02 installed). I have only been able to make things work
> with a 16k board in slot 0. I tried a 1 meg ram board in slot 0 and
> got relocation/configuration errors. The board is good and has been
> used as a ram disk and as Appleworks memory.

I assume this is an Apple II Memory Expansion Card (Apple's 1MB card),
or a clone such as a RamFactor?  This type of card is nicknamed a
"slinky" RAM card.

This type of card is in no way compatible with a language card.
ProDOS requires a language card in slot 0 on a II+.

There were some third-party RAM cards that implemented a multi-bank
language card.  These should work with ProDOS, provided that only the
first 16K was used (or programs used the rest directly, being very
careful with bankswitching).


A 16K language card provides 12K of directly addressable memory, which
is switched into memory in place of the motherboard ROM at $D000 to
$FFFF, using the INHIBIT signal on the slot.  There are two 4K banks
at $D000 to $DFFF.  Soft-switches at $C080-$C083 and $C088-$C08B are
used to select whether the language card or ROM is being read from,
whether the language card is write-enabled, and which of the two banks
at $D000 is available.

ROM cards such as the Integer and Applesoft cards work in a similar
way, but don't provide the second 4K bank or write capability.

A language card can be used in any slot, but most software expects it
to be in slot 0.  It is possible to install multiple language cards
and/or ROM cards, but only one of them may be enabled at a time (two
or more cards enabled at once would try to drive the data bus at the
same time, which is likely to cause a crash, or at least increase
power consumption and eventually damage the cards).

The language card is built into the IIe and later machines,
appearing as if it is in slot 0.  


A "slinky" RAM card does not remap the Apple II memory.  Its RAM is
accessed through a single byte I/O register, with a three byte address
register that is automatically incremented for each RAM access.  To
copy a block of data in or out of the card, you set the initial
address then read or write the data I/O location for each byte to be
read or written.  There is no bank switching.

The SmartPort or ProDOS block driver firmware on the card is normally
used by programs to access the RAM on the card.

A "slinky" RAM card cannot be used in slot 0, as most software
requires the firmware on the card, and slot 0 has no support for
on-card firmware.

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