Subject: Re: Accessing other aux banks in RAM cards
Newsgroups: comp.sys.apple2.programmer
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From: david@uow.edu.au (David Wilson)
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Date: 1 Jul 2000 16:40:01 +1000
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bobryan9@my-deja.com writes:
>I can access the aux memory in a 128k apple card now.  This gives me
>128k to work with.  Thanks to Dave for the information on programming
>the softswitches.

>Now I'd like to access more than one bank, like on a RamWorks III.  I
>have a QRAM IIE (the one that WAS sold by Quality Computers).  It has
>1024k.

If you read the Tech Ref Manual for the //e you will find that the only
I/O space decode that is present in the Aux slot is C07X. What the various
manufacturers have done is decode this further with the low order address bits
0..3 to give a one byte write-only bank register, probably at $c073 or another
odd address in the range $c070..c07f ($c07x is used to trigger the 558 used
by the joystick so picking an odd address avoids most programs messing with
the bank register (as they typically use $c070). If $c073 does not work try
$c071 or $c075. This one byte register could select up to 256x 64KB banks so
on a 1MB card it will probably ignore the top 4 bits.

>Did the apple 1 megabyte 'slinky' card act as bank switch memory or
>just a RAMDISK?  I've never used one.  What is it's method of switching?

No, the slinky card uses 4 bytes in the slot I/O space used by the slot the
card is in. If I remember correctly, $c0m0 is the LSB, $c0m1 is the middle
byte and $c0m2 is the top byte of the 3 byte address (less top 4 bits).
$c0m3 is a one byte read/write port to the address selected above. The neat
trick with the slinky card is that each time you read or write $c0m3, the
address contained in the other three bytes auto increments making it easy
to copy a block of memory into (or out of) the card.
--
David Wilson  School of IT & CS, Uni of Wollongong, Australia