cel@CIT-HEX.ARPA (12/07/85)
There's been discussion of 256K upgrades for 800XL's and 1200's, but some
of it misses the mark for those of us with "old" 800's. The real question
is how to get maximum advantage from memory upgrades. So far, I know
of five schemes for 64K+ memory expansions:
Axlon ramdisk 128K ... don't know how it works ...
Atari 1200 (other XL?) extra 16K swapped with O.S., PORTB selected
Mosiac Select 4K banks at $C000, non-PORTB select scheme
Atari 130XE 16K banks at $4000, PORTB selected
Byte's 800XL 256K "dog" ??
The problem comes when you realized that NONE of these is standard. Yeah,
sure, Atari themselves came out with the XL's and the 130XE, but the two
aren't compatable and (worse) have little to no support from the O.S.
software.
So: how to get the best use out of add-on memory? Shall we take the
130XE as the new standard, and junk all of our old stuff? I know it's
a little late in the game to be talking about standardizing 800 add-ons,
but isn't there something we can do about it?
Now the suggestion (are you listening, C. Dave Young?): how about some
kind of software "standard" which would let you use the extra memory
regardless of what Atari it's on and how it got put there. Hide the
differences between the above systems in some sort of low-level
"extra memory" handler. Ramdisks address part of the problem, but
there are many applications for which you want memory, not emulated
disk files.
....anybody have some ideas about this?
--Chuck Lane
cel@cit-hex.arpaDYOUNG@USC-ISID.ARPA (C. David Young) (12/09/85)
Chuck, Regarding your desire for someway to standardize the way extra memory is addressed in the 8 bit ATARIs, I have come to the conclusion that we have to accept ATARI's way of doing things, e.g. via the bank select address at $D301. And I see why ATARI did it this way instead of using the well established adress of $CFFF used by AXLON: they already had $D301 decoded so that no extra logic was involved. Other than this difference, the extra memory of AXLON and ATARI look the same (i.e. the memory banks are mapped in the same place from $4000-$7FFF). I have even considered adding to the AXLON ramdisk handlers built into the OMNIMON and OMNIVIEW for the 800 the ability to convert refences to $D301 into references to $CFFF so that programs written to run on the 130XE and 800XL's with compatible upgrades would also run on the old 800 with an AXLON ramdisk (or its compatible). I may eventually do this, but for now it is too far down on the priority list to think about. As far as an extra memory 'handler' which would allow programs to address the extra memory banks as if they were merely an extension of the 6502 address space, the only practical solution that I can come up with is to buy an ST. David Young CDY Consulting -------