I bought an Atari 800 a couple of months ago.
But with only 48Kb, I won't be able to use SpartaDos X.
I can wait for the next production run of Incognito but in the meantime, I need another solution which is Axlon compatible.
I am not a hardware guru so I searched for a 256Kb upgrade on the net.
I found several old articles (thanks to AtariAge messages) :
- The Atari 800 Plus 256K by David G. Byrd
- Windhover project by Jay Torres (reprinted in SaintPaul Atari Computer Enthusiast). The article explains a 64Kb upgrade, a 128Kb upgrade and then 256Kb upgrade)
- The WindHover 288K SuperRam Modification also by Jay Torres
And some articles by Claus Buchholz here in this forum.
And I appreciated also the article explaining how the design of the 800 supported any memory configuration (with the RAMSLOTS.BAS program)
The first 3 articles have the same overall approach and use almost the same components.
I wanted to understand the differences in a logical diagram to be able to choose one.
So I took the excellent diagram from Jerzy Sobola and, for each upgrade, I drew in red the modifications.
I wanted to share this work with every one, This is what you will find in the archive.
The second goal of this article is to simplify the upgrade and check with hardware gurus if my changes are right.
All the upgrades have 2 major disadvantages :
- you need to add wires in the bakplane (the mother board)
- you need to cut traces on the 2 other 16Kb boards
I took the first one (by David Byrd) and tried to make changes to keep the addressing cycle explained in RAMSLOTS article so there is no need to cut traces in other boards.
And I also removed the wires to the backplane so there is only the ROM board and the 16Kb board in Slot 2 to change.
Of course, without mother board wires, the 2 boards (ROM and 16Kb) need to be connected board to board.
There is only one wire which is missing: the RES M pin from the CPU board was wired to the MR pin of the 74LS175.
I don't know if I can live without this wire (I guess yes but I need advices).
Here is the final diagram where you have both the 16Kb and the ROM upgrade (Axlon compatible, no more D7xx)
Thank you for telling me if this version could work or if I made a mistake.
Edited by ebiguy, Sun Sep 13, 2015 4:30 AM.