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What is this 800XL mod/upgrade and issues


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I bought this 800XL years ago on Ebay. It has built-in SpartaDos 4.21 upon powerup


However, the cartridge doesnt work (black screen no matter what cart) and Basic doesnt work (says Not Present! When I do Car or Basic


See attached pic. Did the sparta rom just replace the Basic Rom? Whats with all the wires and epoxy? Is all of this just to get SpartaDos on MB?


My questions:


1 did this upgrade kill the cartridge or just coincidence


2 is there a powerup keypress to load cart or basic?


3 can I revert out of this upgrade if I want to do the ultimate 1mb or other upgrade




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Good lord, what a mess!

​First off, the green wire to the left is probably one of the many "factory hacks" or "bodges" you see pretty often on the 800XL - two of mine (Rev C boards) have something similar along that side of the board, for no particular reason that anyone has ever been able to definitively determine.


As for the board, it looks like some sort of memory upgrade too, whatever else it may do. There are wires running to the PIA and MMU. Personally I'd cut all that stuff out if possible ... but ugh, all that epoxy. I hope you can get it out without a Dremel ...

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i can't see what you have to lose by "undoing" the upgrade.


i'd remove the breadboard, and replace with standard IC.

is everything ok?

if so, then you know for sure it's the board or one of the connections.


if you want to lose it you can - and if you don't fancy desoldering - then some small snippers can cut the cables right at each connection.

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The wires to the MMU are probably for cartridge handling (RD5 and S5 on MMU).


But what has happened to PIA. Are there pins cutoff? Are you sure the PCB of the 800XL on the bottomside is untouched? I'm afraid with this kind of crap, that the bottom side is going to be a unpleasant surprise.

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Weird, the pickoffs from PIA are R/W and Phi2. I'd have thought maybe there'd be an closer place to get them? R/W is bottom side of the PBI but Phi2 is at the top and very close.


Are those PIA pins actually cut? They are the PB2-PB6 pins, normally unused on 800XL.

Looks like there's a line to pin 10 of U2, 74LS138 I/O select which corresponds to /CCTL which would allow banked cartridge emulation.


My guess is that this would have been a functioning upgrade but just losing a single connection somewhere could be sufficient to render it partially or fully inoperative.



In the modern day it's cheap and easy to get the functionality on offer here, either AtariMax flashcart with SDX onboard, SIDE cart or Ultimate 1 Meg to name just a few.

So probably not worth worrying too much about getting it working properly although getting rid of it could be an even harder chore.

Edited by Rybags
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Have you tried typing the command MEM to see what the lomem and himem is..?


Yes MEM shows Main: $17AA, $17AA, and Ext: $FEC5, $FEC5. How much mem does this indicate?


The bottom of the board is clean other than some diodes that look patched in, but could have been stock


I wonder if the Epoxy itself is shorting something? maybe its partially conductive. I don't see any breaks in any of the wiring.

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Just a normal 64k memory.


Your could search for a loadable basic like turbo basic for SpartaDos called TB32Q.COM or an Atari basic that is rom2xex conversion.


Atari++ emulator has a new basic out and I use it often. Altirria emulator has a basic version ATBASICX.COM 1.53 that is in the additions.atr delivered in the emulator test 32 zip file.


Also the cartridge may be fix for Banked Cartridges like Basic XL/XE, Action, and others.

Edited by rdea6
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This upgrade hooks to the MMU, if RD4/RD5 lines has been routed then it will effect the cartridge behavior when you plug one int.


everything can be reversed but the Gray residue looks like epoxy glue, trying to remove it may lift some threads on the pcb and you dont want that,

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