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Atari 1200XL upgrade problem

1200xl 512K 256K 32-in-1 OS

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#1 oracle_jedi OFFLINE  

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Posted Sun Jul 8, 2012 2:29 PM

Some time back I added the 32-in-1 Atarimax upgrade to my 1200XL.

All was good.

Then I added the Atarimax 256KB upgrade, and that was cool too.

Some time after that I added the extra 256K memory and things went pear shaped.

The 32-in-1 OS started reporting "Communications Error" instead of the currently selected OS, the self-test crashed at the conclusion of testing the 48 memory blocks, and SRAM021 reporting errors across all the extra 256K. But everything still worked and 256K games played okay.

Steve was great in helping me diagnose some of the problem, and the R59 connector was moved to pin 17 of PIA. That fixed the "Communications Error" problem, but the self test still crashed and I never did figure out the problem with the top 256K.

Yesterday I triled to pull the extra 256K out. I removed all the stacked memory chips and replaced them with eight new 256K devices. All the extra wiring for the 512K upgrade was pulled out and the R59 connector restored. I have tried to repair the broken pin 17 of PIA with a wire soldered to the bottom of the board connecting to the snipped pin 17 of the chip.

Now however nothing works.

The 1200XL will boot to the OS selector and I can select an OS. The OS selector shows the currently selected OS.

Self test will lock up on ROM test, or report most of RAM bad. It frequently crashes. If it makes it to the audio test the display is usually corrupted in some manner, and it has yet to make it voice 3. The shift keys have stopped working. If I select the 1200XL OS I get the rainbow logo but parts of the display are missing.

I have put another set of eight RAM chips in and got the exact same result. I don't think this is RAM.

So what is the most likely next candidate? Is the PIA fried? The MMU? What failure most likely explains failing ROM/RAM self test, failing voice 3 (lock up), some of the keyboard not responding? This is not a typical 1200XL keyboard problem. I can test this keyboard on another 1200XL and it works great.

Any help appreciated.

Thanks

Graham

#2 Rybags ONLINE  

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Posted Sun Jul 8, 2012 2:35 PM

The 32in1 uses bit 7 of the PIA to communicate with the PIC that controls OS selection. That bit also controls if Self Test Rom is in or out.

A better approach might have been taking the 32in1 out and getting the Ram working with a normal OS, although doesn't the 1200XL require other mods to get 32in1 going in the first place?

It might be that your PIA has gone bad. But it's got nothing to do with the keyboard, Pokey handles all the keyboard except console keys & Reset.

#3 Stephen OFFLINE  

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Posted Sun Jul 8, 2012 3:46 PM

Phi02 timing issue is a possibility.

#4 oracle_jedi OFFLINE  

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Posted Sun Jul 8, 2012 10:58 PM

A better approach might have been taking the 32in1 out and getting the Ram working with a normal OS, although doesn't the 1200XL require other mods to get 32in1 going in the first place?


The 32-in-1 does require quite a number of modifications to install. Taking it out wont be easy.

The Atarimax 256K upgrade requires 8 trace cuts which would even harder to reverse.

Is the PIA from an 800XL compatible with the one from a 1200XL? I think I am going to try replacing PIA since I have a spare in my parts bin.

#5 bob1200xl OFFLINE  

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Posted Sun Jul 8, 2012 11:27 PM

The PIAs can be swapped. Try it.

You seem to be saying that the diagnostics do not work properly but games will? Can you get the ED/ASM cart to work? You may get a better idea of memory errors using the debugger.

Bob

or, do you have a debugger in the 32in1?


A better approach might have been taking the 32in1 out and getting the Ram working with a normal OS, although doesn't the 1200XL require other mods to get 32in1 going in the first place?


The 32-in-1 does require quite a number of modifications to install. Taking it out wont be easy.

The Atarimax 256K upgrade requires 8 trace cuts which would even harder to reverse.

Is the PIA from an 800XL compatible with the one from a 1200XL? I think I am going to try replacing PIA since I have a spare in my parts bin.



#6 oracle_jedi OFFLINE  

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Posted Tue Jul 31, 2012 3:00 PM

After reading the 800XL memory thread started by Marius1976, I tried swapping the MMU and everything started working.

Additional help from Steve had me replace the CMOS RAM chips with NMOS RAM chips and the 1200XL is now running reliably again.

Thanks to everyone on this thread, Steve and Marius.




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