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Ultimate 1MB goofy screen?

Smokeless Joe

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I thought I saw a thread on this, but I can't find it.

Every so often, when reconfiguring my U1MB, I get a screen that looks like the attached image.

Any ideas what's going on?


Yes, maybe... See here...


But I guess, you don't want to hear it...



Edited by Stefan Both
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I resoldered all my connections, this time using the connections suggested by FJC at http://atariage.com/forums/topic/224151-ultimate-1mb-in-1200xl/?p=3163936 but that didn't change much.


So I tried updating the BIOS with the fancy new ones FJC made. On startup it loads normally but if I hold down the HELP key and press the RESET key I get either a blank screen or the picture below.

This does not happen in my 800XL with the very same U1MB installed; I can hit HELP-RESET all day and it never says boo.
Stefan's thread seemed to suggest that he had a questionable power supply. I have two power supplies and switching them out doesn't seem to make a difference.
Any other ideas?


Edited by Smokeless Joe
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The last time I saw a screen like the one in post 1, I'd connected one of the four auxiliary connections to the wrong via on the motherboard. Antic is unable to properly address the display RAM. It sounds as if you still have some serious address line/stability issues.

Interesting that you bring up the display. I did a SuperVideo 2.1 modification on this motherboard, could that have something to do with it?


It puzzling that it's intermittent, though. It can work, just not reliably.

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Modifications to the video signal's output path shouldn't have any effect here. Minute solder bridges, marginal contacts, or Phi2 problems are likely to blame. Did you replace the OS ROM and MMU sockets, or fit sockets in place of soldered ICs? Did you use precision sockets or single/double wipe? Did you use a dupont connector for the aux pins or solder wires direct? Just listing all the usual points of interest here.

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I have never had a screen quite as... original as in post 1, but I did run in to an issue where on opening the Help+Reset menu a solid white line appeared on the right hand side of the screen while all the text and graphics were still present and correct. Interestingly I found it went away after a couple of seconds.

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  • 2 weeks later...

To answer FJC's questions:

a. I used the sockets that were already on the motherboard. I did not replace the sockets nor were the ICs soldered in.

b. The existing sockets look like double wipe.

c. Dupont connector. I take pride in the aesthetics of my work!


I installed the same U1MB into another 1200xl motherboard and it seems to work fine. Just like in my 800xl, I can hit Help-Reset all day long and the U1MB doesn't blink. At least I have one functional 1200xl with the U1MB, but it's kinda sad the other one is so uncooperative.


So what's the difference between the two motherboards? The board that doesn't work reliably has the SuperVideo 2.1 mod and the RF module removed (all by me), I got it from Best Electronics and it has some Atari brand scotch tape over a few of the chips. The board that seems to work reliably has no mods except the W jumpers removed and W11 jumped to work with the U1MB, I got it off eBay and it's a lot more shiny that the first one.


My guess is that I broke something with the extensive modifications on the first board. Would a SALT cart maybe help diagnose what the problem is? Any other diagnostics anyone could recommend?

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I had similar problems with a U1MB install in my 1200XL's (both of them). The same board is rock solid in both my 800XL's. I've chalked it up to quirks in the 1200XL and left it installed in an 800XL, where it's happy as a clam.


Which reminds me ... at some point I need to reinstall the jumpers I removed for the 1200XL installation and put the original OS ROMS and MMU back in ... Maybe next weekend.

Edited by DrVenkman
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Diagnosing bus instability with scopes, etc, is beyond my skill level, but I always replace the OS ROM and MMU sockets with precision versions during an Ultimate install. Original sockets may be OK, but fitting new ones just removes another possible variable if done correctly. After that, I'd start swapping ICs (including the CPU) before my checklist was exhausted. :)

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