Does Joust mess with high scores?

westal_sage

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I've noticed my Joust seems to shift the high score table around. At first I saw that every so often it would clear out the bottom 4 scores or so - reset them to 4000 and like some preset initials. But at least all of the other scores remained intact. I was thinking it might do this to encourage play.

But today it looks like it shifted the table so that about 8 of the bottom scores reset, but a bunch of the highest scores are now gone. The top score is now what was maybe #8 or so. But other than the shifting, all of the scores were there before (it's not like it totally reset the table).

I'm guessing this isn't normal. Could it be because there's a switching PS in there?
 
Could it be because there's a switching PS in there?

Yes, this is a known problem when running a switcher in a Williams game. It has to do with the sequence in which power supply voltages drop when the game is powered off. Normally with the original linear supply, the 12V drops sooner than the 5V, which is detected by a circuit that write-protects the CMOS SRAM where the high scores are stored. With a switcher, this doesn't happen, so the CPU writes out garbage to the CMOS SRAM before it is write-protected.

You can either put in an original linear supply (there are folks on here who rebuild them) or replace the CMOS chip with an NVRAM adapter. There is a nice gentleman on here who makes NVRAM adapters for this purpose. ;) http://forums.arcade-museum.com/showthread.php?p=1965546#post1965546
 
Ah yes, a nice gentleman indeed with a thoughtful reply. Thanks! I sent you an email requesting to purchase one of these cool adapters. Thanks again! -Wes
 
Yes, this is a known problem when running a switcher in a Williams game. It has to do with the sequence in which power supply voltages drop when the game is powered off. Normally with the original linear supply, the 12V drops sooner than the 5V, which is detected by a circuit that write-protects the CMOS SRAM where the high scores are stored. With a switcher, this doesn't happen, so the CPU writes out garbage to the CMOS SRAM before it is write-protected.

You can either put in an original linear supply (there are folks on here who rebuild them) or replace the CMOS chip with an NVRAM adapter. There is a nice gentleman on here who makes NVRAM adapters for this purpose. ;) http://forums.arcade-museum.com/showthread.php?p=1965546#post1965546

how did you get that to point to that exact post????
 
how did you get that to point to that exact post????

Find the specific post you want and look in the top-right corner for the post #:

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Click on it and it opens a page showing that single post. At the top-right of the "view single post" page is a link back to the thread:

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Click that link and it takes you to that particular post within the full thread. Just copy and paste the URL from the address bar of your browser to use the link elsewhere.
 
The switcher / NVRAM sequencing corruption would have been my guess too, but doesn't that cause a full reset to defaults (losing the entire score table)?

I assumed the code keeps a checksum in there, and resets to defaults if any portion gets corrupted and causes an incorrect checksum on the next boot. The problem here sounded a little more specific, since the entries were mostly preserved but shifting locations.

On a side note, I love using MAME to get insight into things like this. E.g. You could set a breakpoint on read/write accesses to the NVRAM address range, then watch and see exactly how it manages the NVRAM data.

LeChuck
 
The switcher / NVRAM sequencing corruption would have been my guess too, but doesn't that cause a full reset to defaults (losing the entire score table)?

I assumed the code keeps a checksum in there, and resets to defaults if any portion gets corrupted and causes an incorrect checksum on the next boot. The problem here sounded a little more specific, since the entries were mostly preserved but shifting locations.

IIRC, my Joust would often lose a few high scores here and there, rather than fully resetting to defaults before I installed the NVRAM. Good point about the checksum though, I've never looked into how that works. I'm sending the OP an adapter to try, so we'll see.
 
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