Hey,
Just wanted post this in case someone else comes across this problem. My Marble Madness was working just fine for a long time, then out of the blue one day it booted to "Bank Switch Error". Searching around, everyone seemed to point to a bad Slapstic... which of course sucks, because there's no replacements available. Luckily, Marble Madness is compatible with the Roadblasters chip, which is cheaper/easier to find... but still not cheap. So, I started looking into how they work, and possibly making a replacement.
Then, I figured that I'd try testing the Slapstic with the logic probe, and surprisingly, it seemed to be working (looked similar to what was happening in the log in mame w/ LOG_SLAPSTIC defined in slapstic.c ). But, looking at the schematics, I figured that an error caused by a bad Slapstic would be the same as an error caused by the ROMs that the Slapstic drives. Probing them found one pin that never changed on chip 13A. I dumped the ROM, and yep... one bit was stuck high. This was a 23128, which has a compatible pinout with a 27C128. I burned the good file to a 27C128, replaced it, and the game came right back up.
So... I just wanted to document that before putting all bets on a bad Slapstic, dump the Slapstic ROMs (13A and 14A on a MM board). I wish I had done that from the start (would have taken no more than 5 mins), before spending all that time trying to figure out how to bypass or recreate the Slapstic, though I guess at least now I understand how a Slapstic works
.
DogP
Just wanted post this in case someone else comes across this problem. My Marble Madness was working just fine for a long time, then out of the blue one day it booted to "Bank Switch Error". Searching around, everyone seemed to point to a bad Slapstic... which of course sucks, because there's no replacements available. Luckily, Marble Madness is compatible with the Roadblasters chip, which is cheaper/easier to find... but still not cheap. So, I started looking into how they work, and possibly making a replacement.
Then, I figured that I'd try testing the Slapstic with the logic probe, and surprisingly, it seemed to be working (looked similar to what was happening in the log in mame w/ LOG_SLAPSTIC defined in slapstic.c ). But, looking at the schematics, I figured that an error caused by a bad Slapstic would be the same as an error caused by the ROMs that the Slapstic drives. Probing them found one pin that never changed on chip 13A. I dumped the ROM, and yep... one bit was stuck high. This was a 23128, which has a compatible pinout with a 27C128. I burned the good file to a 27C128, replaced it, and the game came right back up.
So... I just wanted to document that before putting all bets on a bad Slapstic, dump the Slapstic ROMs (13A and 14A on a MM board). I wish I had done that from the start (would have taken no more than 5 mins), before spending all that time trying to figure out how to bypass or recreate the Slapstic, though I guess at least now I understand how a Slapstic works
DogP
