Super interesting that when you were looking at the diff between the known good ROM image and the one you pulled off the chip, ALL of the incorrect bit pairs had only shifted one place to the left. What in god's name would cause seemingly random bits to _all_ shift one place to the left? (i.e. 5C becomes 5B, 43 becomes 42, etc...) I've watched a few videos on "earth level radiation" (the low-levels of radiation coming from our sun and the environment around us) causing "bit flip" in memory (where a 1 becomes a 0 or vice versa) in memory, causing otherwise unexplainable blue screens/kernel panics. Given that these are ROMs we're talking about, I can't imagine any other hardware on that board actually managed to _write_ those incorrect bits to the ROM chip, so I wonder if the cause of this issue was something like a bad ground, transient spikes, or even low-level radiation! I'm sure there's some more mundane explanation (which I'd love to hear your thoughts about!), but it's fun to think about stuff like this =P
Super weird isn't it? Wait until you notice that the bad byte is in the same column every time! I'm guessing there's something structural in the EPROM that has failed.
@@74XX_arcade have you ever seen something like this before? I've never worked with arcade hardware (nor have I ever had to dump the contents of a physical ROM chip using a reader like yours), but I have dumped firmware from (and flashed firmware _to_ ) several devices (each of which have used non-removable EEPROM), and I've never seen any issues this weirdly _consistent._ I've dealt w/ motherboard/GPU firmware corruption, but in those cases, the corruption is pretty severe. I've seen scenarios where the corruption is so bad, some characters within the ROM don't even match my system's supported languages or installed character sets. Issues like this one - where the problem bits follow such a consistent pattern - really make me wonder what a deep dive would uncover regarding the root cause of the problem at a _physical level_ (because there's got to be some underlying physical issue with some aspect of the chip, right?) If so, it'd be super neat if it were possible to _see_ any physical deformation using a powerful microscope (like a Mantis or equivalent). Not suggesting _you_ should take all the time to do that, because de-lidding these chips requires those laser systems and all that (and even then, the chip die is so freaking small that I'd imagine you'd need some super expensive, super high magnification equipment like an SEM or something like that to actually _see_ the physical defect). The 9-year-old in me loves thinking about what that sort of problem must look like on a physical level though, haha. Anyway, one more question and I'll stop my rambling: What do you think could've caused the potential defect within the chip itself? I'm thinking maybe a transient spike or perhaps an overheat, though to my knowledge, these game companies tried to make these boards pretty resilient to stuff like that to keep them in operation.
Kinda sucks. If bits on EPROMs flip from 0 to 1, then it's easy - just burn the image over the original, that works most of the time. Sometimes, the ROM's bad. But if bits flip from 1 to 0, the ROM's always bad. Sometimes EPROMs that become flaky also get a lot warmer than they should. My guess is that something in the internal addressing logic fails the speed test due to age (there's electron migration, I guess that takes active material away from being a transistor so the transistor gets weaker and weaker as it ages). Flips from 0 to 1 are usually due to stray UV radiation or sometimes can happen with age, but as I said, in that case, the EPROM will happily accept its original program after burning, and if not, in the trash it goes.
Hi, thank you for making this repair video, I learned a lot. I have this game PCB and it showed sub CPU ROM error when I boot up the game. Could please help me by telling me which file should I write into the EPROM? Thank you.
![Galaga [Fast-Fire] - MAME - 20,518,900 (WR!)](http://i.ytimg.com/vi/WUKTMLi1GhM/mqdefault.jpg)
Happy new year! Would love to see more repair videos if possible. 🙂
Your videos are awesome ! how much do you charge ?
Dude, just discovered your channel. You need to do more vids. They are very well done!
Super interesting that when you were looking at the diff between the known good ROM image and the one you pulled off the chip, ALL of the incorrect bit pairs had only shifted one place to the left.
What in god's name would cause seemingly random bits to _all_ shift one place to the left? (i.e. 5C becomes 5B, 43 becomes 42, etc...)
I've watched a few videos on "earth level radiation" (the low-levels of radiation coming from our sun and the environment around us) causing "bit flip" in memory (where a 1 becomes a 0 or vice versa) in memory, causing otherwise unexplainable blue screens/kernel panics.
Given that these are ROMs we're talking about, I can't imagine any other hardware on that board actually managed to _write_ those incorrect bits to the ROM chip, so I wonder if the cause of this issue was something like a bad ground, transient spikes, or even low-level radiation!
I'm sure there's some more mundane explanation (which I'd love to hear your thoughts about!), but it's fun to think about stuff like this =P
Super weird isn't it? Wait until you notice that the bad byte is in the same column every time! I'm guessing there's something structural in the EPROM that has failed.
@@74XX_arcade have you ever seen something like this before?
I've never worked with arcade hardware (nor have I ever had to dump the contents of a physical ROM chip using a reader like yours), but I have dumped firmware from (and flashed firmware _to_ ) several devices (each of which have used non-removable EEPROM), and I've never seen any issues this weirdly _consistent._
I've dealt w/ motherboard/GPU firmware corruption, but in those cases, the corruption is pretty severe. I've seen scenarios where the corruption is so bad, some characters within the ROM don't even match my system's supported languages or installed character sets.
Issues like this one - where the problem bits follow such a consistent pattern - really make me wonder what a deep dive would uncover regarding the root cause of the problem at a _physical level_ (because there's got to be some underlying physical issue with some aspect of the chip, right?)
If so, it'd be super neat if it were possible to _see_ any physical deformation using a powerful microscope (like a Mantis or equivalent).
Not suggesting _you_ should take all the time to do that, because de-lidding these chips requires those laser systems and all that (and even then, the chip die is so freaking small that I'd imagine you'd need some super expensive, super high magnification equipment like an SEM or something like that to actually _see_ the physical defect).
The 9-year-old in me loves thinking about what that sort of problem must look like on a physical level though, haha.
Anyway, one more question and I'll stop my rambling: What do you think could've caused the potential defect within the chip itself? I'm thinking maybe a transient spike or perhaps an overheat, though to my knowledge, these game companies tried to make these boards pretty resilient to stuff like that to keep them in operation.
Kinda sucks. If bits on EPROMs flip from 0 to 1, then it's easy - just burn the image over the original, that works most of the time. Sometimes, the ROM's bad. But if bits flip from 1 to 0, the ROM's always bad.
Sometimes EPROMs that become flaky also get a lot warmer than they should.
My guess is that something in the internal addressing logic fails the speed test due to age (there's electron migration, I guess that takes active material away from being a transistor so the transistor gets weaker and weaker as it ages). Flips from 0 to 1 are usually due to stray UV radiation or sometimes can happen with age, but as I said, in that case, the EPROM will happily accept its original program after burning, and if not, in the trash it goes.
Hi, thank you for making this repair video, I learned a lot. I have this game PCB and it showed sub CPU ROM error when I boot up the game. Could please help me by telling me which file should I write into the EPROM? Thank you.
I have an arkanoid 2: revenge of doh that I can't get working... I don't have an EPROM tester or writer... do you sell replacement EPROM sets?
Hi Michael, I don't but the go-to place seems to be hobbyroms.com. I haven't used them but I've been told they will sell pre-programmed EPROMs.
Homer Simpson
What does the SUB CPU do? the purpose of the SUB CPU is doing what
Running the sound effects and music