>>716497842
It's a hardware debug tool called Address Checker. It basically checks if games use memory addresses they should not be, to make sure no software does something that may break on potential future revisions (dieshrinks, ram carts, etc).
For example the 1 MB RAM carts will show up in memory mirrored across a memory region. Meaning, you have several megabytes of data repeating the data from that 1MB extra memory on the cart. It works like that because any address lines that should point above 1MB will point to nothing, so reading data from 1MB + #1 byte will return the same as reading byte #1.
In this case, reading the first 1MB is correct, but reading the mirrored segments is bad. Because if a cart should come out with more physical memory, the 1MB segments would not get mirrored, they would have actual physical data on them, and the game would end up reading garbage.
Which is why some SNK games only work with genuine 1MB carts, but will show garbled graphics with 4MB carts or Action Replays. So it's an actual problem that needs to be actually tested, and OP pic is to do that, but I guess they never added RAM checking in it.
They also made a second version of the address checker that uses built in leds instead. OP pic used SCSI to connect to a PC instead.
