So the other week I ordered Pier Solar, and was cleaning out my X'Eye to make sure that the cartridge slot still behaved as it was supposed to. It's historically been kind of finnicky! Anyway, the method I'd been recommended for cleaning a test cartridge with alcohol (in my case, I used Flashback), then once it was dry inserting and removing it from the cart slot and swabbing off whatever dirt and grime came out with it.

So, the first couple of times I got nothing. No big surprise. Very last time, I got it to boot. Which is great! But in the meantime, just before getting it to boot, I got this really weird thing:



I don't really know what to make of this! I don't know whether this is part of Flashback or part of the X'Eye. It certainly seems to be some sort of "oh damn the game crashed" debug screen, but the game basically booted straight to this.

What am I looking at? Has anyone seen this before?

This was discussed on the SpritesMind forum already, but I'll say it here too for those who are curious:

This is a 68000 exception (not Genesis-specific) that occurs when the CPU runs an opcode whose uppermost nibble is $F (%1111; these first nibbles are called "lines," hence LINE %1111 or F-line). The entire range of these opcodes are reserved by Motorola for future use (and indeed, some are used by later members of the 68000 family — for example, for coprocessor instructions (such as FPU instructions) and the 68040's move16 instruction). This usually happens for one of two reasons — either the program somehow jumped into data or there's something corrupting the bits the 68000 reads (bitrot? dirty connectors on the cart or hardware?).

Line 1010/A-Line is similar — the $Axxx range is reserved for system calls, and indeed some systems use them. I know the Japanese Mega Drive game Star Cruiser does — but since that's a port of a X68000 game, I'm thinking that's the case with the X68000 too?