[khedoros1]

> The original console has to decode the data and get it to the CPU somehow, and if you can run your own code on the CPU, you can always dump, even if it is just by displaying a series of 2-d bar codes on a TV screen and taking photos of them.

That would be a novel hack, and I've considered something similar with an old IBM computer with an almost-dead floppy (probably a stretched drive belt?) The floppy will read something like the first 50-100KB from a disk, and fails on the rest. That'd easily be enough for a little program that reads the hard drive sector by sector, displaying them on screen as a colored grid, or something. Then it'd be an exercise in video processing to extract the data.

[logfromblammo]

Not novel. I heard about it from a possibly apocryphal espionage story wherein a program was loaded to an airgapped machine, then it flashed a rapid sequence of 2-d bar codes on the screen, and the attacker exfiltrated the data as a video file.

For your problem, I'd try pumping the data out of the serial or parallel ports first. An RS232 to USB cable might work.