tr-626

[Gordonjcp]

Experiment...  I can't remember where I got the spec for the 505 ROM, but most ROMs follow a fairly standard "pattern" of pin connections.  Actually decoding the ROM was partly guesswork, partly experimentation and partly measuring the frequencies of the pulses on the TR626 ROM address lines.

Lots of beer helps, too.  I recommend a fairly light pale ale to start with, perhaps something like Badger Dorset Ale, or maybe Harviestoun Bitter & Twisted, or even Houston Killellan (not really an IPA but still worth a go).  As you get deeper into the mysteries of the ROM you might try something like Badger Tanglefoot or maybe Kelburn Red Smiddy (quite light, you'll need a lot of this) or of course Orkney Dark Island.  Obviously if these beers are unavailable then you can substitute some locally-available real ale.

Really it comes down to this:  have a pencil and paper, and know how to use it; have some real ale, and know how to use it; and have an oscilloscope or signal tracer, and know how to use it.

Hope this helps.  Good luck!