I am not sure what the point of this would be, To understand a PROM dump you often need to know a lot more than that, in fact you often need schematics, (and maybe PAL equations, etc) for the device it goes in. And if you have that, most of these questions are answered. For PROms with word lengths <=8 biMs (which covers just about all 'classic' ones, it's normal to put one word pe byte, in the low bits of the bute and pack with 0s's. So a 256*4 dump would be 256 bytes long, the high nybble of each byte of the dump woul;d be zero. If it is, that doesn't tell you everything about it Not all character generators are simple bit-maps. In particular, many character cells on older terminals.dispalys were 7 bits wide, but normal 8-bit EPROMs were used for the chaacter generator. Thie extra bit of the EPROM (often the MSB) was used i na variety of ways, 2 common ones being to extend the last bit sent to the screen into the inter-character gap (so that line drawing chartacters join up), or to signal that this row of the pattern should be shifter by half a dot width to get smoother diagonals (som HPs did that certainly. Again, you'd need to know a lot about the CPU architecture to make sense of it if it was. Porbably a schematic would be a good start... And the schematic will show the size/organisation of the PROM. That would eb a good start, but again you need to know things like the I.O structure to fully understnad the code in tha lot of cases. Does that matter? Many manfacturers used a variet of makes of PROMs at differnt times, based on cost/availability/... I don;'t think it matters that the PROM dump came from an MMI PROM and that the machine you're fixing has an equicalent (for reading at least) National Semiconducator PROM in it. Why on earth odes that matter? Actually, in a lot of cases for older machine, the metadata would be several times the size of the PROM dump. 32*8 (thats' 32 bytes, not Kbytes) PROMs were common, used for address decoders, microcode funciton decordes, state machine tables, etc. I susepct specifying the machine it came out of, the lcoation in the circuit, the basic fuction, and the organisation, would take a lot more than 32 bytes. -tony