[sdiy] 'Decoding' Drum machine sample ROMs?

[Colin f]

> What
> I think has been done is (for ease of PCB routing) address 
> lines and/or data
> lines have been re-ordered; with the result that the kick 
> EPROM sounds like
> nasty digital noise :(

This is the case for the 909 cymbal ROMs too.
 
> So, my question: is there any reasonable strategy to finding 
> out the correct
> ordering of the data/address lines (I can write a program 
> which will re-order
> the data if I know the scrambled order!) - or better still, 
> does anyone know
> what order the address lines are connected!?

In the case of the 909, I worked out the address order from the way the
counters were driving the address lines of the ROM, and the wiring from the
data outputs to the resistors of the DAC. But I later decided it would be
safer just to 'sample' the data in the correct order by wiring up a computer
to the data and clock lines, and triggering the sample - this meant I didn't
have to risk removing the soldered-in ROMs from someone else's 909.
I already wrote a bitswapper program, if you find out the required mapping I
can mail you the exe.

Cheers,
Colin f