Trollbox Trade Federation,
- Oct 15, 2007
I was wondering if it was possible to merge something like V11,V21,V22 and V23 onto a single 16Mb chip and use that with a NEO-PCM board like a PROG-4096.
It might be possible. I recently came into possession of a Blue Journey's boot that was made on a BK1 board. It had just a single rom for V1. An original Blue's Journey cart is pre-pcm so that adpcm-a and adpcm-b samples are on separate mask roms. Before I blanked out the V1 rom on the boot, I dumped it cause I was curious to how they merged the files. I split the 16mbit V1 rom in half and the CRCs match exactly for V11 and V22. V11 was the lower half and V22 was the upper half.
The following is conjecture but it may be that the PCM chip multiplexes adpcm-a and adpcm-b every 8mbits. You can try merging the roms in that fashion and see if it works. I'd try it myself but I'm fresh out of bootleg carts to use as test subjects.
Blue's Journey looks interesting in that they left v21 empty on the original board. That makes it work with the PCM since the v22 wouldn't overlap with the v11 ROM. If it used v21 + v11 (like Puzzled does) then I expect you'd have the address overlap issue.
Interesting. Didn't notice that until you pointed it out. Do you know the how multiplexing scheme works on the neo-pcm?
It's very possible and fairly simple, locate sample data table into the M rom and patch the addresses to match the new setup.
That's a one hour job for someone half competent.
That's really not the problem at hand here. Modifying pointer tables would be moot if the basic understanding of the pcm multiplexing scheme is unknown.
The "creative" bootleg implementation is functionally close to the real thing--the PCM literally just multiplexes access.