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Ken, if you have some spare bandwidth I have some high-res decap photos from the chip in the Casio SK-1! I worked on trying to reverse engineer the instruction

Ken, if you have some spare bandwidth I have some high-res decap photos from the chip in the Casio SK-1! I worked on trying to reverse engineer the instruction set from that chip, but most of the code is in a mask ROM that probably needs some debug wires to extract.

nobleach 3y ago
The demo song from that thing will forever live rent-free in my head. Sometimes I sing it to myself, and then pretend I've switched the lead instrument to a sample. (hi, hi hi hi, hi hi hi, hi hi hi hi hi....)
ajxs 3y ago
There's a zip file here with the Casio SK-1 ROM: https://dbwbp.com/index.php/9-misc/37-synth-eprom-dumps https://dbwbp.com/index.php/9-misc/37-synth-eprom-dumps Maybe this could help. Is there some mask ROM on the CPU that isn't included here?
- mmastrac 3y ago
  Correct. Those have been available for ages, but there's a mask ROM on the CPU that is undumpable, at least at this time. I have a huge collection of datasheets and I was unable to even figure out what the instruction set was.
  - userbinator 3y ago
    It's likely to be something Japanese, and I know there's been plenty of obscure architectures from them over the years. OKI is known to have made the CPU for Casio, so have you ruled out OKI nX-8?
    - mmastrac 3y ago
      Scanning through my old datasheets I have one from the MSM65512 which probably means I considered that but it's been a while. I should have kept a devlog. I found an old email to someone that suggests I thought it was an nX/4. This is a lower-res version of the decapped chip. https://upload.wikimedia.org/wikipedia/commons/4/44/Oki_m6283_metal.jpg https://upload.wikimedia.org/wikipedia/commons/4/44/Oki_m628...
kens 3y ago
Thanks. Much as I'd like to reverse-engineer the Casio SK-1 chip, I'm trying to stay focused on my current projects.
johndmcmaster 3y ago
Consider asking in the sipr0n discord decap-commission channel: https://discord.gg/qyne7GZk https://discord.gg/qyne7GZk

nobleach 3y ago

The demo song from that thing will forever live rent-free in my head. Sometimes I sing it to myself, and then pretend I've switched the lead instrument to a sample. (hi, hi hi hi, hi hi hi, hi hi hi hi hi....)

ajxs 3y ago

There's a zip file here with the Casio SK-1 ROM: https://dbwbp.com/index.php/9-misc/37-synth-eprom-dumps https://dbwbp.com/index.php/9-misc/37-synth-eprom-dumps Maybe this could help. Is there some mask ROM on the CPU that isn't included here?

mmastrac 3y ago
Correct. Those have been available for ages, but there's a mask ROM on the CPU that is undumpable, at least at this time. I have a huge collection of datasheets and I was unable to even figure out what the instruction set was.
- userbinator 3y ago
  It's likely to be something Japanese, and I know there's been plenty of obscure architectures from them over the years. OKI is known to have made the CPU for Casio, so have you ruled out OKI nX-8?
  - mmastrac 3y ago
    Scanning through my old datasheets I have one from the MSM65512 which probably means I considered that but it's been a while. I should have kept a devlog. I found an old email to someone that suggests I thought it was an nX/4. This is a lower-res version of the decapped chip. https://upload.wikimedia.org/wikipedia/commons/4/44/Oki_m6283_metal.jpg https://upload.wikimedia.org/wikipedia/commons/4/44/Oki_m628...

kens 3y ago

Thanks. Much as I'd like to reverse-engineer the Casio SK-1 chip, I'm trying to stay focused on my current projects.

johndmcmaster 3y ago

Consider asking in the sipr0n discord decap-commission channel: https://discord.gg/qyne7GZk https://discord.gg/qyne7GZk