furnace/doc/7-systems/msm6295.md

# OKI MSM6295

an upgrade from 6258 - it provides 4 ADPCM channels, at max 32 KHz (still no variable pitch though). between late '80s and late '90s, it was one of the most common, if not _the_ most common soundchip used in arcade machines (Capcom, Toaplan, Kaneko, Atari, Tecmo, the list can go on and on...). Without bankswitching, the chip supports 256kB of sample RAM and can hold up to 127 samples at once.

# effects

- `20xx`: **set chip output rate.**
  
# chip config
## chip clock rates
like MSM6258, MSM295 is an extremely basic ADPCM sound codec. it has no variable frequency rate, it depends on clock rate of a chip itself. Furnace supports following rates:

| clock rate         | sampling rate |
|--------------------|---------------|
| 1 MHz              | 7576 Hz       |
| 1.02 MHz           | 7727 Hz       |
| 1.056 MHz          | 8000 Hz       |
| 1.193 MHz          | 9038 Hz       |
| 0.89 MHz           | 6742 Hz       |
| 0.875 MHz          | 6629 Hz       |
| 0.9375 MHz         | 7102 Hz       |
| 1.5 MHz            | 11364 Hz      |
| 1.79 MHz           | 13561 Hz      |
| 2 MHz              | 15152Hz       |
| 2.112 MHz          | 16000 Hz      |
| 3 MHz              | 22728 Hz      |
| 3.58 MHz           | 27122 Hz      |
| 4 MHz              | 30304 Hz      |
| 4.224 MHz          | 32000 Hz      |

## chip clock divisor

MSM6295 clock rate could be divided by 132 (resulting sample rates above), or by 165. To get a clock rate using divisor of 165, formula is clock rate (in Hz) / 165. Example: 1 MHz MSM6295 in 165 divisor mode results in output rate of 6060 Hz.