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, chip supports 256kB of sample RAM and can hold up to 127 samples at once.

# effects

- `20xx`: **set chip output rate.**
# config flags
## 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:

- 1 MHz, resulting sample rate is 7576 Hz
- 1.056 MHz, resulting sample rate is 8000 Hz
- 1.02 MHz, resulting sample rate is 7727 Hz
- 1.193 MHz, resulting sample rate is 9038 Hz
- 0.89 MHz, resulting sample rate is 6742 Hz
- 0.875 MHz, resulting sample rate is 6629 Hz
- 0.9375 MHz  resulting sample rate is 7102 Hz
- 1.5 MHz, resulting sample rate is 11364 Hz
- 1.79 MHz, resulting sample rate is 13561 Hz
- 2 MHz, resulting sample rate is 15152 Hz 
- 2.112 MHz, resulting sample rate is 16000 Hz
- 3 MHz, resulting sample rate is 22728 Hz
- 3.58 MHz, resulting sample rate is 27122 Hz
- 4 MHz, resulting sample rate is 30304 Hz
- 4.224 MHz resulting sample rate is 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.