2022-01-16 06:10:43 +00:00
# General Instrument AY-3-8910
2022-03-26 18:55:20 +00:00
this chip was used in many home computers (ZX Spectrum, MSX, Amstrad CPC, Atari ST, etc.), video game consoles (Intellivision and Vectrex), arcade boards and even slot machines!
2022-01-16 06:10:43 +00:00
2022-10-16 05:53:05 +00:00
it is a 3-channel square/noise/envelope sound generator. the chip's powerful sound comes from the envelope...
2022-01-16 06:10:43 +00:00
2022-10-16 05:53:05 +00:00
the AY-3-8914 variant was used in Intellivision, which is pretty much an AY with 4 level envelope volume per channel and different register format.
2022-03-11 18:30:54 +00:00
2023-09-10 06:44:29 +00:00
Furnace is capable of doing software sample playback on AY-3-8910, where all 3 channels can play 4-bit PCM samples (at the cost of a very high CPU usage).
2023-07-09 12:07:19 +00:00
2023-09-11 00:34:13 +00:00
## effects
2022-01-16 06:10:43 +00:00
2023-06-25 07:05:30 +00:00
- `20xx` : **set channel mode.**
- `0` : square
- `1` : noise
- `2` : square and noise
- `3` : envelope
- `4` : envelope and square
- `5` : envelope and noise
- `6` : envelope and square and noise
- `7` : nothing
- `21xx` : **set noise frequency.** range is `0` to `1F` .
- `22xy` : **set envelope mode.**
- `x` sets the envelope shape:
- `0` : `\___` decay
- `4` : `/___` attack once
- `8` : `\\\\` saw
- `9` : `\___` decay
- `A` : `\/\/` inverse obelisco
- `B` : `\¯¯¯` decay once
- `C` : `////` inverse saw
- `D` : `/¯¯¯` attack
- `E` : `/\/\` obelisco
- `F` : `/___` attack once
2022-01-16 06:10:43 +00:00
- if `y` is 1 then the envelope will affect this channel.
2023-06-25 07:05:30 +00:00
- `23xx` : **set envelope period low byte.**
- `24xx` : **set envelope period high byte.**
- `25xx` : **slide envelope period up.**
- `26xx` : **slide envelope period down.**
- `29xy` : **enable auto-envelope mode.**
2022-01-20 08:23:03 +00:00
- in this mode the envelope period is set to the channel's notes, multiplied by a fraction.
- `x` is the numerator.
- `y` is the denominator.
2022-03-26 18:55:20 +00:00
- if `x` or `y` are 0 this will disable auto-envelope mode.
2023-06-25 07:05:30 +00:00
- `2Exx` : **write to I/O port A.**
2022-03-27 01:55:43 +00:00
- this changes the port's mode to "write". make sure you have connected something to it.
2023-06-25 07:05:30 +00:00
- `2Fxx` : **write to I/O port B.**
2022-10-16 05:53:05 +00:00
- this changes the port's mode to "write". make sure you have connected something to it.
2023-07-09 12:42:48 +00:00
2023-09-10 06:44:29 +00:00
## what is obelisco
2023-08-04 16:11:53 +00:00
2023-09-10 06:44:29 +00:00
it's a name I use for a spiky waveform that starts low.
2023-08-04 16:38:05 +00:00
2023-09-10 06:44:29 +00:00
its origin is a wavetable that comes in DefleMask that happens to be called Obelisco.
2023-08-04 16:11:53 +00:00
2023-07-09 12:42:48 +00:00
## AY derivative modes
2023-07-11 18:27:21 +00:00
AY-3-810 was an absurdly popular chip that was blessed with many third-party clones, licensed or not.
2023-07-09 12:42:48 +00:00
- the AY-3-8914 variant was used in Intellivision, which is pretty much an 8910 with 4 level envelope volume per channel and different register format.
2023-07-14 09:16:36 +00:00
- Yamaha YM2149 was an AY-3-8910 clone released in 1983. it's almost identical to AY with minor differences being: higher hardware envelope step resolution (16 vs 32), half-clock mode when voltage level is low, much stronger DC offset and cleaner, but softer output.
2023-07-09 12:42:48 +00:00
- Sunsoft 5B is YM2149 clone with half-clock mode forced on.
2023-09-10 06:44:29 +00:00
2023-09-11 00:34:13 +00:00
## info
2023-09-10 06:44:29 +00:00
this chip uses the [AY-3-8910 ](../4-instrument/ay8910.md ) instrument editor.
