Lots of small doc tweaks.

Little fixes, little reformats, that sort of stuff.

doc/7-systems/5e01.md

@@ -1,6 +1,6 @@
 # 5E01
 
-a fantasy sound chip created by Euly, based on the Ricoh 2A03, with some improvements:
+a fantasy sound chip created by Euly, based on [the Ricoh 2A03 in the NES](nes.md), with some improvements:
 
 - a 37.5% duty cycle,
 - 32 noise pitches instead of 16, and
@@ -56,7 +56,6 @@ a fantasy sound chip created by Euly, based on the Ricoh 2A03, with some improve
 - `20xx`: **set DPCM frequency.**
   - only works in DPCM mode.
 
-
 ## info
 
 this chip uses the [NES](../4-instrument/nes.md) instrument editor.

doc/7-systems/amiga.md

@@ -45,6 +45,7 @@ this chip uses the [Generic Sample](../4-instrument/sample.md) instrument editor
 - the maximum rate for sample playback is technically 31469Hz but anything higher than 28867Hz will sound glitchy on hardware.
 - sample lengths and loop will be set to an even number.
 - samples can't be longer than 131070.
+- samples must be 8-bit. Furnace handles conversion automatically.
 
 ## chip config
 

doc/7-systems/ga20.md

@@ -6,9 +6,7 @@ the sound chip itself is rather unremarkable, having 8-bit volume and pitch cont
 
 ## effects
 
-none
+this chip has no added effects.
-
-let's be honest. Furnace has too many chips and a great portion of them are sample chips that do the same task: playing back samples.
 
 ## info
 

doc/7-systems/gba.md

@@ -2,7 +2,7 @@
 
 a portable video game console from Nintendo, succeeding the Game Boy.
 
-it adds two stereo sample audio channels which can be used directly ("DMA", left/right) or used in a software mixing driver (most games do this) in order to have multiple voices.
+it starts with the [Game Boy sound hardware](game-boy.md) and adds two stereo sample audio channels which can be used directly ("DMA", hard-panned, usually used as left/right channels) or used in a software mixing driver (most games do this) in order to have multiple voices.
 
 # effects
 
@@ -20,7 +20,6 @@ it features echo and up to 16 voices.
     - put `110x` in the effect column.
     - set volume column to set feedback.
     - don't use the channel for anything else.
-
 - `12xy`: **toggle invert.**
   - `x` left channel.
   - `y` right channel.

doc/7-systems/sms.md

@@ -4,7 +4,7 @@ the SN76489 is a relatively simple sound chip made by Texas Instruments. a deriv
 
 the noise channel's default mode uses only 3 preset frequencies. to use the full range of pitches, one can enable a mode which matches the frequency of square wave channel 3. in addition, periodic noise mode can be enabled to create a "thin pulse" tone that sounds four octaves lower than the square wave channels.
 
-the original iteration of the SN76489 used in the TI-99/4A computer, the SN94624, runs at a clock speed of 447 kHz (NTSC 3.58 MHz pre-divided by 8) and can only produce square waves as low as approximately 110 Hz, or note A2. later versions of the chip (such as the one in the Master System and Genesis) instead have an internal /8 divider and generally run at higher clock rates (such as undivided NTSC 3.58 MHz) to achieve a matching or similar frequency range.
+the original iteration of the SN76489 used in the TI-99/4A computer, the SN94624, runs at a clock speed of 447 kHz and can only produce square waves as low as approximately 110 Hz, or note A2. later versions of the chip (such as the one in the Master System and Genesis) add an internal divide-by-8 stage and generally run at higher system clock rates to achieve a matching or similar frequency range.
 
 ## SN7 versions
 

doc/7-systems/ym2608.md

@@ -1,10 +1,10 @@
 # Yamaha YM2608 (OPNA)
 
-like YM2203, but with twice the FM channels, stereo, an ADPCM channel and built-in drums ("rhythm")!
+like YM2203, but with twice the FM channels, stereo, an ADPCM channel, and 6 channels of built-in drums (the "Rhythm Sound Source")!
 
 it was one of the available sound chips for the NEC PC-88VA and later models of PC-98 series of computers.
 
-the YM2610 (OPNB) and YM2610B chips are very similar to this one, but the built-in drums have been replaced with 6 sample channels.
+the [YM2610 (OPNB)](ym2610.md) and [YM2610B](ym2610b.md) chips are very similar to this one, but in those the rhythm channels become general ADPCM channels and the built-in drum samples are removed.
 
 ## effects
 

doc/7-systems/ym2610.md

@@ -2,7 +2,7 @@
 
 originally an arcade board, but SNK shortly adapted it to a rather expensive video game console with the world's biggest cartridges because some people liked the system so much they wanted a home version of it.
 
-its soundchip is a 4-in-1: 4ch 4-op FM, YM2149 (AY-3-8910 clone) and [2 different format ADPCM](https://wiki.neogeodev.org/index.php?title=ADPCM) in a single package!
+its soundchip is a 4-in-1: 4ch 4-op FM, YM2149 (an AY-3-8910 clone) and [2 different formats of ADPCM](https://wiki.neogeodev.org/index.php?title=ADPCM) in a single package!
 
 ## effects
 

doc/7-systems/ym2610b.md

@@ -1,7 +1,6 @@
 # Taito Arcade/Yamaha YM2610B
 
-YM2610B is basically YM2610 with 2 extra FM channels used at some 90s Taito arcade hardware.
+YM2610B is basically a derivative of [YM2610](ym2610.md) with 2 extra FM channels, used in some 90s Taito arcade hardware. it is backward compatible with the original chip.
-it is backward compatible with the original chip.
 
 ## effects