diff --git a/papers/doc/7-systems/ym2610.md b/papers/doc/7-systems/ym2610.md
index dbe8b6a54..f557ea23d 100644
--- a/papers/doc/7-systems/ym2610.md
+++ b/papers/doc/7-systems/ym2610.md
@@ -4,6 +4,8 @@ originally an arcade board, but SNK shortly adapted it to a rather expensive vid
 
 its soundchip is a 3-in-1: FM, YM2149 (AY-3-8910 clone) and ADPCM in a single package!
 
+YM2610B variant is YM2610 with 2 extra FM channels, it's mainly used at some 90s Taito Arcade hardwares.
+
 # effects
 
 - `10xy`: set LFO parameters.