diff --git a/papers/doc/7-systems/ym2610.md b/papers/doc/7-systems/ym2610.md
index dbe8b6a5..7eb66eb3 100644
--- a/papers/doc/7-systems/ym2610.md
+++ b/papers/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 3-in-1: FM, YM2149 (AY-3-8910 clone) and ADPCM in a single package!
+its soundchip is a 3-in-1: FM, YM2149 (AY-3-8910 clone) and 2 different format ADPCM in a single package!
 
 # effects
 
diff --git a/papers/doc/7-systems/ym2610b.md b/papers/doc/7-systems/ym2610b.md
index da4f542d..2b2e5fea 100644
--- a/papers/doc/7-systems/ym2610b.md
+++ b/papers/doc/7-systems/ym2610b.md
@@ -1,6 +1,6 @@
 # Taito Arcade/Yamaha YM2610B
 
-YM2610B is basically YM2610 with 2 extra FM channels used at some 90s Taito Arcade hardwares.
+YM2610B is basically YM2610 with 2 extra FM channels used at some 90s Taito Arcade hardwares, it's backward compatible with non-B chip.
 
 # effects