Merge branch 'master' of https://github.com/tildearrow/furnace into scc

papers/doc/7-systems/ay8910.md

@@ -4,6 +4,8 @@ this chip was used in several home computers (ZX Spectrum, MSX, Amstrad CPC, Ata
 
 the chip's powerful sound comes from the envelope...
 
+AY-3-8914 variant was used in Intellivision, it's basically original AY with 4 level envelope volume per channel and different register format.
+
 # effects
 
 - `20xx`: set channel mode. `xx` may be one of the following:

papers/format.md

@@ -29,6 +29,7 @@ furthermore, an `or reserved` indicates this field is always present, but is res
 
 the format versions are:
 
+- 66: Furnace dev66
 - 65: Furnace dev65
 - 64: Furnace dev64
 - 63: Furnace dev63
@@ -207,7 +208,8 @@ size | description
   1  | continuous vibrato (>=62) or reserved
   1  | broken DAC mode (>=64) or reserved
   1  | one tick cut (>=65) or reserved
-  2  | reserved
+  1  | instrument change allowed during porta (>=66) or reserved
+  1  | reserved
  4?? | pointers to instruments
  4?? | pointers to wavetables
  4?? | pointers to samples