Pukka had been working long on the disassembler, and we were finally able to get first version of it integrated with the emulator. Below is a simple partial disassembly of Tetris audio mixer VBL, executed from Xcode debugger command prompt:

Although the disassembler itself still has some minor quirks to fix, there were some interesting bits we found about the Tetris mixer code in this disassembly:

• Unlike Sound Driver, which has 4-channel mixer, Tetris uses a 6-channel mixer
• The audio is downsampled from 22256 Hz to 11128 Hz by writing each sampled byte twice (the $7000(A6) at 00030C18 is supposed to be 2(A6) in disassembly)
• The division of summed samples by 6 is done by pre-calculated lookup table (which has 6×256 = 1536 entries)
• The pitch of channels is controlled by directly writing the fixed-point pitch into mixer code at addi.l instructions from 30BAA to 30BC8