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 # Cybernoid
+
+My motivation was to really push the MAME AY8910 emu code, as the Apple
+Mockingboard music (Skyfox, Ultima) wasn't really exercising it that
+hard.
+
+So as a little R&D proj, I thought I'd convert Dave Rogers' Spectrum
+128 Cybernoid routine (written in 1988).
+
+Here's a summary of how I did it:
+. I got cybernoid.ay from
+http://www.worldofspectrum.org/projectay/gdmusic.htm
+. Split it into bin's with AYSplitR
+. Disassembled with Inkland's dz80w (www.inkland.org)
+. I wrote 6502 macros to replace the z80 opcodes
+. For cybernoid, I hand converted the z80 code to 6502 (using the
+macros)
+. I added a few extension to AppleWin's debugger to help debug the 6502
+code (ACME symbol loading & ZP pointer support).
+
+I use Skyfox's MB detection routine.
+
+The Z80 regs are emulated with zero-page memory locations $F0..$F8
+The playback routine is very inefficient, as it:
+. saves the ZP memory
+. restores the Z80 regs
+. runs the IRQ handler
+. saves the Z80 regs
+. restores the ZP memory
+
+This allows playback to work simultaneously with Applesoft & ProDOS. If
+DOS3.3 doesn't disable IRQs around disk I/O, then it won't work on a
+real Apple (under DOS3.3), but it'll still work on an emulator :-)
+
+I profiled the IRQ handler and IIRC, it takes about 20% of the frame on
+average. This is poor, but the code can easily be optimised. Remember
+this was really just a proof of concept.
+
+After this, I wrote a python script to do the Z80->6502, and quickly
+converted Cybernoid-II.
+
+Currently playback on real h/w produces noisy renditions of the tunes. I
+have replaced my AY-register update routine with the slower one used by Skyfox
+which gives better but not perfect results.
+
+Tom
+25 March 2006