8x300 firmware for the aforementioned harddisk controller got dumped. Looks sane, too:
00000000: E036            jmp  0036h
00000002: E029            jmp  0029h
00000004: B021            nzt  liv0,1,01h
00000006: B704            nzt  liv7,0,04h
00000008: B324            nzt  liv3,1,04h
0000000A: 1781            move liv7,4,r1
0000000C: 8109            xec  r1,09h
0000000E: 8119            xec  r1,19h
00000010: E004            jmp  0004h
00000012: C700            xmit 00h,ivl

There's another 8x300 disassembler out there -- http://amigan.1emu.net/releases/Dis8X305.readme -- could be useful.