SFX Expander programming and VICE

Hi All,

I'd like to play with the SFX Expander cartridge programming. I don't have
such a cartridge (well, currently), so for now I have the only option to
use an emulator.  It seems VICE can emulate it.  However, if I try, nothing
happens (no sound is produced, emulated SID is working, so it's not a
general sound problem of the emulator/my OS, or such).

Accordint to http://www.floodgap.com/retrobits/ckb/secret/sfx.html
I have to do only this:

     ; load x with register, a with data for that register

        stx $df40               ; select ym3526 register
        nop
        nop
        nop
        nop                     ; wait 12 cycles for register select
        sta $df50               ; write to it
        ldx #4
lup     dex
        nop
        bne lup                 ; wait 36 cycles to do the next write

I've tried vice both with YM3526 and 3812 selected for emulation. My code is
tested on PC (of course the x86 assembly version not the 6510), when 388h
and 389h is used (AdLib ports) since AdLib (and SoundBlasters also contains)
uses the 3812, so I am quite sure that the YM3812 programming itself should
be correct and it should produce sound.  Also, as far I as understand, 3526
should work like 3812 "just" lacking OPL2 features.

Does anybody have experience in SFX Expander programming and/or VICE related
emulation issues (if there is any) about this topic?

Or maybe I should do more than just the included assembly fragment, like
initialization or so?

Any example program (with source if possible) is also welcome, so I can
check if it works at all using VICE as emulator.

Thanks a lot in advance,

- Gábor

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