Roland switchable SDE/SRV330, running SDX330 port

SRV & SDE share common PCB, with one extra DSP on SRV. Switch mod pages RAM/ROM banks, and toggles second DSP bypass circuit. SDX has some hardware changes, and a couple of extra control lines to the analogue side (dry cut and mute). Modified SDX OS can run on SDE/SRV hardware. Shown here replacing SRV mode. 3-way switch would be much more work - 2 banks is maximum possible with existing ROM/RAM footprints.