I have made a little video of the MB909 sequencer hooked up with the 9090 boards. combined you have the greatest TR-909 clone (that's just my opinion because I put a lot of time in it ).
I am using the NXP LPC1769 based MBHP_CORE_LPC17 module from MidiBox. Thorsten has done a great job with the MidiBox Sequencer V4 (SD card, USB, OSC....).? The PCB, that you see in this video, is my TR909-looking user interface design.
the quality is bad, but you'll have at least a feeling of how my sequencer will be.