I saw the conversation about the FPGASID project and I’d thought I’d share some work I have been doing regarding SID implementation in FPGA as well.
I purchased a Papilio Pro (http://papilio.cc/index.php?n=Papilio.PapilioPro) board as part of the retrocade synth (http://retrocade.gadgetfactory.net/) a while ago and recently decided to try and find out how many SIDs I could fit into the board if I took everything else out. I ended up with 4 SIDs plus the associated shift registers that I am able to connect right up to my MIDIBox MB6582. I can even drive both real SIDs and the FPGA versions from the same signals from the MIDIBox in order to do A/B comparisons.
I am working on designing an interface board to connect the midibox to the papillio pro, it isn’t finished but if anyone is interested it is here: https://upverter.com/LVL1Soundbuilders/32fbede244e1a406/Papillio-Pro-to-Midibox-SID-Interface-PCB/
The papilio pro is open source, the board I am working on is open and I’d be glad to share my file of the 4 sid implementation. I’ll post a link once I decide on the best place to put it.