Eric, > Pointers/links please! if in doubt, use either 'google' or 'wikipedia' (fast becoming my favourite place for info) http://en.wikipedia.org/wiki/MOS_Technology_SID http://perso.orange.fr/silvertouch/VSID.htm (FPGA filter) http://myhdl.jandecaluwe.com/doku.php/projects:phoenixsid_65x81 (hardware filter) Paul