News of a cool new technique for actual delay(as opposed to a software effecting using spare voices)  that runs exclusively on the older 6581 sounds chip.

He explains:

The Norwegian composer Geir Tjelta has introduced a new trick for the SID-chip: realtime delay. The output of the third channel of the SID can be recorded, and by delaying the playback of the sample on the “virtual” fourth channel, you get a subtle echo. This routine doesn’t use much CPU-time either. A nice and elegant trick. Get the exe and mp3 here.

He then teases the following:

Geir also programs an editor together with GRG, Sid Duzz It, which according to the rumours will include this echo effect along with extensive MIDI support in the next version.

via More Soundchip Hacking: Realtime SID delay « CHIPFLIP.