Today I tested full duplex roundtrip latency ( audio in -> csound -> 
audio out ) with csound5 on linux. I used a hard disk recorder as the 
source and destination with one side going through the computer, and the 
other loopbacked through a cable. The latency on the csound side was 1.5 
ms. This is excellent news, but I believe it could be made lower as full 
duplex was working without break up down to -b4 -B8, so that means most 
of that latency is from my soundcard and linux. I have read that the 
latest realtime kernel patches are quite an improvement over the one I 
was using and should get latency down to 0.6 ms, so I will report again 
once I have the latest 2.6.14-realtime kernel. Hardware is AMD3000+, 
Delta 66, running Gentoo 2.6.13desktop-preempt.

On the whole, awesome news for real time fx with csound!

Iain