I just got KnoppMyth working yesterday and have a a AMD Athlon 64 3800+ X2 dual-core processor in it.

As I understand, MythTV is excellent with making the best use out of dual-core processors (multi-threading).

However, is any initial set up needed to get the best use out of a dual-core or Myth handles all that automatically?

Also, the same question goes for 64-bit (vs 32 bit) processors. Does Myth optimize automatically?

Thanks everyone

Use of multiple CPUs will happen automatically since the OS takes care of that all by itself.

Use of the 64 bit capability will not, since the software is all built for 32bit operations. A 64 bit version is on Cecil's road map for the next generation of KnoppMyth. On the other hand any gain you'd get from this would be far less significant.