Multibyte or not?

Hello all,

at the mysql-admin list I found a posting that says a non-multibyte built of
the database would be faster than a multibyte one. My question is - do I
always need a multibyte built if I plan to access the db with jdbc or do i
only need it if the data is non-ascii? i know that java uses unicode but does
that really matter unless I want to enter non-ascii letters?

actually this came to my mind when I was in search for some tuning hints. I
don't think this is the right place to ask this (would 'psql-admin' be that?)
- but maybe one of you had similar problems?
I am doing a lot of checking and inserting at runtime. while the java thread
holds ~38Mb (~500Mb) it uses only 1.7% CPU (~900Hz). postgresql uses less
than 4Mb at more than 90% CPU. I already doubled the effective cache size to
be '2000' but that did not change anything.

I wonder if the postgres would be faster if it would use more RAM. or is this
the bottle neck's end (unless I get a better CPU)?

thank you
Chantal