asterisk users - Mar 2005 - ways to get more accuracy from ztdummy

Greetings!

I have a FreeBSD 5.3 running on Intel SR1300 (dual xeon 2.6, scsi) server,
with ztdummy.ko driver as timing source for asterisk.

The typical output from zttest is:
$ zttest
Opened pseudo zap interface, measuring accuracy...
[..skip..]
--- Results after 192 passes ---
Best: 99.987793 -- Worst: 98.266602


But when i listening MOH, it's quality is not very good. It is slightly
choppy.
(Asterisk _uses_ ztdummy, without ztdummy MOH sound is more awful)

Is there any techniques for getting more accuracy?
May be some software or hardware tricks?

Thanks for any help.
-- 
Aleksey Skripka
.masterhost