If no one answers your first question, then you'll have to go to
www.tyan.com and look up your specific mobo's page. Then download the owner's manual and look it up. I'm looking at that page now and it shows the manual is available in .pdf format at the bottom of the page. Download Acrobat Reader from the same page first if you don't already have it. Here's your mobo page, which I believe is the Tyan Trinity 400 (S1854):
http://www.tyan.com/products/html/trinity400_p.html
The voltage may not be adjustable, and this may prevent you for overclocking very high. Generally speaking Tyan's are not made for overclocking, but are very stable boards.
You might want to search the forums for threads on this too.