Good Evening from Aurora, CO everyone,

I am trying to find the answer to this question:
I own a System76 computer (panp6) with m740tu(n)/m760tu(n)/w7x0tun mother board as far as I can determine with Linux dmidecode (ha ha and on a sticker underneath) in conjunction w/ an Itel T4200 dual core. My question is, do I have to stick with socket pga 478 cpu upgrades similar to the T4200, or does my mother board (see former) have an LGA 775 socket thus enabling me to install a much higher CPU? I realize I can't go with an I5/7, but if my motherboard is dual socket I could go with something pre 10 extreme. Also, could I determine this myself? And how?
Thanks for your help,
Richard