I found this information was surprisingly tricky to nail down but finally found a link. I needed to download an SDK where it was important that I downloaded the correct architecture, whether or not my Macbook was 32-bit or 64-bit. After googling around for a bit I finally found a forum post which linked to a site which linked to the page I’m going to share here. It’s a table of all of the different processors Apple puts into their machines and their architecture.
I hope everyone finds this helpful:
http://support.apple.com/kb/ht3696