How do 32-bit based servers address > 4 GB of RAM?

I've always been told that 32-bit processors can only address up to 4 GB of RAM (2^32=4,294,967,296 addressable bytes) but now I'm seeing servers that ship with 8 and 12 gigs of RAM.  Curiousity has the best of me and now I'm wanting to know how it's done.  Can it only  be done (In the Intel 32-bit world) with Xeon processors?  Or is it some black magic done by the OS?  I figure an extra bit (figured out by the OS) would double the effective RAM but then I saw a 12 GB server that threw that idea out the window (Hey, 2 bits would work :-\)  I'm giving all the points I have left (My unanswered https://www.experts-exchange.com/questions/20720874/Laptop-DVD-playback-is-blank-on-second-screen.html sucked up the rest of them) but it's just for my curiousity.