What is the max ram on a optiplex G1 with a 450 pentium?

Hi, I am setting up a linux systemon with my old optiplex 450 pentium.

The specs say that 250 mb is the max ram the board can hold. Someone posted on this board that they have a g1 with 512 megabytes of ram.

Can the G1 use 512 megs of ram? If so, do I need to upgrade the bios?