My X850 is having a reality crisis

Hey all
For some weird reason, 3dmark, MemStatus 2.5, ATI tray tools all tell me I have a 512mb X850XTPE, while ATI drivers and DXDiag tell me I have a 256mb X850XTPE.
I have set up monitoring graphics in ATI tray tools, and it CLEARLY shows that my VRAM usage often surpasses 256mb. What the heck is going on here?
For some weird reason, 3dmark, MemStatus 2.5, ATI tray tools all tell me I have a 512mb X850XTPE, while ATI drivers and DXDiag tell me I have a 256mb X850XTPE.
I have set up monitoring graphics in ATI tray tools, and it CLEARLY shows that my VRAM usage often surpasses 256mb. What the heck is going on here?