noob question zbuffer depth

[Davros]

just wondered why nvidia doesnt support a 32bit zbuffer just 24bit
while ati does

hey i said it was a noob question

[Graham]

I'd expect their silicon is designed for optimal 24/8 depth/stencil setup. Adding support for 32 bit would probably mean more transistors, for what can be argued as a not worthwhile tradeoff.
Ati may well have a design that accommodates 32bit without significant extra complexity. One of the hardware guys can probably shoot me down on this though :P

[Davros]

could it be that they both have a 32bit buffer but in nvidia chips its hardwired to be 24z 8stencil
while ati cards are free to allocate it any way they want
a bit like they way old voodoo cards had a fixed amount of memory set aside for z buffer + textures and now cards dont...