4kx4k pbuffers

I’ve been told ,that some new nvidia graphic cards allow to render offline in a 4096x4096 pbuffer !
Is that true ? What kind of cards allows it too?!
Is the render time a lot slower for this resolution ??

thank you

Yes, 4096x4096 pbuffers work on my GeForce5600 with 256MB. I must disable the second monitor output, though.

I just tested the rendering performance using a GL_RGB pbuffer. I get 27fps with a 4096x4096 pbuffer, and 92fps with a 2048x2048 pbuffer. So, the app is almost entirely fill limited - I wonder why

thanks for your answer.
Have you tried the 4k pbuffer for shadow mapping ?!
if true, does it improve enough the shadows quality ?!
Does it diserve to loose so much cpu time ?!

thank you