Hi Micah,
Thanks for checking this out for me. I did try playing with maxgartsize before, but have just tried again, with the same results, as follows:
I tried lowering maxgartsize to 128 using the proper aticonfig tool as root, and this hasn't changed the problem: I can still allocate an 8192x8160 resource of float1's, but not an 8192x8161 one. Note that I can allocate two 8192x7000 resources of float1's, so I can use most of the memory of the card, if I use multiple resources.
I also tried raising maxgartsize to 512, given as the upper limit in "aticonfig -h". However, when I did this I got the following in /var/log/Xorg.0.log:
(**) fglrx(0): Illegal ATI GART size: 512 MB, acceptable range: 64 MB - 255 MB.
(**) fglrx(0): ATI GART size: 255 MB
(II) fglrx(0): [pcie] 261120 kB allocated
and, not surprisingly, got exactly the same results as before.
Perhaps you could ask one of the fglrx people to take a look sometime in case they can suggest a fix?
Thanks again,
Steven.