Bug 13638

System Environment:
--------------------------

--Platform:g965

--Architecture(32-bit,64-bit,compatiblity):64bit 

--2D driver:
commit e03bc385e924222d3d5f3c9a8d65e1ef63b858dc

--3D driver:
commit 00e10a1385bfd376f5f45ad94e3543ac87f15de8

--DRM:
commit 7dcaf0cdbb57dcf85aa8798736948c280d3966b2

--Xserver:
commit eab0c4e49015fe96f6d985316f9c5fa28a7eb1fe


--Kernel:
2.6.22-rc5


Bug detailed description:
-------------------------
startx ,run xrontfontdemo , it draw nothing ,and soon hangs the system .
if I turn off the TTM , this case can run normally . this case can run smoothly
on 32bit 965 .


Reproduce steps:
----------------
 run xrotfontdemo



Current result:
----------------
draw nothing and hangs the system 


Expected result:
----------------
run normally