ATi blobs are nasty unfortunately - they have vastly improved but still have issues
A couple of things you can try
#1
Code:
cat /proc/mtrr
reg00: base=0x000000000 ( 0MB), size= 2048MB, count=1: write-back
reg01: base=0x080000000 ( 2048MB), size= 1024MB, count=1: write-back
reg02: base=0x0c0000000 ( 3072MB), size= 512MB, count=1: write-back
reg03: base=0x100000000 ( 4096MB), size= 4096MB, count=1: write-back
reg04: base=0x200000000 ( 8192MB), size= 512MB, count=1: write-back
Generally you shouldn't have any un-cachable entries.
#2
Code:
newx() { DISPLAY=:1.0; xinit $* -- :1; }; newx /opt/HoN/hon.sh
and redo those ingame tests
#3 disable the composite xorg extension