Problems with set ColorDepth 8bit in solaris10X86

Hi friends, i need to run a program in 8bit colordepth in solaris10X86.
this is my pc:
core2E7300
MotherBoard:ASUS P5QL
VideoCard:ASUS9600GT
systemsolaris10X86 U6

first install driver NV 173.xx, then i try to correct "DefaultDepth 24" to "DefaultDepth 8"in xorg.conf ,but it seems no use. then i use /usr/X11/bin/xorgconfig to make a new one, and it's the same result.

Anybody know that's why? And i can set 8bit successful in a virtual machine in VirtualBOX3.04,but it's only support 1024768,which i need is 12801024

Did you try setting the color depth with the NVidia Xserver settings GUI (nvidia-settings) and saving the configuration to the xorg.conf file ?

yes,i have done that,but still no use.
some one say it's the problem of video card diver,but he's not sure

Have a look at the X server log files to see if the setting is read and why it is ignored.