# 10 bit DACs on Radeon 8500 and Mac Classic OS **URL:** \ **Category:** Uncategorized\ **Created:** [July 15, 2003, 12:20am UTC](https://psychtoolbox.discourse.group/t/10-bit-dacs-on-radeon-8500-and-mac-classic-os/1180 "2003-07-15T00:20:33Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![michaelsilver2003](https://avatars.discourse-cdn.com/v4/letter/m/5fc32e/32.png) [@michaelsilver2003](https://psychtoolbox.discourse.group/u/michaelsilver2003)\ **Post date:** [July 15, 2003, 12:20am UTC](https://psychtoolbox.discourse.group/t/10-bit-dacs-on-radeon-8500-and-mac-classic-os/1180/1 "2003-07-15T00:20:33Z")
Hello, I am running the Psychophysics Toolbox on a PowerMac G4, ATI Radeon 8500 AGP card, Matlab 5.2.0, in Classic mode (OS9 emulator running within OS X). When I execute SCREEN(windowPtr,'Gamma',gamma,10) I get the error message Warning: SCREENGamma: cscSetGamma error -17. Couldn't set gamma. The command LoadClut(windowPtr,clut,0,10) produces Error -17 in SCREEN 'Gamma'. Screen 1, bits 10 According to ScreenTest, the DACs are only 8 bit. ClutTest produces SetGamma error -17 everytime it tries to set a 10 bit gamma table. Since I am running in Classic mode, I have installed the OS9 graphics drivers from ATI (including the most recent update posted October 2002 and updated February 2003). Does anyone know how I can use 10 bit DACs with the Radeon 8500 and the Mac Classic operating system? Thanks in advance. Cheers, Michael Silver