radeon driver and 120 hz displays

[snkt]

I have a Samsung SyncMaster 2233RZ monitor which can do real 120 hz. When using the fglrx driver with my Radeon 4850, i can choose between 60, 100, 110 and 120 hz. However, when using the radeon driver, i can only select 60 hz.

Here's the xrandr output:

Screen 0: minimum 320 x 200, current 1680 x 1050, maximum 1680 x 1680
HDMI-0 disconnected (normal left inverted right x axis y axis)
VGA-0 disconnected (normal left inverted right x axis y axis)
DVI-0 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 478mm x 300mm
1680x1050 59.9*+

I'm using Ubuntu 9.10.

[DanL]

Create a mode line using cvt:

cvt 1680 1050 120Hz

It should return something like:

# 1680x1050 119.89 Hz (CVT) hsync: 135.24 kHz; pclk: 313.75 MHz
Modeline "1680x1050_120.00"  313.75  1680 1816 2000 2320  1050 1053 1059 1128 -hsync +vsync

Now add the mode using xrandr:

xrandr --newmode "1680x1050_120.00"  313.75  1680 1816 2000 2320  1050 1053 1059 1128 -hsync +vsync

Change to the new mode:

xrandr --output DVI-0 --mode 1680x1050_120.00

[snkt]

Thank you for your replay DanL. I had to add 'xrandr --addmode DVI-0 "1680x1050_120.00"' after the newmode because otherwise xrandr complained about an unknown mode.

It didn't work tho :-( The mode changed successfully, but my monitor went black and i got an wrong mode message and had to restart :-(

[snkt]

Update:

KMS wasn't enabled by default. Enabling it brought me all the modes fglrx detected :-)

Works quite well so far.. Desktop is smooth, ioq3 and smc both run fine. Got about 200fps in q3 with a 1680x1050 res and high gfx settings. Smc seems a bit choppy tho..

[legume]

Thank you for your replay DanL. I had to add 'xrandr --addmode DVI-0 "1680x1050_120.00"' after the newmode because otherwise xrandr complained about an unknown mode.

It didn't work tho :-( The mode changed successfully, but my monitor went black and i got an wrong mode message and had to restart :-(

Just for reference cvt -r may have worked. The -r is for reduced blanking so the pixclock is lower.

bash-3.2$ cvt -r 1680 1050 120
# 1680x1050 119.86 Hz (CVT) hsync: 133.29 kHz; pclk: 245.25 MHz
Modeline "1680x1050R"  245.25  1680 1728 1760 1840  1050 1053 1059 1112 +hsync -vsync

You'll need a recent cvt (part of xorg) as IIRC the older versions would only do -r if the refresh rate was 60Hz.