Help running FS-UAE @ 50hz on Linux

[roboamiga]

I have been playing with xrandr and was pleased to find my laptop display seems happy to run at 50hz. I did this by doing the following:

"xrandr --newmode "1024x768_50.00" 52.00 1024 1072 1168 1312 768 771 775 793 -hsync +vsync|xrandr --addmode LVDS1 1024x768_50.00"

"xrandr --addmode LVDS1 1024x768_50.00"

"xrandr --output LVDS1 --mode 1024x768_50.00"

Glx gears then gives around 50fps confirming for me that this seems to work. The problem is that as soon as i launch FS-UAE my display then goes back to 60hz and it takes a reboot to get the display able to change down to 50hz again.

Perhaps someone knows a better way to add this screen mode? I have tried adding it via xorg.conf but what ever changes i make there seem to be ignored. I am running the emulator on PCLinux OS.

[FrodeSolheim]

Hi, it is important to get the display running at 50 Hz for Amiga emulation, so I'll try to help the best I can. Unfortunately, I don't have a clear idea of what's going on. FS-UAE does not attempt to switch screen (refresh) mode at all. -But it does specify video width and height when opening the display via SDL. Perhaps something happens here...

Could you please do the following:
- Switch to your 50 Hz mode (rebooting if necessary), verify with GLXgears.
- Start FS-UAE, press Ctrl+F10 and check what FPS you get (the "SYS" number, not the "EMU" one).
- Shut down FS-UAE and attach FS-UAE.log to a post here (you must zip it or renamed to .txt).

Some other things you can check/answer:
- Does this also happen when FS-UAE is started in windowed mode, or only in fullscreen mode?
- What graphics card / Xorg drivers do you have?
- What window manager are you running? Can you try under another one? Does it help if you disable compositing (if you have that enabled)?

[roboamiga]

Hi Frode, Many thanks for your response. I will try to provide all the information you need..

Graphic chip is a Intel 945GM using intel drivers.
Running KDE4 but have also tried XFCE.
The same thing happens when its started in window mode.
The SYS FPS while running was 60fps.
I tried disabling composting but still the same outcome.

[FrodeSolheim]

It makes no sense that the display mode should change when FS-UAE is opened in windowed mode. SDL_SetVideoMode is simply used to open a window.

As part of the boot procedure, FS-UAE runs "xrandr" without parameters to detect the refresh rate. You haven't got a weird setup where simply running "xrandr" reverts to 60 Hz?

Also, does your monitor "blank" shortly while reverting to 60 Hz (can you visually see the mode change)?

[roboamiga]

Hi,
I have tested again and no simply issuing xrandr does not return the display to the original frame rate.

Here is the glx gears info when the display is run at 50hz, is the drops and rises in frame rate normal?

Running synchronized to the vertical refresh. The framerate should be
approximately the same as the monitor refresh rate.
266 frames in 5.0 seconds = 53.053 FPS
248 frames in 5.0 seconds = 49.501 FPS
198 frames in 5.0 seconds = 39.453 FPS
241 frames in 5.0 seconds = 48.187 FPS
197 frames in 5.0 seconds = 39.352 FPS
214 frames in 5.0 seconds = 42.766 FPS
196 frames in 5.0 seconds = 39.122 FPS
272 frames in 5.0 seconds = 54.291 FPS
221 frames in 5.0 seconds = 44.200 FPS
278 frames in 5.0 seconds = 55.573 FPS
273 frames in 5.0 seconds = 54.539 FPS
209 frames in 5.0 seconds = 41.7 FPS

When run at 60hz is stays fairly consistent..

Running synchronized to the vertical refresh. The framerate should be
approximately the same as the monitor refresh rate.
300 frames in 5.0 seconds = 59.884 FPS
301 frames in 5.0 seconds = 60.125 FPS
301 frames in 5.0 seconds = 60.155 FPS
301 frames in 5.0 seconds = 60.136 FPS
301 frames in 5.0 seconds = 60.136 FPS
301 frames in 5.0 seconds = 60.137 FPS
301 frames in 5.0 seconds = 60.135 FPS
301 frames in 5.0 seconds = 60.133 FPS


Also strangely the display does not `blink` when the frame rate goes back up to 60hz. I was able to add my 50hz mode to xorg.conf and get it to show up in the desktop display menu. I did not have the modeline entered properly before. Still the same situation however when changing display via xrandr or normal desktop menu.

Is is possible that the display is teasing me into thinking its running at 50hz when its not really?

[FrodeSolheim]

Originally Posted by roboamiga

Is is possible that the display is teasing me into thinking its running at 50hz when its not really?

Quite possible. I remember having problems with the nVidia driver, where I could create a "50Hz" mode, but this was really mapped against a 60Hz mode. The driver had a concept of frontend mode and backend mode, and I needed to tweak a bit to get the 50Hz mode to be a real "backend mode" (specifcially, I needed AllowNon60HzDFPModes, http://fengestad.no/fs-uae/50hz-disp...nvidia-drivers). This is not directly relevant, since this was the closed nVidia binary drivers, but there could be similar issues with the driver you're using (?).

glxgears should at least have a stable 50 Hz frame rate (it is *not* normal to get the result you posted). As long as it doesn't, there's no point in trying to run FS-UAE @50 Hz.. :-/