Force 50Hz mode on 60Hz monitor

RetroArch Linux devices
#1

hello, my monitor doesn’t support 50Hz, than C64 and Amiga games doesn’t run good: screen tearing while scrolling.

$ xrandr 
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 16384 x 16384
VGA-1 connected primary 1280x1024+0+0 (normal left inverted right x axis y axis) 338mm x 270mm
   1280x1024     60.02*+  75.02  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   640x480       75.00    72.81    66.67    59.94  
   720x400       70.08  
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)

Can i solve?

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#2

If your monitor doesn’t support 50 Hz, RetroArch can’t do anything about it.

#3

It can basically work via a custom modeline, like this:

xrandr --newmode “768x576_50” 29.25 768 864 948 1084 576 582 592 625 -hsync -vsync

xrandr --addmode VGA-0 “768x576_50”

I haven’t been able to get 50 Hz via VGA on LCDs, only via HDMI.

2 Likes
#4

thanks. i have tried that tricks. refresh seems ok but resolution is distorted, elongated:

i have used those commands: $ cvt 1280 1024 50 # 1280x1024 49.84 Hz (CVT 1.31M4) hsync: 52.68 kHz; pclk: 88.50 MHz Modeline “1280x1024_50.00” 88.50 1280 1352 1480 1680 1024 1027 1034 1057 -hsync +vsync

$ xrandr --newmode pippo 88.50 1280 1352 1480 1680 1024 1027 1034 1057 -hsync +vsync

$ xrandr --addmode VGA-1 pippo

$ xrandr --output VGA-1 --mode pippo

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#5

Just a friendly warning: If the monitor does not properly support that Hz, as in even if it does manage to work with the custom created mode, it is possible that the monitor will gradually and eventually go bad.

My last CRT monitor started to go narrower the more I used 50Hz with it, so that even with the horizontal adjustment maxed and with regular supported Hzs, it was no longer possible to fill the screen properly.

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#6

If it has HDMI it supports 50hz for sure. 720x576 @ 50 hz is a standard HDMI mode.

1 Like