In rdpLRANDR.c I found the refresh rate is 50Hz. And I can get 50Hz from xrandr command.
Screen 0: minimum 64 x 64, current 1280 x 1024, maximum 8192 x 8192
rdp0 connected 1280x1024+0+0 0mm x 0mm
1280x1024 50.00*+
But when I test glxgears command with __GL_SYNC_TO_VBLANK=1 or vblank_mode=1. The frame rate is not 50Hz.
Running synchronized to the vertical refresh. The framerate should be
approximately the same as the monitor refresh rate.
46715 frames in 5.0 seconds = 9342.961 FPS