I'm not getting through. It's one card, one system, two monitors, set
up identically. Where is the beat coming from?
That's really weird.
I once had two monitors connected to different PCs running at almost
the same rate (the difference was about 10hz in the horizintal rate, so
about 0.01hz in the vertical rate) and the beating was clearly visible
as a vertical discontinuity (vertical retrace in the other monitor) that
slowly migrated up the screen of one of the monitors
I solved the problem by rearranging my desktop to have a pc case
between the two monitors.
Not possible. It's my work system (I went to LCD long ago). There is
no setting other than 60, 75, or 85Hz (at least at 1280x1024).
ultimately it comes down to the rate of the pixel clock in the crtc
if they're both phase-locked to the same source (logic suggests that
this would be the case) then it should be possible to phase-lock the
horizontal, and vertical scans also by using the same base pixel
clock, horizontal total and vertical total settings.
doing that requires that the maker of the video driver exposes the
CRTC registers to the OS and that you get in behind the scenes and
tweak them. (In windows this means special software or editing the
registry, in linux it's xvidtune and adding modelines to the /etc/x11/xorg.conf file)
not easly, may or may not be possible.
if it were me I'd (after investigating and rejecting a software based fix)
get a 600mmx600mm piece of .4mm steel sheet (eg pc case side panel)
and wedge that between the monitors and see if it helps, if it only
helps a little I'd try two, mu-metal, or thicker.
seing as it's at work I'd complain to my immediate boss, IT, and or HR,
that's it's causing "stress"