For successful overclocks, you need a realtime-scanning LCD -- one that syncs horizontal scan rate, the panel scanrate to signal scanrate. Not all panels refresh in perfect sync to signal scanrate.
These are often called "Lagless Mode" or "Instant Mode" (the setting in BenQ monitors) which does the nearly-bufferless subrefresh latency like a CRT, where the only meaningful monitor latency effectively is video cable micropacketization (e.g. DIsplayPort packets) and GtG pixel response. Only a tiny rolling line buffer window is used in these modes, mainly for the purpose of display cable micropacket dejittering and for extremely minor processing overheads (e.g. scaling, overdrive, etc) that only relies on lookbehind buffers, without the need for the monitor to fully framebuffer a refresh cycle before refreshing the LCD panel as seen in high speed videos at www.blurbusters.com/scanout
Frameskipping can occur if you are pushing the edge, try 200 Hz or 190 Hz, keep decreasing until it passes frameskipping tests at www.testufo.com/frameskipping
.... Make sure you're doing that test correctly (test at non-overclocked Hz, and don't test multimonitor) before you test overclock. So make sure you have a successful frameskip-free 144Hz before you test frameskipping at overclocks.
There are many reasons why things don't overclock:
- More buffers add overclock bottlenecks (non-realtime scan)
- More electronics add overclock bottlenecks (bottleneck in additional chips)
- More menu UIs add overclock bottlenecks (bottleneck in OSD graphics overlaying chips)
- More processing/smart logic add overclock bottlenecks (bigger processors in monitors)
- Advanced processing (HDR / FALD / etc) add overclock bottlenecks (more chips that are weak links)
- Fixed Hz add overclock bottlenecks (monitors that can run at any Hz in 1Hz increments from 60Hz-144Hz are easier to overclock)
- Scan conversion add overclock bottlenecks (panels that convert signal scanrate to a fixed panel
- Arbitrary undefeatable range checks ("OUT OF RANGE' without a dismiss-hack like this thread) add overclock bottlenecks
TL;DR; Overclocks are only as strong as the weak link
Which means more advanced monitors are often less overclockable....ironically.
Which is why "dumber" panels are sometimes easier to overclock than newer/smarter/fully featured panels. Like that old 60Hz laptop display that overclocked to 180Hz. Or the very thin-electronics-layered Zisworks 4K120Hz chinese panel that successfully overclocks to 480Hz at http://www.blurbusters.com/480hz
The fewer weak links, the better. And you definitely need it to be in instant mode (whether by default, or as a menu setting), because that means the panel is synchronized to the signal, and you're overclocking at the signal level.
If you successfully overclocked to 205 Hz but there is frameskipping,
(1) Make sure you test 144 Hz and fix your frameskipping verification process (e.g. no multimonitor malfunction)
(2) Then try again. If fail, keep decreasing by 5Hz or 10Hz until frameskipping disappears.
Even on my XL2720Z, my 220Hz sometimes go into a frameskipping loop about 25% of the time. I just repeat (reset the S-Switch, or switch back-fourth 144Hz <-> 220Hz) and the frameskipping disappears. It's more reliable if I only overclock to 200Hz or 210Hz. The weak link could be the existing VBI processing loop that runs between refresh cycles, and you might be hitting the threshold limits, causing frameskipping when monitor-processing margins become too tight.
Each monitor is different due to different manufacturing tolerances, much like some CPUs can only overclock by 25% and other CPUs can overclock more to 50%. We get odd overclocking problems that are often unique, or model-dependant, or cable-dependant, or timings-formula dependant (CVT, CVT-Reduced, Manual, etc). Many monitors have overclock caps (e.g. 165 Hz overclock caps) but I love it when overclocking is uncapped -- like the discovery of the BenQ overclocks.
The fastest I've seen a 144Hz 1080p BenQ overclock to is approximately 240Hz-250Hz with an older BenQ XL2720Z with one of those lower version numbers (probably due to less intra-blanking processing overheads). Combined with custom hand-edited Manual Porches (if you 100% understand exactly what a Vertical Back Porch does, and what the purpose of a Horizontal Front Porch is, etc). Colors are rather severely degraded at that point though.
For better colors and for easier overclocking by monitor overclocking novices is, roughly 190-220Hz range. Keep backing down by 5Hz or 10Hz until colors starts to pop again & frameskipping properly settles Temper your expectations accordingly, you are going to have problems otherwise.