Easier Testing & Discovery Of Large Vertical Totals
(Applies to reducing strobe crosstalk
Here's a new Blur Busters tip that will greatly aid in discovery of proper Vertical Totals, if you're using that to reduce strobe crosstalk.
Easy ToastyX CRU Steps
1. Choose a working high-Hz mode (e.g. 240Hz)
2. Lock the dotclock (put radio button on Dotclock, make sure it DOES NOT change)
3. Now lower the refresh rate indirectly
via increasing the vertical total. DO NOT edit refresh rate directly
4. Stop increasing vertical total once the calculated refresh rate fully lowers to near your targeted refresh rate. (It may be fractional, e.g. 180.002Hz or 119.998Hz, do not fix the fraction)
You will have weird VTs (e.g. VT2136 or VT1844) and weird fractional refresh rates (e.g. 124.999Hz or 144.001Hz) but you'll be skipping time-consuming experimentation in trying to find large vertical totals. No more out-of-sync errors*
Explanation why this works more reliably on some panels
With a bit of fiddling, it's possible to keep both Horizontal Scanrate (KHz) and Pixel Clock unmodified while changing refresh rate. That's how VESA Adaptive-Sync and FreeSync works -- scanrate & clock never changes but refresh rate varies by varying the vertical total. We're simply borrowing this latent panel capability (unadvertised), to help discover working large vertical totals for fixed non-VRR refresh rates.
The name of the game is to fiddle with Vertical Total until you create a different compatible refresh rate without
changing Horizontal Scan Rate nor Pixel Clock of a very well-working mode. Say, you've got a good 240Hz mode with a 599.640MHz dotclock (or whatever dotclock your perfectly working 240Hz mode was). Now you want to maintain EXACTLY the same dotclock WHILE lowering your refresh rate.
In ToastyX, you simply lock this maximum dotclock of the maximum perfectly working refresh rate. This can help you find the biggest possible exact working vertical total (at least if the panel is FreeSync compatible) for a fixed refresh rate. It can result in weird vertical totals such as VT2631 or VT1844, usually super-humongous at low refresh rates (e.g. 60Hz) and almost same as vertical resolution at maximum refresh rate (e.g. VT1100 or less for 1080p).
Note: When increasing Vertical Total -- it may be better to focus on only increasing Sync (or Front Porch). Generally, avoid increasing Back Porch. Depending on how the GPU output does it, increasing Back Porch may increase input lag by delaying the beginning of the refresh cycle. This is because Back Porch pads the beginning of a refresh cycle. I understand that FreeSync keeps the porches constant while changing Vertical Sync on the fly. For maximum compatibility with Large Vertical Totals on generic LCD panels, you will probably want to focus on changing "Sync" as the method of increasing Vertical Total
Done. Now you've created the biggest possible vertical total for a specific resolution, to help your strobe crosstalk. By locking to the dotclock of 240Hz, you've maintained the scanout velocity of 240Hz, while lowering your refresh rate. You will get weird Vertical Totals such as VT2379 or VT1644 or VT1328 etc, when you're looking for the biggest possible Vertical Total for a specific exact refresh rate. Weird numbers are normal, but at least they work.
- Faster to find a maximum Vertical Total for a specific refresh rate.
- You don't have to experiment to find those "magic working numbers" anymore!
- You also avoid "out-of-sync" of non-working modes (at least on fully FreeSync-compatible panels*
By keeping dotclock and horizontal scanrate the same -- this can make discovery of working Vertical Totals easier for a desired refresh rate, if you have a need for a Large Vertical Total (e.g. reducing strobe crosstalk
This rapid Vertical Total discovery trick only works very reliably on VRR-compatible panels to create a fixed Hz mode with fast scanout (and when Blur Reduction does not modify scanout velocity). XL2540 is one of the models where Large Vertical Totals successfully reduce strobe crosstalk. Although not officially FreeSync, it has been reported to work with FreeSync VRR when forced to do so via ToastyX CRU (48Hz-240Hz range). As a result, this "rapid Vertical Total discovery trick" significantly simplifies your life.
Remember, this came from Blur Busters.
Credit us please, if you document this timesaving trick elsewhere.