There’s now a custom firmware for the OSSC that extends the functionality of the test patterns. There’s a bunch of excellent features, but the one that’s most intriguing to me are the refresh rate tests:
“Many classic game consoles do not operate exactly at standard 59.94/60/50Hz refresh rate, especially if typical 50/60Hz modifications have been applied on them. Moreover, there are systems that use refresh rates way outside what is common today. The tests help identifying how well a monitor can handle these off-spec rates by displaying a moving checkerboard box at non-standard refresh rates. In ideal case, the monitor is able to sync each mode and display it without any judder resulting from internal framerate conversion.“
If you’d like to try it out, all you’ll need to do is image a MicroSD card (2GB or smaller recommended) the same way you would with a Raspberry Pi image (SDFormatter and Win32DiskImager).
Please remember that the OSSC isn’t firmware-locked, so you can revert to an older version if you’d like: http://junkerhq.net/xrgb/index.php?title=OSSC_display_test_suite