First post, by clb
Hey all,
I got a bit curious to find out more about 70Hz video mode compatibility of different LCD displays, and how prevalent the "well known" Dell 2007 frameskip is, or isn't, with other displays.
The other thread Good 4:3 LCD Monitor has been discussing monitors, and one of the aspects was 70Hz capability, and the known effect of frameskipping 70Hz down to 60Hz.
In that thread, I wrote a test program 70HZ.EXE, which can be used to visually eyeball if a particular display is frameskipping 70Hz down to 60Hz. Maybe we could crowdsource results from a couple of random different LCD panels that people are using, both old and new.
Test scheme:
1. Download https://github.com/juj/crt_terminator/raw/ref … OS/bin/70HZ.zip to your vintage PC.
2. Run 70HZ.EXE
3. Observe whether both conditions take place:
a) White blocks with numbers 0,1,2,3,4,5,6 appear with equal temporal frequency of flicker, and for example none of the blocks are absent some of the time, or all the time. (there is some amount of flicker here for those sensitive to it, apologies for that)
b) the left-to-right panning animations on the blocks below the text are smooth, and not juddering.
If these conditions are ok, then the current display is likely not frameskipping, but is displaying all the 70Hz frames.
If you are not sure, you can press space bar to toggle the tested video mode between 60 Hz and 70 Hz output. If both modes look identically smooth, then the display is likely showing full 70Hz. The 60 Hz output should definitely be smooth on grounds of both a) and b) above. (when toggling to 60hz, there may be garbage pixels shown at bottom of screen, those can be ignored)
Then report your findings as either:
- OK (passed conditions a and b above, i.e. displays 70Hz without frameskipping)
- Frameskip (displayed the test picture, but did not pass a or b, i.e. likely frameskips down to 60Hz)
- No sync (did not even display the test video mode, so cannot sync to 70Hz video)
I'll start:
Year | Display name | Results | Display native resolution-----+-----------------------------+-----------+--------------------------2003 | Fujitsu-Siemens P19-1 | OK | 1280x10242004 | Sony SDM-X73 | OK | 1280x10242006 | Dell 2007FPB | Frameskip | 1600x12002006 | Dell 2007WFP | Frameskip | 1680x10502009 | BenQ ET-0029-B /G2412HD | OK | 1920x10802009 | Acer V223w | OK | 1680x10502014 | BenQ BL3201PT | No sync | 3840x21602014 | HP EliteDisplay E241 | No sync | 1920x12002022 | Philips Brilliance 252B9/00 | OK | 1920x12002022 | ASUS ProArt PA248QV | OK | 1920x1200
You can see here an example video of how the test appears on Dell 2007 display that exhibits the frameskip: https://youtu.be/p95zPv9kDTk : ASUS PA248QV (left) against Dell 2007FPB (right) (recorded as 60 Hz, though the absent digit 5 in the test can be clearly seen in that recording, which shows the frameskip taking place on the Dell)
When testing, please do not use any video scaler or converter, like OSSC, RetroTink, or other, as that can skew the result (or if you do, please explicitly mention).
