sofakng wrote on 2021-07-05, 02:25:
Wow -- thanks for that incredibly detailed information!
Are you upscaling the DOS output resolution (ie. 320x200, 640x480) to the native resolution of 1920x1200?
Can you use an OSSC (or similar) to achieve native resolution so everything looks sharp?
The devil is in the details, as they say . I actually purchased and tested about 5 or 6 digitizers/scalers before I settled on the OSSC and have purchased 3 monitors, before I settled on the Philips 252B9 . One of my objectives is to help other people avoid at least some of the trial and error that I had to go through .
My setup with the OSSC and Philips 252B9 is exclusively used for retro purposes and thus always in 4:3 . The setup is as follows :
a) My monitor is set to 4:3 mode, so it behaves as if its native resolution is 1600x1200 and black bars are visible on each side of the screen (unavoidable in4:3 mode as monitor is 1920x1200)
b) Main retro VGA card for DOS use is a Voodoo 3 3000 with an analogue VGA output connected to the OSSC
c) OSSC is set to line2x mode
d) Point c means that 320x200@70Hz, which is actually line-doubled by the VGA card to 640x400@70Hz on output (all VGA cards do this by default) is line-doubled to 1280x800@70Hz by the OSSC
e) Point c means that 720x400@70Hz (VGA text mode) is line-doubled to 1440x800@70Hz by the OSSC
f) The OSSC cannot distinguish between d and and e (no scaler or monitor can), so sampling mode on the OSSC must be switched accordingly on the OSSC manually (to switch, 2 buttons to press on OSSC remote control if using presets)
g) Point c means that 640x480@60Hz is line-doubled to 1280x960@60Hz by the OSSC
h) Any higher resolution than 640x480 is digitized and passed through as is by the OSSC
i) due to a limitation of the OSSC, it is usually not possible to output 320x200@70Hz (line-doubled by the VGA card to 640x400@70Hz) as 1600x1200@70Hz, because this essentially "overclocks" (runs out of spec) the OSSC and usually generates artefacts on screen, which is why I use d . This is a bit of an over-simplification . I can probably link to a previous that explains it better if I can find it .
j) due to a fundamental limitation of the OSSC, it is not possible to output 640x480@60Hz as 1600x1200@60Hz. This is because the OSSC is a line doubler (multiplier), not a scaler, so only integer multiples of a given resolution are possible on output and output resolution of the OSSC is constrained by the 165MHz limit of its TMDS . This means that 1280x960@60Hz is that the maximum you can from 640x480@60Hz, as 1920x1440@60Hz (line3x) would be higher than the monitor's 1200 line maximum and would also be above 165MHz and thus out of spec for the OSSC (if the OSSC even allowed it).
Due to the above points, the OSSC can only take you part of the way to the monitor's "native" resolution of 1600x1200 (when used in 4:3 mode). The rest of the way is achieved by the monitor's scaler . IMHO, that typically still looks extremely sharp and definitely better than any other alternative when using an LCD monitor . See here for a picture of the monitor/OSSC combo running Doom in my setup : Re: Widescreen monitors and 4:3 aspect ratio compatibility thread
EDIT : Corrected typo