First post, by clb
Hi all,
I recently got an OSSC converter for VGA -> HDMI. Pairing that with my BenQ BL3201PT 32" 4K display. https://www.displayspecifications.com/en/model/df62527
OSSC upscales the signal to proper VGA aspect ratio with 5:6 pixels, which is great. I get pillarboxes on left and right of the 16:9 display, forming a 4:3 output. Sweet!
Since OSSC is a scanline level converter, it does not convert refresh rates. On one of my retro PCs, DOS text mode comes in to OSSC VGA input as
Horizontal refresh: 31.46kHz
Vertical refresh: 70.08 Hz
Mode: 419-p
OSSC detected sampling settings: H. samplerate=2000, H. s.rate frac=.00, H.synclen=237, H.backporch=120, H.active=1600, V.synclen=2, V.backporch=34, V.active=400, Sampling phase=180deg
And what goes out to the HDMI display from OSSC is 1600x1200@70Hz.
To a positive surprise, this was not a problem to BenQ BL3201PT: it happily accepts the 70Hz HDMI input video signal - though it does seem to frame-drop it to the 60hz panel, not actually running the panel at 70 Hz. This does cause visible stuttering in panning motion, well observed in e.g. Supaplex that pans the whole game area as one moves.
That is a small nuisance, but something I can live to accept.
However, big problems start with my other retro computer I recently restored, a MikroMikko 4 TT m326. There is an integrated Paradise video card on the motherboard (and I cannot run an external ISA video card on it looks like, won't boot). As a big surprise, the Paradise card generates a non-standard display mode immediately at boot for DOS text mode. OSSC does pick that signal up with no problems, and identifies it as:
Horizontal refresh: 44.55kHz
Vertical refresh: 87.02 Hz
Mode: 512-p
OSSC detected sampling settings: H. samplerate=800, H. s.rate frac=.00, H.synclen=96, H.backporch=48, H.active=640, V.synclen=2, V.backporch=33, V.active=480, Sampling phase=180deg
But the issue is that my BenQ will not accept that refresh rate, but complains "Out of Range". 🙁
When I plug the VGA input in to the original 14" CRT that came with the computer, it does produce a regular 80x25 VGA text mode at DOS boot, so the computer does produce a proper signal.
Now I'm not sure what to do about this. The options that I am pondering about:
1) Get another VGA->HDMI converter. I do already have this cheap "DeLock" one: https://www.delock.com/produkt/62460/merkmale.html . Unfortunately that does not work at all on either PCs (not for 70Hz or 87 Hz text mode). Do such frame rate converting adapters exist?
2) Get another LCD that supports higher refresh rates, like 120Hz. I actually do have an ASUS gaming display with 144Hz support, but it seems to be very picky with its supported input resolutions, maybe due to being a G-Sync panel, or just due to being a gaming display, or just due to being ASUS. The BenQ BL3201PT is advertised as a "Pro"/Business display, and it seems to be very compatible with input resolutions and refresh rates I have thrown at it: it can take in a 320x240@60Hz HDMI input signal from Raspberry Pi without complaints.
I wonder if I tried a high refresh rate "gaming" display from BenQ (they don't seem to have high refresh rate "pro" displays, high refresh are all gaming oriented), if that might have better success with 87Hz HDMI signal?
Or I wonder if I should try one of those displays that have a 75Hz panel and also take in VGA natively? E.g. https://www.msi.com/Business-Productivity-Mon … 1/Specification . Although that one is just 1920x1080, so it cannot perfectly upsample 320x200 -> 1600x1200. Maybe those might have been designed a bit more with VGA in mind, and would accept the 87 Hz HDMI from OSSC.
Can you recommend what might be good LCD displays for this purpose? Do you know of a great compatible LCD for DOS?
3) I would really like to avoid having to add a CRT. But if there is no LCD based solution possible for 87Hz input, maybe I should just bite it and make room in my apartment for a CRT. That raises the question - what is a good CRT for DOS gaming? I would be looking for one that is large enough to comfortably view, preferably ~19" at least. Is there a CRT display model that is known to be great for DOS? Reading other threads on this topic, Sony Trinitrons seem to be very liked.
I am currently primarily interested in 386 and 486 era, with compatibility with various refresh rates for demo viewing, though supporting higher VESA resolutions would certainly be a bonus. I don't mind seeing the pixels, I like them.
Thanks for any tips you might have!