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Re: Emulating Area5150

Posted on 2023-05-25, 22:05

in PC Emulation
Ah yes, VileR and myself are the OG overscan/border fundamentalists! (*knocks on random people's doors*) "Hello, do you have a moment to talk about our Lord and Savior, the Border Area?" :D I haven't been 100% satisfied with my CGA composite simulation and wanted to improve it a bit before making a …

Re: Emulating Area5150

Posted on 2023-05-25, 21:58

in PC Emulation
It didn't start out that way, I kept trying to derive effective resolution from the CRTC registers and I constantly ran into issues in 8088MPH dealing with the logic for it. I think I saw this very advice from either you or Scali on here, and I had some good input from one of the oldschool CPC guys …

Re: Emulating Area5150

Posted on 2023-05-25, 08:42

in PC Emulation
That's massive. Hats off! Some other emulators have been getting close, but yours does appear to be the first to pull off complete accuracy in all sections. What's more, it correctly represents what is seen on the monitor, by rendering a fixed region - overscan included - and allowing the emulated …

Re: No CRT Emulation? Why!?

Posted on 2023-05-08, 18:18

in PC Emulation
Hm, how about RetroArch's own ffmpeg core then? Viable? My thoughts are along the lines of taking arbitrary video sources of the 'correct' resolution (say, real hardware RGB captures), applying a shader on playback, then capturing that using OBS or somesuch.

Re: CGA "phantom" vsyncs: glitch-testing the 6845 CRTC

Posted on 2023-05-08, 06:04

I wasn't sure how the C64 scrolling talk was relevant here (was it meant to go in the "scrolling over the edge" thread?), but it was intriguing to read up on that "VSP crash". Apparently the underlying cause is similar to the 6845's vsync glitch: electro-mechanical factors along the line may cause …

Re: VGA behavior when "scrolling over the edge"

Posted on 2023-05-06, 20:47

Exactly - good rundown. The only practical issue isn't related to programming differences between the EGA and VGA, but to the vertical refresh rate: the same modes that operate at 60Hz on EGA are 70Hz on VGA. So if your code targets one of them, the other one will either show tearing or incorrect …

Re: VGA behavior when "scrolling over the edge"

Posted on 2023-05-06, 08:15

I didn't think VGA had the "panning" features that EGA does? I'm actually not sure how that works - is it a value you change that points to the beginning of the "screen" in the video memory? When scrolling vertically that's pretty much how it works, yes: you set the start address for the displayed …

Re: No CRT Emulation? Why!?

Posted on 2023-05-03, 16:15

in PC Emulation
Yeah, it'd be nice to have these shaders accessible outside of a specific library's "walled garden" so to speak. Someone has ported crt-royale from libretro to ReShade (https://github.com/akgunter/crt-royale-reshade), so I suppose this should be possible. Haven't tested it yet, but I've been …

CGA "phantom" vsyncs: glitch-testing the 6845 CRTC

Posted on 2023-05-03, 09:19

A little while ago I came across a strange little CGA issue, where certain writes to the 6845 CRTC registers were causing unexplained visual glitches. This didn't seem to be documented anywhere else, and looking into it led me down an interesting rabbit hole. I ended up detailing my findings over …

Re: Why no 720x480 bitmap resolution in VGA?

Posted on 2023-04-27, 19:55

in Milliways
It always seemed to me that 720x480 (or well, 360x240) would provide better emulation of 200-line CGA/EGA modes, if you centered the active area within the slightly larger frame: - Vertical refresh rate would be 60 Hz, the same as 'native' 200-line (15.7KHz) modes - You'd have a more authentic …

Re: xyWords - New DOS game for XT/CGA

Posted on 2023-04-27, 16:14

in Milliways
I was mucking around with with this as a concept and it actually needs the dithered images tweaked to match a composite palette think about what they did with the 8088mph pictures.. At the very least it is possible but would take a tremendous piece of work to pull this off and then fool QB into …

Re: xyWords - New DOS game for XT/CGA

Posted on 2023-04-15, 09:58

in Milliways
I don't know if this solves all of the problem but I haven't seen it crash since I made the change. Nice! Can confirm, all is well on the 5160 now. I played through a few puzzles in succession, had my progress saved and everything, so I think it's safe to say that there are no other issues. What's …

Re: xyWords - New DOS game for XT/CGA

Posted on 2023-04-14, 23:09

in Milliways
Edit: I've been a QB user for many years, but I've spent most of the time on vintage systems (mainly ATs, 286/386/486). So far, I've never encountered such a problem. When I ran QB on an XT a few years ago, QB simply used the installed 8087 silently. Otherwise, before the 8087 was installed, it …

Re: xyWords - New DOS game for XT/CGA

Posted on 2023-04-14, 21:55

in Milliways
Oh yeah... since the above makeshift "patch" has allowed it to run on my XT, here are those CGA CRT photos 😀 Filename xyXT1.jpg File size 157.53 KiB Views 338 views Filename xyXT2.jpg File size 183.25 KiB Views 338 views Filename xyXT3.jpg File size 193.46 KiB Views 338 views Filename xyXT4.jpg …

Re: xyWords - New DOS game for XT/CGA

Posted on 2023-04-14, 21:25

in Milliways
Update on this one: I ran it on a generic turbo-xt 8088/640K and did not get this problem. I might take a look at that timer code anyway, I recall making some changes after debugging an emulator (on a handheld). For now, I found a bit of a clue (and a workaround). I managed to reproduce it in …

Re: xyWords - New DOS game for XT/CGA

Posted on 2023-04-14, 10:34

in Milliways
Well done! I would love to see photos of it running on original hardware XT/286, CGA.. I was hoping to do that, but... 20230414_125911.jpg ...I get this error (at the same address) whenever I start any puzzle. This is on a 640K IBM 5160 with CGA and XTIDE, running the full version off a 2GB CF card …

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