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Re: Old keyboards

Posted on 2023-07-13, 06:19

Model F capacitive buckling spring board with modern minimalist 84-key SSK layout, made with the original tooling brought out of retirement. Is that from https://www.modelfkeyboards.com/? I had no idea that the original Model F tooling was involved. I was pleased to see that they finally introduced …

Re: MartyPC

Posted on 2023-07-12, 08:48

in PC Emulation
I am thinking about a software frontend in the future for lower-spec machines, but you won't have the debugger. Ah, then no chance for a simpler console/TUI-based debugger interface? I was wondering if that could make things easier to implement, maybe through one of those curses libraries that can …

Re: Emulating CGA Snow

Posted on 2023-07-12, 08:11

in PC Emulation
So in VGA terms, basically the value read from plane 1 (the attribute plane) gets replaced with the value that's read from RAM, while the other byte (from plane 0, which is the character byte) gets read normally? On these particular cycles yes, that seems to be what's happening. The alternate case …

Re: Emulating CGA Snow

Posted on 2023-07-11, 20:25

in PC Emulation
Oh, missed this: I surmise that the character bytes for the displayed text in video memory being copied generate the initial variety of different colors within the snow immediately below; after we proceed past that the snow becomes either white or green. I am not sure where the green comes from. The …

Re: Emulating CGA Snow

Posted on 2023-07-11, 18:17

in PC Emulation
Parts like the intro, the dot starfield, the Delorean, and the IBM vectorballs should have absolutely no snow, since they're not running in 80-column (+HRES) mode.

Re: MartyPC

Posted on 2023-07-09, 22:37

in PC Emulation
That also works for the PCjr and Tandy 1000, which happen to have 90-degree-increment shifts (relative to the IBM CGA) in mode 6. Is that all that is needed? I would have thought there would be some differences in the multiplexer, too... There could very well be - to get that figured out, we'd need …

Re: MartyPC

Posted on 2023-07-09, 21:43

in PC Emulation
You can roll the hue through 360 degrees and nothing looks quite right. Somehow a phase adjustment is intrinsically different, but I haven't worked out the math as to why. I think I get it, now that I've had a look at v0.1.3. I must've misconstrued which part of the signal processing chain this …

Re: MartyPC

Posted on 2023-07-06, 06:23

in PC Emulation
Joysticks were never really my thing on the PC; I don't even have one for my daily driver - for joystick games in DOSBox I just use the keymapper to map host keystrokes to emulated joystick events. As far as I know that's also SDL functionality, but may be easier to implement without it... say using …

Re: MartyPC

Posted on 2023-07-05, 16:09

in PC Emulation
Here's my blogpost about MartyPC . I digress as usual, but I thought I'd bring up some more examples (games from the old days) that other emulators don't really deal with 100%, but this one does. This also raised the question: what are your thoughts about adding joystick support via keymapping of …

Re: MartyPC

Posted on 2023-07-05, 06:53

in PC Emulation
Excellent work on the latest release, and the improved composite emulation! Any plans to introduce early/late-type CGA composite selection, given the latter? ;) I'm seeing an issue with v0.1.2 on my machine - this doesn't seem to happen with the web player, so I'm wondering if it's been fixed since …

Re: Did anyone ever use a 320x175 mode in EGA?

Posted on 2023-06-29, 19:49

I seem to remember that one version of Paperboy did this in EGA mode. Or maybe it was 320x350, which should also be interesting (basically mode 10h at half the dot clock). This would require a real EGA monitor, though, something which seems to be very rare these days. Or a multisync one. It'll work …

Re: Emulating Area5150

Posted on 2023-06-28, 20:03

in PC Emulation
What's the difference betweeen bit 0 and bit 1 both being set and bit 0 being set without bit 1 being set? It calls one "interlace sync raster scan mode" and the other "interlace sync and video raster scan mode". What's the difference between those two? It might be related to the weird behaviour …

Re: CGA/EGA "pixel-doubling" of 320-pixel wide modes

Posted on 2023-06-27, 19:45

I disagree. It's fake, simply because it's not complying to the NTSC standard. Non-interlaced operation isn't being specified/supported, so it's a form of hack. Because, it's not as if the monitor suddenly stops to interlace the signal. It still does. This pseudo "progressive" scan is just a …

Re: CGA/EGA "pixel-doubling" of 320-pixel wide modes

Posted on 2023-06-27, 19:25

Thanks, and you're right. I've tweaked it further; how about these? Unfortunately, I have only a couple of late 90s/early 2000s VGA monitors, but no EGA, so I need to rely on photo/video references alone which is far from optimal. Also, even on 4k trying to replicate the triad dot pattern is a …

Re: CGA/EGA "pixel-doubling" of 320-pixel wide modes

Posted on 2023-06-27, 05:40

There's nothing "fake" about CGA's progressive scan. It's non-interlaced, hence progressive. You may point out that it's half the resolution you'd get from 'standard' NTSC progressive scan, but then again it's also double the frame rate. And progressive-scan NTSC was certainly not 'standard' at the …

Re: Emulating Area5150

Posted on 2023-06-26, 21:35

in PC Emulation
Nice, looking way better now. :) Vertically perhaps it could still use a tiny upwards nudge, but that's hard to tell- it might just be that the canvas is slightly cut off at the bottom? (there's an ~8-pixel strip of background that sticks around after I hit 'Run'.) For what it's worth: in terms of …

Re: Emulating Area5150

Posted on 2023-06-26, 18:31

in PC Emulation
I think the key to getting all the various graphics modes properly centered is to pin the hsync start position along with having the virtual monitor hsync after a fixed period, ignoring the programmed sync width. My video_debug mode generates a 912x262 output frame so you can see all the time spent …

Re: Emulating Area5150

Posted on 2023-06-26, 18:13

in PC Emulation
The general idea is pretty much as Scali put it. It's one reason why the MODE command has those ",r"/",l" parameters to shift the screen horizontally by changing the hsync position, and why quite a few early CGA games also offered such a setting; you could never be quite sure what a particular …

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