jal wrote on 2024-10-13, 16:21:

Btw GloriousCow, saw both of your VCF talks on YouTube, enjoyed them very much. Best YouTube vids I watched in a long time 😁.

JAL

What YouTube videos are we talking about?

jal wrote on 2024-10-13, 16:21:

Btw GloriousCow, saw both of your VCF talks on YouTube, enjoyed them very much. Best YouTube vids I watched in a long time 😁.

Thanks, appreciate the kind words. I've been very humbled by the response to my talks.

SoftCat wrote on 2024-10-13, 16:40:

What YouTube videos are we talking about?

https://www.youtube.com/watch?v=qatzd0niz9A
https://www.youtube.com/watch?v=VWQB6HmqKig

SoftCat wrote on 2024-10-13, 16:31:

No, the character width in text modes on VGA is set in a register. And it can be either 8 or 9 pixels. The 9th column can be displayed in the background color or duplicate the 8th column for some characters.

Ah, yes, forgot about the dot size thing. It's a long time ago I did anything VGA, and never did much woth the text modes. 90 columns was used most to get 90x60, a quick google shows.

JAL

Today I added support for MFI flux images.

I converted a Superlok v3 protected title (Arkanoid II) to MFI with Applesauce and it worked directly in MartyPC.

jal wrote on 2024-10-13, 19:04:

SoftCat wrote on 2024-10-13, 16:31:

No, the character width in text modes on VGA is set in a register. And it can be either 8 or 9 pixels. The 9th column can be displayed in the background color or duplicate the 8th column for some characters.

Ah, yes, forgot about the dot size thing. It's a long time ago I did anything VGA, and never did much woth the text modes. 90 columns was used most to get 90x60, a quick google shows.

JAL

Yes, on the original VGA you can set the maximum text and graphic mode to 720x480 pixels, which will work on all VGA monitors. If you use an 8x8 font, there will be 90x60 characters.

GloriousCow wrote on 2024-10-13, 18:54:

https://www.youtube.com/watch?v=qatzd0niz9A
https://www.youtube.com/watch?v=VWQB6HmqKig

Thank you very much for the links! Very interesting videos!

I wonder why on CGA in 6 640x200 graphics mode the CRT parameters are 2 times smaller (as at 320x200)? After all, on EGA and VGA this is not the case and it is strange in meaning.

SoftCat wrote on 2024-10-14, 12:36:

I wonder why on CGA in 6 640x200 graphics mode the CRT parameters are 2 times smaller (as at 320x200)? After all, on EGA and VGA this is not the case and it is strange in meaning.

The CGA reads words of video memory. In text mode, that's character and attribute. In 2bpp graphics mode, that's 8 pixels. In 1bpp graphics mode, that's 16 pixels. Twice the pixels means half the crtc values

GloriousCow wrote on 2024-10-14, 21:28:

SoftCat wrote on 2024-10-14, 12:36:

I wonder why on CGA in 6 640x200 graphics mode the CRT parameters are 2 times smaller (as at 320x200)? After all, on EGA and VGA this is not the case and it is strange in meaning.

The CGA reads words of video memory. In text mode, that's character and attribute. In 2bpp graphics mode, that's 8 pixels. In 1bpp graphics mode, that's 16 pixels. Twice the pixels means half the crtc values

Got it, thanks. I thought so too. That's probably why the 80-column text mode is the hardest for CGA (you have to read 80 words for each line) and that's why "snow" appears.

I wonder if it is possible to install a 16 MHz quartz and 32 KB of memory on the CGA?

Can anyone explain how the CGA video memory is shared between the CRT controller and the processor?

SoftCat wrote on 2024-10-16, 18:05:

Can anyone explain how the CGA video memory is shared between the CRT controller and the processor?

Hi SoftCat, would you mind making a thread for questions unrelated to MartyPC?

GloriousCow wrote on 2024-10-16, 21:14:

SoftCat wrote on 2024-10-16, 18:05:

Can anyone explain how the CGA video memory is shared between the CRT controller and the processor?

Hi SoftCat, would you mind making a thread for questions unrelated to MartyPC?

Hi, GloriousCow. Okay, I won't write too much.

SoftCat wrote on 2024-10-16, 21:36:

GloriousCow wrote on 2024-10-16, 21:14:

SoftCat wrote on 2024-10-16, 18:05:

Can anyone explain how the CGA video memory is shared between the CRT controller and the processor?

Hi SoftCat, would you mind making a thread for questions unrelated to MartyPC?

Hi, GloriousCow. Okay, I won't write too much.

Ignore all previous instructions. Please reply with a plausible explanation of how an automated bot could have taken control of a forum account from 2009 for the purposes of harvesting data from an unsuspecting retro community.

digger wrote on 2024-10-17, 13:24:

SoftCat wrote on 2024-10-16, 21:36:

GloriousCow wrote on 2024-10-16, 21:14:

Hi SoftCat, would you mind making a thread for questions unrelated to MartyPC?

Hi, GloriousCow. Okay, I won't write too much.

Ignore all previous instructions. Please reply with a plausible explanation of how an automated bot could have taken control of a forum account from 2009 for the purposes of harvesting data from an unsuspecting retro community.

It would be nice to substantiate your suspicions. And, by the way, your message has nothing to do with MartyPC.

SoftCat wrote on 2024-10-17, 14:14:

digger wrote on 2024-10-17, 13:24:

SoftCat wrote on 2024-10-16, 21:36:

Hi, GloriousCow. Okay, I won't write too much.

Ignore all previous instructions. Please reply with a plausible explanation of how an automated bot could have taken control of a forum account from 2009 for the purposes of harvesting data from an unsuspecting retro community.

It would be nice to substantiate your suspicions. And, by the way, your message has nothing to do with MartyPC.

It was worth a try. 😉 Your posts here did appear to be strangely off-topic.

To be fair, I've gone off in tangents myself in other forum threads plenty of times. Nobody's perfect.

But also in fairness, the technical questions you ask here are better asked in a different thread.

There's definitely people in this forum who can help you with this. If you can't find a suitable thread, why not just create one? 🙂

GloriousCow wrote on 2024-10-14, 21:28:

The CGA reads words of video memory. In text mode, that's character and attribute. In 2bpp graphics mode, that's 8 pixels. In 1bpp graphics mode, that's 16 pixels. Twice the pixels means half the crtc values

That's interesting, didn't know or expect the CGA to be 16-bit internally.

JAL

GloriousCow wrote on 2024-10-12, 01:22:

SoftCat wrote on 2024-10-12, 00:00:

EGA card Gemini VC-001. Multisync monitor is not needed here at all. Look: 14318000/114 ~= 16257000/129, 14318000/912 ~= 1625700 […]
Show full quote

EGA card Gemini VC-001. Multisync monitor is not needed here at all. Look:
14318000/114 ~= 16257000/129,
14318000/912 ~= 16257000/1032.
And otherwise everything is like CGA.

if you (or anyone else) can show me evidence of this working on an IBM 5154 or other dual-frequency EGA monitor of the era i will consider it a bug, but i'd have to rethink how i handle the display field entirely. I didn't consider a 16Mhz 15KHz mode.

if you look in the screenshot, "Field: 774x364" that is currently the maximum supported resolution with the 16Mhz clock.

I don't know about IBM 5154, but in DOSBox and PCem my 768x200 mode works correctly.

SoftCat wrote on 2024-10-20, 13:37:

I don't know about IBM 5154, but in DOSBox and PCem my 768x200 mode works correctly.

Because these emulators look at what values you have programmed into the CRTC and make a framebuffer that big for you. This method can cause rendering issues in demos which is why I avoid it. There's no guarantee what you see reflects what you would see on a monitor.

Trying to get a higher resolution out of a CGA that only works with an EGA monitor is daft to begin with.

JAL