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Re: How hard would it be to make a CGA card?

Posted on 2018-07-23, 13:14

that card looks like the myriad cga/mda/hercules cheap clone cards , no way color means EGA ... not a bad card especially for mda/herc Man.. I thought I had an excuse to buy a scope :) Well... you could still make your own CGA card from scratch, just for fun, even if you don't actually need to! …

Re: How hard would it be to make a CGA card?

Posted on 2018-07-23, 12:36

Oh, root42's answer is better than mine. Actually, looking at that card it seems like there is actually composite generation circuitry on the card, but unpopulated. I wouldn't mind betting that if you populated those resistors, Q1 and P1 the same way as in root42's link that you'd actually get …

Re: How hard would it be to make a CGA card?

Posted on 2018-07-23, 12:32

If you're not bothered about the colours being accurate and you have (or find) a CGA card with an RGBI output, it's a pretty simple circuit to go from RGBI to monochrome composite. I have a card with a 9 pin female output (and an LPT port). not sure what is it.. it drives a monochrome monitor with …

Re: How hard would it be to make a CGA card?

Posted on 2018-07-23, 11:40

I must admit that one of my reasons toward this project is the fact that I own a green monochrome monitor with only composite input. I really want a card to put in my 286 that could drive it :) AFAIK my best option is a CGA card. So, to me, the color part is not a big issue... If you're not …

Re: How hard would it be to make a CGA card?

Posted on 2018-07-23, 11:24

The thing that makes CGA interesting is probably the composite color mode. However this only works in NTSC, so us Europeans are already not that much interested. Hence a CGA card for me would only be interesting if it would already do the composite->NTSC conversion on board, outputting either PAL …

Re: How hard would it be to make a CGA card?

Posted on 2018-07-23, 10:51

There's nothing fundamentally difficult about it - it's just a bunch of discrete logic, a bank of DRAM, the CRTC (which is not hard to find) and a character ROM (which is just a matter of writing the right data to an EEPROM or similar). The schematics are in IBM's documentation and not hard to find. …

Re: Name your machines

Posted on 2018-07-16, 07:49

in Milliways
Mine are all named after characters from Shakespeare plays (and my wifi network is named Stratford): benedict - main laptop prospero - main office desktop machine imogen - media PC falstaff - son's bedroom desktop lysander - old office desktop tybalt - workshop desktop hermione - work laptop …

Re: Best CGA & Hercules games

Posted on 2018-07-06, 10:33

@reenigme - could you provide a link or a screenshot or anything to help me find the game? I have so far found Fire & Forget, Fire & Ice, Return Fire, Astro Fire and a lot of others, but nothing called Fire! The MobyGames page I linked to has some screenshots. It would be against the forum's rules …

Re: IA-32 - does ip even exist?

Posted on 2018-07-06, 09:32

So thinking like this, in essence IP doesn't exist on 32-bit x86 CPU's? The lower 16-bits are stored in memory during any procedure call(int,call), but loads load the full EIP register regardless of the operand size? So IP only exists on the 80286 and earlier(although the 80286 might have 17-bit …

Re: Art of CGA

Posted on 2018-06-25, 22:15

In this thread you suggest that the 40041 is used to decode addresses for the RTC - maybe that's why it was simplest to leave it in for the PC1640. Oh, well found/remembered! I had forgotten all about that. Yes, that makes a lot of sense. It's a sledgehammer to crack a nut but if you've got lots of …

Re: Art of CGA

Posted on 2018-06-25, 13:25

reenigne wrote: I just sent an email to John Elliott - I think if anyone is likely to know, it'd be him. John sent me this link to a newsgroup post by Roland Perry which confirms that, yes, indeed the 40041 in the PC1640 is vestigial - apparently it was just cheaper to build them that way!

Re: Art of CGA

Posted on 2018-06-25, 08:46

I had thought it was just a different ASIC in the 1640, but I might be wrong. Or it's me who's wrong. :) I *think* I've read about this on one of these "old computers" databases. I've just been looking at the schematics, and indeed the PC1640 does seem to have an AMS40041 VDU IC just like the …

Re: Art of CGA

Posted on 2018-06-20, 06:23

I read a bit about its CGA derivative at seasip. I'm not 100% sure, but I think I've heard that the succesor of it, the PC1640 with EGA, still had that custom CGA circuit left intact on the PCB. It was simply disabled somehow.. Anyway, I can't check, because I don't own such a system. I had thought …

Re: Art of CGA

Posted on 2018-06-18, 20:14

Ah, I see. Thanks a lot for explaining this, too! :) I always wondered if that "mode" could be ever used something for. Personally, I'm looking forward a demo, as well. Maybe it could be used for some special effects (moving stars, abstract objects, etc). Yeah, it should be possible to design some …

Re: Art of CGA

Posted on 2018-06-18, 08:26

Thanks a lot for this awesome program, reenigne. May I ask you a question ? It's related to CGA but not completely on-topic: Is it possible to fix an original CGA card's logic to display 4 colours in 640x200 resolution mode ? I don't know where I read this, but from what I remember, IBMs address …

Re: Art of CGA

Posted on 2018-06-18, 07:04

Whats the maximum resolution for the 4 color mode (pink/cyan/black/white) for when i make these? The normal CGA standard for 2bpp mode is 320x200. With a CRTC tweak a slightly larger image (320x204) can be used on IBM CGA cards and some (but not all) clones. CGAArt can handle images of whatever …

Re: Art of CGA

Posted on 2018-06-17, 12:21

You, too ? I can't figure out how to fix my installation of Visual C++. Anytime I try, I fail. :( Sorry about that... I'll have to look into making a proper installer for it that takes care of the prerequisites. In the meantime, https://www.microsoft.com/en-gb/download/details.aspx?id=48145 is the …

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