VOGONS


First post, by dr.zeissler

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Hi,

this thread is for all the CGA-Lovers out there. It is intended to be a collection of interesting informations
and software-recommendations for users with XT-Computers and CGA graphics-cards/chips.

I currently use my Schneider EuroPC which is upgraded to a NecV20 and has a build in CGA/MDA Chip.

Most software used the standard cga-palette in that time, but there were some titles that let's you choose
the palette or changes it in game.

Thx
Doc

Last edited by dr.zeissler on 2017-05-16, 12:50. Edited 2 times in total.

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Reply 3 of 60, by xjas

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California Games changes the palette *mid screen* to show >4 colors at once.

7722-california-games-dos-screenshot-footbag-cga-more-color-mode.gif

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Reply 4 of 60, by dr.zeissler

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but that are ntsc color artefacts when using composite mode.
therefore I only have a schneider europc i'll have to stick to cga-rgb 🙁

But this game looks awesome on cga (alternative palette)

https://www.youtube.com/watch?v=CR0oAjhXBcE&t=130s

more colors, mean lower res (160x100) or textmode.

Retro-Gamer 😀 ...on different machines

Reply 5 of 60, by dr.zeissler

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Does someone know a tool where I can watch cga-images and switch between the palettes?
otherwise I have to use paintshop-pro and convert the images to the cga-palette I want.

Retro-Gamer 😀 ...on different machines

Reply 6 of 60, by MMaximus

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From memory here are a few games I remember playing which used the "green red yellow" palette:

Burger Time
Digger
Styx
Pitstop II
Defender of the Crown
The Three Stooges
Targhan

I'm certain you can change the palette in Crazy Cars by Titus (probably by pressing F1 or another function key) so it's likely you can do the same with other Titus games (Galactic Conqueror, Off Shore Warrior, Fire & Forget...)

I've seen the Rick Dangerous video and that's not how I remember it to look on my CGA XT back in the day 😕 . On the video it looks somehow composite-like...

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Reply 7 of 60, by derSammler

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dr.zeissler wrote:

but that are ntsc color artefacts when using composite mode.
therefore I only have a schneider europc i'll have to stick to cga-rgb 🙁

No, that's plain RGBI CGA. It uses a very clever trick to do so, which sadly only works on the original PC/XT due to tight timing requirements.

Composite mode looks like this:
137228-california-games-dos-screenshot-the-footbag-event-cga-with.png

Reply 8 of 60, by dr.zeissler

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MMaximus wrote:

I've seen the Rick Dangerous video and that's not how I remember it to look on my CGA XT back in the day 😕 . On the video it looks somehow composite-like...

He used an EuroPC with an Amstrad EGA Monitor in CGA mode.

Retro-Gamer 😀 ...on different machines

Reply 9 of 60, by dr.zeissler

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derSammler wrote:

No, that's plain RGBI CGA. It uses a very clever trick to do so, which sadly only works on the original PC/XT due to tight timing requirements.

Thx for making that clear! I'll check this on my EuroPC.

http://www.oldskool.org/shrines/lbd/graphics/
The only game I ever ran that used some of the above tricks to do some primitive copper effects was California Games (1987). Its video selection menu had the normal CGA 4-color mode, but it also had a mysterious CGA "more-color" mode. The "more-color" mode was only used in two places: The title screen and the hackeysack portion. Why? Because those screens had a clear horizontal division of a graphic on the top half of the screen and one on the bottom half. The "more-color" mode would switch palettes at a certain scanline to display one set of colors on the top graphic, and a different set of colors on the bottom. As you can imagine, this was unnervingly time-critical, and self-programming vertical-retrace interrupts took too long (hey, you needed all the speed you could get) on a 4.77MHz machine, so this trick only worked on the one machine that they could hard-code the values into: The original IBM with an original CGA. I always used to think that this mode didn't do anything until I brought it over to my friend's house and saw it work. It worked pretty well, oddly enough. Maybe I was just easy to impress. 😀

Last edited by dr.zeissler on 2017-05-14, 11:39. Edited 1 time in total.

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Reply 10 of 60, by dr.zeissler

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Some games used the "red" instead of "mangenta" (afair galaxian)

http://www.oldskool.org/shrines/lbd/graphics/
CGA (Computer Graphics Adapter) always struck me as finicky. The video memory layout was interlaced, which means that the first 8K was every even-numbered scanline and the last 8K was every odd-numbered scanline. Plus, there were 192 bytes unused at the end of both 8K sections, so that became annoying to skip as well. Finally, you had one of two fixed palettes of nasty, ugly colors (cyan, magenta, and white; or red, green, and yellow) to choose from. While some of the best artists could deal with four colors adequately, the crappy color set usually disgusted the user. Well, I quickly found out that by fiddling with the video registers, I could get an unadvertised (to my manuals, anyway) color palette that seemed to combine the two palettes. The resulting 4-color palette had black, white, cyan, and red--much nicer. I'm sure this palette was advertised somewhere because some game I had used it, which is what got me sending random bytes to the video ports in the first place.

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Reply 11 of 60, by dr.zeissler

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Here is some SceneStuff:

00061483.png
http://www.pouet.net/prod.php?which=61483

00064406.png
http://www.pouet.net/prod.php?which=64406

00063627.png
http://www.pouet.net/prod.php?which=63627

00058526.jpg
http://www.pouet.net/prod.php?which=58526

00068386.gif
http://www.pouet.net/prod.php?which=68386

00013722.png
http://www.pouet.net/prod.php?which=13722

00063591.png
http://www.pouet.net/prod.php?which=63591

00065371.gif
http://www.pouet.net/prod.php?which=65371
Fantastic but not working on my cga-rgb EuroPC

Retro-Gamer 😀 ...on different machines

Reply 13 of 60, by Jo22

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The last demo doesn't work on my PC/XT (8088, CGA).

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 14 of 60, by dr.zeissler

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8088mph does not work on rgb-cga machines, only on composit. That's way it's not working on my EuroPC too.

Btw. this russian? converter tool is nice, but it has no option for changing the palette, it seems only support the standard-cga-palette.

Attachments

  • Filename
    img_cga2.rar
    File size
    304.89 KiB
    Downloads
    108 downloads
    File license
    Fair use/fair dealing exception

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Reply 17 of 60, by dr.zeissler

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PC-Paint 3.1 can be used in CGA and there you can choose for every possible palette.

The "cga-convert-program" above generates rle/cga binary files from bmp-bitmaps, but I can't use/display them afterwards,
so I will go for Paintshop-Pro 5.x instead, because I can't find a progam that is optimized for cga and theire palettes.

Retro-Gamer 😀 ...on different machines

Reply 18 of 60, by reenigne

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dr.zeissler wrote:

Does someone know a tool where I can watch cga-images and switch between the palettes?
otherwise I have to use paintshop-pro and convert the images to the cga-palette I want.

I wrote one, which you can get at http://www.reenigne.org/misc/cgaart.zip. It's not finished yet and there are some bugs, but it can accomplish a wide range of CGA conversion tasks, including this one. After unzipping, run "cgaart name_of_input_mage.png" from the command line. For this purpose, a pixel-exact 320x200, 640x200 or 640x400 image (e.g. DOSBox screenshot) should work best. The first time it starts up it will take a minute or so to do anything but it will start up immediately on subsequent runs.

Change the Diffusion settings to 0 and the mode and palette registers to the ones that were used when the screenshot is created. The program should then have recreated the contents of the CGA memory when the image was made. Next, turn off matching by clicking the "Match" button so that it is unpressed. Now changing the mode and palette registers will not modify the CGA memory but instead show what the recreated CGA memory contents would look like with the new register values.

Reply 19 of 60, by dr.zeissler

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Sounds good, hopefully it will run on my iMac with wine. The img_cga2.rar is quite nice with gui, but it's laking some features like
changing the cga-pal and the output of an usefull image-format like gif, pcx or lbm.

Retro-Gamer 😀 ...on different machines