Well, I finally have an IBM 5150.

[Fallo]

I had gotten a 5150 off of Ebay last week, and it arrived today. All seems fine with it so far. I put my CGA card in it, set the motherboard switches for 40x25 text, and connected the video to an old 9" TV with an RF modulator.

When I powered it on, I got a blinking cursor on the TV screen, and after a few seconds, Cassette BASIC started. I typed a few programs, then tried booting Troll's Tale. Works perfectly, as compared to the split-screen mess you get running it on VGA.

I then booted a DOS disk and tried Dig Dug and Shamus. We had a discussion a while ago about games on VGA vs. real CGA, so I was eager to see how they would behave. Dig Dug works more-or-less the same, but I found that it turns the video off between levels to hide the drawing of the screen (on VGA, you see it). Shamus is slower and choppier on real CGA (on VGA, it's really fast).

However, the color trimmer cap needs adjusting. I could not get it to display the red/green/yellow palette, only the cyan/magenta/white one. Also, some of the background colors in graphics mode were way off. For example, in BASIC, typing COLOR 9,1 should give you a light blue background, but I get a shade of pink. The ancient, 1970s TV set I was using also produced a lot of interference and fuzz, and the colors wouldn't stay. They kept fading in and out. I'll try it with a better TV.

 

[Trixter]

The composite color palette(s) do not match the RGB palette. The first eight colors are usually the same or very close, then the latter eight differ significantly.

 

[Fallo]

The composite color palette(s) do not match the RGB palette. The first eight colors are usually the same or very close, then the latter eight differ significantly.

Yeah, I know they're not quite the same as the RGB colors. The composite colors are supposed to look something like this:

http://en.wikipedia.org/wiki/File:CGA-NTSC-colors.png

The ones I get are very different. As I said, I get pink instead of blue. Cyan is a light blue and magenta is light red. Instead of the red/green/yellow, I get more-or-less the same colors as with the cyan/magenta/white palette, but with a light blue-green instead of white.

I also tried the interlace mode BASIC program that we discussed before, and it does fill up the whole screen on a composite display, although it's flickery.

 

[tezza]

Well done on getting one of these "classic" machines.

My 5150 has a CGA card with a composite output. I should hook it up to a composite monitor one of these days just to see what the output looks like!

Having a TV/Composite monitor sitting up on the box rather than a geniune IBM CGA Monitor would just look so wrong though! :D

Tez

 

[Fallo]

Well done on getting one of these "classic" machines.

The Ebay bidders were less aggressive than usual with this one, possibly because it didn't have any cards except the floppy controller. I have an AST Six-Pak that I'll put in, but it has some loose memory chips that need to be straightened out first.

My 5150 has a CGA card with a composite output. I should hook it up to a composite monitor one of these days just to see what the output looks like!

Try it and see if you get the correct colors, or if they're off like mine are. I don't have a RGB monitor, so I have to use the composite output.

Having a TV/Composite monitor sitting up on the box rather than a geniune IBM CGA Monitor would just look so wrong though! :D

Nonetheless, that's what people did before the 5153 was introduced. They used composite monitors or third-party RGB displays. I saw a picture once of Bill Gates in about 1982 showing some kind of PC demo to the editor of Byte Magazine, and he had a composite monitor sitting on the computer.

 

[Fallo]

UPDATE: Today, I connected the 5150 to a better TV. The picture is now clear and interference-free, but I'm not getting any color at all. The weird colors on the other TV were apparently just the result of interference (since they kept fading in and out), so I'll have to adjust the trimmer cap.