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CGA card saved from being scrapped

Roland Huisman

Veteran Member
Joined
Mar 24, 2011
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The Netherlands
I found this poor little board in a box for recycling. I don't have any cga monitors anymore. I wonder, is the coax output just composite video? Also found a few other fun boards like a hard card, I have given that one to a friend.
 

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Yes, the RCA plug is composite video out and can plug in to a TV, although 80 column text is hardly readable that way.

"Colour graphics"? Hmm, did IBM CGA cards differ for use in other countries?
 
I am not sure if there ever were more than US variants of the IBM CGA board. If you look at the board you recognize that there is no crystal on the board. The PC mainboard has the 14.31818 MHz clock oscilator. It is divded by four to get the 3.58 MHz color subcarrier for NTSC used by the CGA card and also divided by three to get the 4.77MHz CPU clock. Hence the weird clock frequency of the original PC…
 
Funny, I was searching for an Xtal on the board wondering what was used for that. In that case an European TV set would not be able to generate a color picture from that output.
 
Would IBM have bothered to switch the spelling from "color" (American English) to "colour" (British English) on an export version of a product?
 
Maybe IBM made some in Scotland or something? :)

I wouldn’t think they’d do different spellings on something that’s just on the inside. But Tandy had different versions of the coco line with “colour” computers.
 
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