MSDOS Source code leaked
caveguy at sbcglobal.net
Fri Oct 13 19:59:37 CDT 2006
Control Systems made an Artist 2 card which was ega like and supported genlock in both NTSC or PAL
but not both there was a coil and a cap that had to be changed.
It was sold/used for the video overlay of title info on live video.
There was a video titleing system that used it, I forget its name.
I did an Autocad driver for it in about 1985 or 86ish to do video traceing.
Still have a few somewhere in the basement.
The other Bob
On Fri, 13 Oct 2006 22:45:09 +0100 (BST), Tony Duell wrote:
>> On Fri, 13 Oct 2006 13:43:42 +0000, Jules Richardson wrote:
>> >That's interesting, though. IBM must have believed that the 5150 would be a
>> >global product and I'd expect that was the plan all along - so why put
>> >circuitry on there for one market only?
>> I do not think there was ever was a PAL version of the CGA card.
>There wasn't. In fact I've never seen a PAL version of any classic
>IBM-compatible video card.
>It was possible to reprogram the 6845 registers on a CGA card to give
>European TV timing, albeit still with NTSC-like colour output on the
>composite connector. I have -- somewhere -- a box that plugs into the DE9
>(TTL RGV output) connector on a CGA card and which encodes said signals
>to PAL. The result (after repogramming the 6845) is a PC that can display
>on a European TV set.
>> As far as I know the CGA card was the only one dependant on the base clock freq being right on.
>A few other cards use the OSC signal from the ISA connector, but AFAIK
>none of them depend on the exact frequency like the CGA card does.
>> or It would loose color burst. I always thought the 4.77mhz was chosen because it could also be used as the
>> clock ref for the video.
>Absolutely. The mater clock is 14,xx MHz. That was chosen becasue it's 4
>tiomes the NTSC subcarrier and the division by 4 gives the quadrature
>signals needed to make a simple NTSC encoder. The CPU clock is the same
>master clock divided by 3 (I have no idea why the Intel clock generator
>has a /3 stage in it...)
More information about the cctalk