[comp.sys.ibm.pc.misc] IBM CGA composite output

steve@clmqt.marquette.MI.US (Steve Lasich) (04/26/91)

gla@cbnewsj.cb.att.com (gregory.l.allen) writes:

>My father has an AT&T 6300.  He has disabled the indigenous video card and has
>used other CGA video cards successfully.  I recently acquired a true Blue
>original IBM CGA card (full-card) because it is the only source of <<color>>
>composite output

>1) is there anything else that needs to be done to use an IBM CGA card in a
>        6300 (do we need a bus corrector, etc.?)

I believe the problem described is unrelated to the use of an AT&T 6300.
This is a red-herring.  Until last year our university computer lab
contained 65 "True Blue" IBM PCs (PC and XT boxes) with "True Blue"
IBM CGA full-length cards.  Every video card in the lab exhibited
the same behavior.  The composite signal renders color as various
monochromatic hatch-mark patterns.  When colorburst is enabled this
renders 80 column text totally unreadable.

I haven't got any good advice about this problem but I can assure you
that you are not alone and you are not having an AT&T compatibility
problem.

Steve Lasich                         Bang: ..!mailrus!sharkey!clmqt!steve
Microcomputer Lab Coordinator        Domain: steve@clmqt.marquette.mi.us
Northern Michigan University         Safest: acsl@nmumus.bitnet

drudman@hpcc01.HP.COM (Drew Rudman) (04/30/91)

As far as I know, the composite port on ANY CGA card supplies only a black and
white signal (it samples off of the intensity signal of the CGA.)  No CGA card
I know of (and I used to sell all kinds - new and used) will provide you with
a color composite signal.

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