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    SubjectRe: linux as a minicomputer ?
    J. A. Magallon writes:
    > On 2002.04.13 Richard Gooch wrote:
    > >H. Peter Anvin writes:
    > >> Richard Gooch wrote:
    > >> >
    > >> > Actually, there is some impedance matching. I've seen monitors with
    > >> > hi/lo impedance switches. And I've used 15 m long high-quality VGA
    > >> > cables. The result has been pretty good.
    > >> >
    > >>
    > >> The best I've seen is to use Sun D-sub coax or plain coax inputs on
    > >> the monitors that have them. Those are impedance matched and can be
    > >> extended without problem.
    > >
    > >Sure, coax inputs are the best. But there are still problems. Even
    > >expensive coax has higher attenuation at higher frequencies, so the
    > >longer the cable, the more fuzziness you get. Also, there are
    > >differential delay effects between the R, G and B components. You
    > >don't want the pixel components to arrive at different times. So
    > >there's a length limitation there as well.
    > >
    > >But even though coax is better, VGA isn't that bad. 15 m gets you
    > >quite a lot of terminals in a web kiosk (or undergrad computer lab).
    > >
    > >BTW: I agree that X terminals suck. Even worse are SunRays. Ug!
    > >
    > We have built a 'pseudo-CAVE' for presentations, and have six vgas
    > feeding sony projectors with cabling between 15 and 20m, running
    > at 1024x768@32. Quality is ok.
    > The problem is finding good PCI vga cards, even finding any,
    > good or bad. Now they are TNT-M64. I'm also aware that SiS has some,
    > but nothing special. But, to use it as terminals, they could be ok.
    > And coax is not so good. Even with expensive cable, the bounces of
    > the signal made me see double like drunk. Video did not worked right
    > until we got _golden_ connectors and soldered with silver. Believe
    > me you could even put more mony on the cables that on the box.

    Are you sure your monitors had properly matched terminators?


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