quack surgery on a VGA card

[Uwe Doering]

chip at chinacat.Unicom.COM (Chip Rosenthal) writes:

>I am running ODT on a Micronics 386/20 with an Orchid Prodesigner running
>in normal 640x480 VGA mode.  This board brings a trace out to the IRQ9/IRQ2
>bus pin.  I am assuming it's the vertical retrace signal.  I further
>believe that such a signal isn't used by the system, therefore I took an
>Xacto knife to it to free up that IRQ.
>
>Now I am seeing flaky behaviour on the ODT machine.  Every once in a
>while, the display gets scrambled.  Things continue running, but it looks
> [stuff deleted]
>Can anybody say definitively
>whether I made a major goof?  I will try reconnecting that trace tonight
>to see if there is any effect.

I assume you mean the B4 bus contact. I've done the same thing on several
VGA cards with no problems at all. UNIX doesn't use this IRQ. And the
VGA BIOS in the EPROM on the card isn't used under UNIX (with the exception
of VP/ix). Therefor it really doesn't matter whether this trace leads to
the bus connector or not. Currently I'm running an AST 4-port compatible
serial card on IRQ2/9 and I use an Optima/1024 VGA card which is compatible
to the Orchid Prodesigner card. This is with ISC 386/ix 2.0.2.

     Uwe
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