On Wed, 3 Jul 2002 22:42:12 -0700 (PDT), Neil Bradley <nb@synthcom.com> wrote:
>> > How did I do?
>
>> Give that man a prize! It can load in 64 bits in a minimum of 420ns,
>> and puts it into the Dacs and control system. The loading circuitry is
>> surprsingly simple, and fast; but the board is very stupid-just
>> follows input intructions.
>
>Is this an ISA video card? If so, the bus runs @ 8Mhz, and that's only
>roughly 16 megabytes a second maximum (16 bits at a time). Best case
>that'd take 4 microseconds to load in 64 bits. Or is this PCI?
>
What he's doing is tapping into the video refresh stream. I've never looked
into these video card connectors, but apparently they can be setup so that the
stream of bytes normally sent to the on board DACs, and whatnots, can also be
sent to the connector.
So by attaching some DACs to this connector (with some circuitry that latches
the next byte to the DACs, based on a command byte or something), and then
writing the proper bytes into video memory, the video controller will constantly
refresh the DACs (at like 60hz, or whatever you're video mode is set to.) Once
setup there's no ISA or PCI bus traffic. If a video monitor is connected you
will probably see what appears to be random data, or perhaps repeating data,
depending upon what characters Aaron has chosen as his control bytes.
It's nice in that all the refresh logic is there for you. Unless Aaron has
added some analog logic to drawn lines between endpoints, I think what you end
up with is a digital vector generator, where you are plotting each dot along the
path of the vector.
Aaron, correct me if I'm wrong about any of this.
>> port,MANY old cards that do don't support output (It was expensive
>> finding THAT out) The port is lonely-it needs to be used! I think the
>> connector that runs the new flat-screen monitors may work too,
>
>You mean the DVI connectors? Unfortunately, they're analog, too with some
>additional signalling.
Your probably right about this, I don't think the above technique is going to
work with any of the newer video cards.
-Zonn
---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to vectorlist-owner@synthcom.com.
Received on Wed Jul 3 22:57:33 2002
This archive was generated by hypermail 2.1.8 : Fri Aug 01 2003 - 00:34:04 EDT