I agree,
having digital + std. analog + hi-speed analog is not a good
combination. If I had to develop a graphic board from scratch (targeted
for FOSS) and had known the information presented on the mailing list
last week (about demands), the outputs would be:
head1: Dual link DVI-D
(hi-res LCD testing)
head2: DVI-I with:
Color precision analog (12-16bit/channel)
(color calibration, up to 1600/1200 @ 100 = ~200MSPS)
Single link DVI
(playing with dualhead, having ordinary LCD panels)
4 channel LVDS (using pins of the second DVI link)
(for cheap direct tft-lcd attachment)
head3: SVHS / component video
(low speed 10bit DAC for SD television quality)
+GPIO (one can construct head4 as digital RGB)
(I'd like to have one of all interfaces - because the purpose is to TEST
them, NOT USE them and I do not see much interest in the hispeed analog).
On the other side, when the high-speed analog will be needed, then
constructing a box which accepts dual link DVI and contains fast DAC
would be OK even if the price will be higher (remember - one who need
such a signal will have a relatively expensive monitor). Creating this
external dac-box when having some know-how from the OGD project should
be trivial.
Daniel
James Richard Tyrer wrote:
> I can't help but think that with the design issues piling up, that we
> should rethink the second video head.
>
> Pin budget problem for the FPGA.
>
> Unresolved connector issues.
>
> Cost issues.
>
> Cable impedance issues.
>
> Market demand questions.
>
> So, it appears to me that we should not offer the 500 MSPS head on the
> first board. We would be better to just offer two 330 MSPS heads with
> DVI connectors and the TV output. This would mean that we would have
> sufficient pins to offer 10 bits per color for both heads. We know that
> there is a market for this feature.
>
> I also wonder if these 50 ohm high resolution monitors are currently
> being sold and if there are many people using them.
>
> OTOH, it appears that there would be a demand for 10 bit per color
> RAMDAC for color correction.
>
> If we determine that there is a sufficient market for 500 MSPS video,
> then we could offer it on the production board as a second board (or an
> external box) connected by LVDS over a cable. If we are committed to
> using the LVDS transmitters, there is no need to have the 500 MSPS video
> to develop the FPGA and software.
>
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