LAB said:
Hi all
On this computer I have a Matrox Parhelia 128MB with 2 DVI outs. The
monitor was a hp 1530. Now for my work I need a bigger screen, then I've
added a Samsung SyncMaster 226BW. It has a resolution 1680x1050, then
I've set the card to that resolution.
The problem is: can I set DVI 1 out to 1680x1050 and DVI 2 out to
1024x768? I haven't been able to do that. 1680x1050 in the hp 1530 is
poorly readable...
Thanks!
Gianluca
If it is poorly readable, that means the output resolution is
not 1680x1050. It's some other value.
Your board has two Chrontel DVI transmitters on it. Sometimes
those are used, if the DVI transmitters are not inside the GPU
chip itself. A slower parallel bus comes out of the GPU, and
the Chrontel does gear grinding, to send out TMDS encoded data
at up to 1650 Mbits/sec (= 165MHz pixel clock).
http://upload.wikimedia.org/wikipedia/commons/5/52/Matrox_parhelia_128mb_agp.jpg
I couldn't tell for sure what the part number was on the Chrontel,
and it could be CH7301. This is the datasheet. The only thing that
counts right now, is a single sentence in there.
http://www.chrontel.com/media/Datasheets/7301ds.pdf
"Any values of pixels/line, lines/frame and clock rate are
acceptable, as long as the pixel rate remains below 165MHz"
That means the Cnrontel is not the limiting factor. And the
existence of the Chrontel, means the GPU shouldn't have a problem
either. The Chrontel absolves the GPU from making nice looking
DVI signals. (Only Chrontel has to make it work, not Matrox.)
It means the GPU can be "pure digital".
On the Wikipedia DVI article, you can see that 165MHz pixel rate,
supports up to 1920x1200 with reduced blanking timing format.
So 1680x1050 should have been easy to do. Even 1600x1200 can
be done with GTF. (Blanking is needed mostly by CRTs, while
LCD monitors need hardly any at all. That's why we can reduce it,
because the LCD doesn't care about blanking like a CRT would.
On a CRT, blanking covers the period during which the beam
flies back to the left.)
http://en.wikipedia.org/wiki/Dvi
"Example display modes (single link):
WUXGA (1,920 × 1,200) @ 60 Hz with CVT-RB blanking (154 MHz)"
The Matrox folks at times, have done some odd-ball things.
Like failing to make VESA modes work properly at BIOS level,
on a couple of their cards. But I would not have
expected a problem on a modern card, getting 1680x1050 and
1024x768 on the outputs, in dual head mode.
The Chrontel also has three DACs inside, implying it also does
VGA outputs. Occasionally, a high resolution setting on VGA,
doesn't look so nice on an LCD. If you have one of the older
LCD screens like I do, all it's got is VGA, and you have to be
satisfied with the results. But your new SyncMaster should
have DVI-D on it, and there's no excuse for that to not work.
At high resolution, the digital (DVI-D) can look better than
the analog (VGA). At low res, they look about the same.
And all that leaves, is the resolution being sent by the
video card, not actually being the 1680x1050 it claims to be.
The fuzziness comes from scaling on the LCD panel.
*******
The only thing I can suggest, is download PowerStrip from
entechtaiwan.com and use the evaluation period for the
software, to try programming the resolution on your card.
It's used for setting custom resolutions. Perhaps you will
get some feedback from that program, if the software is
fudging the settings. (You can also play with mode lines
in Linux, if you're curious. Linux would give you much
the same capabilities, for testing the monitor.)
http://www.entechtaiwan.com/util/ps.shtm
Entechtaiwan also has a forum, and the software programmer
there has written a few FAQ entries regarding how well the
various chips are supported and so on.
Matrox used to have a user forum as well (chock full of hack
info for Matrox cards), but one day they wiped it, and I
haven't been back there since. It's one of the reasons
I wouldn't participate in a web forum, knowing the whole
forum can be wiped on a whim.
Paul
