Matrox Parhelia 128MB

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    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  


Re: Matrox Parhelia 128MB

LAB wrote:
Quoted text here. Click to load it

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).

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.

    "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.)

    "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 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.)

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.


Re: Matrox Parhelia 128MB

    Thank you for your answer. I have set the resolution to 1680x1050: for  
the 22" SyncMaster it's ok.
    The problem is that I can't set a lower resolution for the 15" hp. It  
works best at 1024x768...


Re: Matrox Parhelia 128MB

LAB wrote:
Quoted text here. Click to load it

I don't understand why that would be.

The operation of the two Chrontel chips, should be independent.
So setting a high res on one of them, should not prevent the
other one from being adjusted.

The Matrox GPU chip could have some peculiar behaviors, but
there is no way for me to predict what they might be. Typically,
when something screwy happens to resolution settings, it's a
bug in the driver. As an example, with Intel integrated video
on motherboards, some of the resolution settings are not
available. And that was done, because things like 1650x1080
weren't considered to be "standard" enough. Some driver
writers, insisted on only support VESA resolutions (whatever
those are).

But my experience is, at the hardware level, that hardware is
fully programmable. The width and height, are just down-counters,
and they can be programmed to just about anything.

The PowerStrip software, should also allow programming to any
of those values. As long as the horizontal is divisible by 8
(1680 is Ok), and the vertical is divisible by 2 (1080 is OK),
it should work (that's a typical requirement, but with an
external TMDS like you've got, not even those rules need
to be followed). 1024x768 also passes those rules. When there's
trouble, blame the driver. For example, on my FX5200 card,
the driver writer did some math wrong, and that prevented
a resolution from working. That was fixed in a later driver.


OK, I just had another idea. Remember that there are around
four different modes for multi-monitor. You need to find
out what Matrox uses for terminology, and what subset of those
modes they support.

For example "spanning" is the name of one of the modes.

"Cloning" needs identical resolutions on each monitor.
If the monitors are not the same, they don't support
the same resolutions, then, there will be trouble.
One of the monitors will look ugly (because both are
forced to the same resolution).

Some text explanation here, but no nice pictures.

OK, in this picture, you want "Independent Mode",
*Then*, go back and set the resolution. See if
that helps. This looks like an old control panel
for a Matrox. I used to have a Matrox years ago,
and it had PowerDesk.


Re: Matrox Parhelia 128MB

        About 10 days ago I've solved the problem connecting the 22" monitor  
via DVI, and the 15" via VGA. Only with the two different connections I've  
been able to set the video card to different resolutions.

    Gianluca from Roma, Italy  

Re: Matrox Parhelia 128MB

    >> connecting the 22" monitor via DVI on DVI out #1,
          and the 15" via VGA using an adapter on DVI out #2

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