At 2007-05-13T14:22:33+1200, Steve Holdoway wrote:
> up until now, I've been using one of my screens through a kvm switch,
> necessitating its use via analog video. Now, I'm ditching the kvm, and
> have connected both monitors digitally. Here's where the problems are
> starting. The right one just won't sync, and keeps blanking out.
> Monitors are both Viewsonic vg2021m, and the card is a trusty nvidia
> GeForce GE 5200 with 128MB.
Just so I'm sure I understand your problem, you're getting the expected
display on each monitor, but one of them periodically blanks out for a few
seconds and then comes back?
The DVI electronics on that card probably won't be able to drive two DVI
ports at the kind of resolution you're asking for. At a lower resolution
you wouldn't have any trouble.
I've seen similar problems with 5700 Ultras and 6800 Ultras. I had some
luck with using extremely short DVI-D cables and tweaking the refresh rate
down to ~50Hz to get a stable display in one case.
NVIDIA's DVI implementation has been truly awful until pretty recently. The
7xxx and upwards cards are decent, though.
Your choices are: buy a better card, or use VGA for one of the two monitors.
You'll have to experiment to work out which DVI link is the weaker one.
>From memory, it's the 'external' one that is the problem... see below.
> (II) NVIDIA(0): NVIDIA GPU GeForce FX 5200 at PCI:3:0:0 (GPU-0)
> (--) NVIDIA(0): Memory: 131072 kBytes
> (--) NVIDIA(0): VideoBIOS: 04.34.20.16.00
> (II) NVIDIA(0): Detected AGP rate: 8X
> (--) NVIDIA(0): Interlaced video modes are supported on this GPU
> (--) NVIDIA(0): Connected display device(s) on GeForce FX 5200 at PCI:3:0:0:
> (--) NVIDIA(0): ViewSonic VG2021m (DFP-0)
> (--) NVIDIA(0): ViewSonic VG2021m (DFP-1)
> (--) NVIDIA(0): ViewSonic VG2021m (DFP-0): 135.0 MHz maximum pixel clock
> (--) NVIDIA(0): ViewSonic VG2021m (DFP-0): Internal Dual Link TMDS
> (--) NVIDIA(0): ViewSonic VG2021m (DFP-1): 165.0 MHz maximum pixel clock
> (--) NVIDIA(0): ViewSonic VG2021m (DFP-1): External Single Link TMDS
> (II) NVIDIA(0): Assigned Display Devices: DFP-0, DFP-1
> (II) NVIDIA(0): Validated modes:
> (II) NVIDIA(0): "1400x1050,1400x1050"
> (II) NVIDIA(0): Virtual screen size determined to be 2800 x 1050
>
> Has detected the right monitor as being completely different to the left one!
165MHz is the maximum clock frequency for single link DVI. It turns out
that you can drive LCD panels at high resolutions and refresh rates by going
a little out of spec and running in 'reduced blanking' mode, which is
135MHz. Problem is, the older NVIDIA cards can't really drive the link at
165MHz reliably, despite what they advertise (there's probably a class
action waiting there for some keen party).
The card have one internal TMDS and another add-on TMDS part (which is
separate chip, newer ones are usually both internal). This is the internal
vs external TMDS listed in the log output above. Only the internal TMDS
supports the sort of configuration that will allow it to run in the 135MHz
'reduced blanking' mode.
Work out which of the two DVI ports is associated with the external TMDS and
try running the monitor connected to that port via VGA instead.
Cheers,
-mjg
--
Matthew Gregan |/
/| [EMAIL PROTECTED]
