As you can see from the attached pictures monitor n2 is stuck at 640x580
What are the resolutions of all other monitors, and how are they all connected?
the monitors are Samsung syncmaster 204b their max resolution is 1600x1200 and they are all connected to one video card the ati hd5870 eyefinity six edition (six monitors) they are all ok except n.2 which has a resolution of 640x580 and can't be changed.
I meant specifically the type of connection, as in native (or active adapter) DisplayPort versus passive DisplayPort to DVI/HDMI/VGA.
Though now that I've done the math, I think I may already know the answer. I think you have two monitors hooked up via passive adapters, and three via DisplayPort (either native or via an active adapter).
The 5870 came out before DisplayPort 1.2, which means it's using DisplayPort 1.0 or 1.1, which has a maximum usable throughput of 8.64Gbps. A single 1600x1200 display with 24-bit color and a 60Hz refresh rate requires 1600*1200*24*60/2**30 = 2.575Gbps of throughput. Three of them add up to 7.725Gbps, leaving just 0.9Gbps or so available. You should be able to get 800x600x24@60Hz out of that, but if I'm assuming the wrong transfer mode, usable throughput goes down a bit, which could leave you with only enough for that 640x480 resolution on the sixth monitor.
The upshot is, I'm reasonably sure your card simply cannot output to six 1600x1200 displays. You'd need a lower resolution for six displays. Or, you can get a new card which supports DisplayPort 1.2 and has double the available throughput. You'd also need a MST hub to connect all six monitors.
WOW thanks for doing some fancy calculations for me but I have this set up since 2010 and it always worked well until I got a virus and I reinstalled window 7 and when I reinstalled the driver the 640x580 problem started although another monitor was going on and off form time to time so I am now using 4 monitor out of the six.
I use six miniport to dvi-d active to connect the monitors to the card.
After doing some test I think I have to change the the miniport .
Thanks for all you help
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