Resolution Problem with Four Monitors on Mac Pro 3,1

Question

Resolution Problem with Four Monitors on Mac Pro 3,1

Hi,

I'm running 10.10.3 on a Mac Pro 3,1 (early 2008). This has 2 NVIDIA GeForce 8800 GT card installed in it with two monitors attached to each (4 in total).

I originally had 3 monitors each running at 1920 x 1200 @ 60 Hertz (NTSC), this worked fine. Today however I added a 4th monitor. The 3 original monitors are all Samsung 24A450's, the new one is an updated version of the same monitor - Samsung 24C450. When the monitor arrived, I shut down the Mac Pro, then attached the monitor and powered up again. When it started up, only two monitors were showing. After trying a couple of things, I shut down and disconnected the new monitor and powered up again, all 3 of the originals came back up. I then tried connecting the 4th Monitor (the 24C450) while the machine was still running and low and behold it recognised it! I configured it and it seems to work ok.

I have one remaining problem with it, the 3 original Monitors have resolutions of 1920 x 1200, but the newer monitor won't go above 1920 x 1080. Why is this? Is it possible to get this new monitor to match the 1920 x 1200 resolutions? If I got an active adaptor would this make it use the higher resolution. I'm connected via DVI on all four, is it a cabling issue? I am using the cable that came with the 4th monitor, but have another one on order which I'll try when it arrives.

All the Best

Dave

Mac Pro, OS X Yosemite (10.10.3)

Posted on Apr 28, 2015 6:55 AM

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Answer 1

lllaass

Level 10

210,411 points

Apr 28, 2015 7:37 AM in response to LookToWindward

What port on the graphics card are you using?

For resolution greater than 1080p using a mini displayport card output and a DVI monitor input requires a dual-link adopter like

http://store.apple.com/us/product/MB571Z/A/mini-displayport-to-dual-link-dvi-ada pter

If the monitor has a displayport or mini displayport input that will will with just the appropriate cable MDP>MDP or MDP>DP or DP>DP)

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Answer 2

Apr 28, 2015 8:02 AM in response to lllaass

There are 2 NVIDIA GeForce 8800 GT cards installed with 2 monitors attached to each (4 in total) - there are two DVI ports on each card, so I'm using DVI cables between the 4 ports on the 2 cards connected to 4 monitors, DVI both ends.

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Answer 3

lllaass

Level 10

210,411 points

Apr 28, 2015 8:24 AM in response to LookToWindward

Designed by NVIDIA – For Mac

The NVIDIA® GeForce® 8800 GT for Mac is designed to tackle everything your gaming, graphic-designing, art-directing, illustrating, web-browsing, photographing, video-producing, HD-video-watching self can throw at it. With 112 processing cores and two DVI ports capable of driving two 30-inch displays at full resolution (2560 x 1600), the only thing to worry about is desk space. - See more at: http://www.nvidia.com/object/product_geforce_8800gt_for_mac_us.html#sthash.YGCkc qJJ.dpuf

When you go to Display Preferences for the new monitor what resolutions are available if you select the Scaled option?

You can also try one of these apps

SwitchResX – The Most Versatile Tool For Controlling Screen Resolutions On Your Mac

Display Menu from Mac App Store

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Answer 4

Apr 28, 2015 8:56 AM in response to lllaass

On the New Monitor (24C450), which is Rotated 90 degrees - Portrait Mode:

1080 x 1920 (this is the one selected)

900 x 1600

756 x 1344

720 x 1280

On one of the older monitors (24A450), which is also Rotated 90 degrees - Portrait Mode:

1200 x 1920 (this one is selected)

1000 x 1600

840 x 1344

800 x 1280

640 x 1024

On the other two 24A450's:

1920 x 1200 (this one is selected)

1600 x 1000

1344 x 840

1280 x 800

1024 x 640

Thanks for helping, all the Best

Dave

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Answer 5

lllaass

Level 10

210,411 points

Apr 28, 2015 9:01 AM in response to LookToWindward

What if you use landscape mode for the new monitor what is available? Using portrait mode may be the problem.

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Answer 6

Apr 28, 2015 9:19 AM in response to lllaass

If I set the rotation to standard:

1600 x 900

1344 x 756

1080p

720p

(never seen the last two before!), I saw your note on SwitchResX and downloaded it and tried it, I might be doing something wrong, but I tried setting it to 1920 x 1200, it said "not installed - reboot needed", after restart, the status is "Not activated - invalid?"

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Answer 7

lllaass

Level 10

210,411 points

Apr 28, 2015 9:32 AM in response to LookToWindward

Try Display Menu from the mac App Store, the free version.

If could be that the Mac does not understand the identifying code sent out by the monitor.

I would try resetting the SMC and NVRAM/PRAM

Intel-based Macs: Resetting the System Management Controller (SMC)

About NVRAM and PRAM

And then first try with only the new monitor connected

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Answer 8

Apr 28, 2015 9:34 AM in response to lllaass

I tried Display Menu, still can't get the same resolution, I'll try resetting NVRAM/PRAM and disconnecting the other monitors if that doesn't work and report back.

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Answer 9

Apr 28, 2015 10:17 AM in response to lllaass

Hi Again,

I tried resetting the SMC and NVRAM/PRAM, still does't work. I then tried disconnecting all but the new monitor, still can't get 1920 x 1200 and it doesn't seem to work using SwitchResX or Display Menu.

Could it be to do with the cable I am using? As I said earlier it's the one that came with the monitor, I have another one on order and will try it when it arrives.

Thanks for your help on this.

All the Best

Dave

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Answer 10

lllaass

Level 10

210,411 points

Apr 28, 2015 10:18 AM in response to LookToWindward

The cable came with the new monitor right?

Try deleting the system preference plist

Deleting the System Preference or other .plist file

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Answer 11

Apr 28, 2015 10:36 AM in response to lllaass

Yes, the cable came with the monitor, there were two cables, a DSUB and a DVI, I'm using the DVI, I think I have an DSUB to DVI Adaptor somewhere, if I do, do you think it's with trying it? I'd swap the cables on one of the other 3, but it's hard to get the cables out at both ends.

I deleted the system preference .plist file, still can't get the 1920 x 1200 resolution.

Cheers

Dave

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Answer 12

lllaass

Level 10

210,411 points

Apr 28, 2015 10:46 AM in response to LookToWindward

You can try the DSUB.

I think the problem is the the Mac just does not identify the monitor properly

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Answer 13

Apr 28, 2015 10:56 AM in response to lllaass

Ok, well that's a start anyway. I did a google on DVI earlier and there are different types of cables (with more or less pins), I'm wondering if they sent a cheap cable with the monitor and it doesn't have the right number of pins for this resolution. I'll try the DSUB if I can find the adaptor, otherwise I'll have to wait until Thursday when the new cable arrives. You've been great trying to help like this and I will definitely followup on this and hopefully a solution will appear.

All the Very Best

Dave

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Answer 14

lllaass

Level 10

210,411 points

Apr 28, 2015 11:13 AM in response to LookToWindward

I do not think so. There are two types of DVI cable/connections. SIngle-link that is good for 1920x1200 and dual-link up to and including 2560x1600. The dual-link has more pins.conductors

http://en.wikipedia.org/wiki/Digital_Visual_Interface

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Answer 15

Apr 28, 2015 11:45 AM in response to lllaass

Thanks for this, I did some googling for the monitor and found this:

http://www.samsung.com/ie/consumer/pc-peripherals/monitors/professional/LS24C45K BWV/EN

So it should work, I think you are probably right, Yosemite is mis-identifiing this monitor, but how to fix? I would have thought that SwitchResX would have gotten around it, but it seems not.

I guess that Apple won't be very responsive on this as it's an odd ball configuration as far as they are concerned.

All the Best

Dave

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