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2010 Mac Pro with 5870 - 3 monitors not working

I just got a new 2010 2.4GHz 8-core Mac Pro with a 5870. The tech specs say that I can drive 3 monitors with that card, however it's only letting me drive two. I have two Mini DisplayPort-to-DVI adapters connected to two Samsung P2770HD monitors at 1920x1080 resolution and the DVI port connected to a Samsung T260 at 1920x1200. I'm using DVI-D cables on everything.

When I connect all three monitors, the two monitors connected to the Mini DisplayPorts are detected, but the monitor connected to the DVI port isn't. If I unplug one of the DisplayPort monitors, the DVI monitor is detected and works fine.

The only note on the tech specs page says:
"2. Connecting more than three displays requires installation of two ATI Radeon HD 5770 graphics cards."

Hitting "Detect Displays" on the Displays System Preferences page doesn't detect the 3rd monitor. I've tried rebooting, sleeping, disconnecting, etc - no luck.

Any suggestions? Thanks,
-Bryan

2010 Mac Pro, 8-core, 2.4 GHz, 8GB, 5870, Mac OS X (10.6.4), 3 monitors

Posted on Aug 24, 2010 9:38 PM

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59 replies

Aug 24, 2010 10:36 PM in response to Bryan Duke

I just spent an hour digging around & found this: http://support.apple.com/kb/HT4279

According to that page, to get three DVI monitors to work, you have to use the Mini DisplayPort to Dual-Link DVI Adapter on each Mini DisplayPort if you want three monitors. The page says that if you want to use two DVI displays, you can use the Mini DisplayPort to DVI Adapter.

So...if this is true, I have to buy two $99 adapters to use 3 DVI monitors? It would have been cheaper to get two 5770s instead of the 5870. It baffles me that the $29 Mini DisplayPort to DVI Adapters that I'm using (MB570Z/A) don't work for this.

I really hope this isn't the case. If so, this caveat really needs to be on the tech specs page. $200 extra for monitor connections on a $4000 computer is ridiculous.

Can anyone clarify/verify this? Thanks,

-Bryan
http://acceleroto.com

Aug 25, 2010 8:27 AM in response to Bryan Duke

This may be IS a complete Red Herring, but these are discussions, right?

The display you have connected to the DVI port certainly seems to have a lot of optional ways to connect, in addition to full-digital. I wonder whether it is picking up the VGA signals (the bar and the four pins around it at the end of the connector) for some reason, and that may be influencing how many can be used at once.

Edit: Nevermind my goofy theory, the article says this has nothing to do with it. The article you cited seems pretty unequivocal. When the specs were first issued, it said "max of two DVI displays", then was amended to remove that footnote. I guess they need half that footnote restored. But it certainly does stink to be the guy on the "bleeding edge".

Message was edited by: Grant Bennet-Alder

Aug 25, 2010 11:09 AM in response to Bryan Duke

There are 2 clock generators capable of running a DVI display in a 5xxx cards from ATI.

To run 3 @ DVI displays, you will need to add a SINGLE MDP to Dual Link adapter. You can also refer to this as an "Active" adapter, it creates it's own clock and you will be able to run 3 DVI's.

I realize that you don't have DUal Link size displays, but trust me, this is what you need.

You can spend hours and days running in circles chasing other ideas, or buy an active adapter and run 3 displays today. Your call.

Aug 26, 2010 5:17 PM in response to Bryan Duke

Bryan,

I'm going through the exact same thing. Thanks for the pointer to the support page -- I hadn't seen it before. Another discussion forum suggested the same thing as DPArt, that we would need only ONE dual-link adapter. My dual-link adapter just arrived and no dice: only two monitors at a time work. Same as before.

So, I think the support page must be right: for some reason, we really do seem to need TWO dual-link adapters. At least that better be the case. I'd hate to buy yet another adapter and not have it work.

It sure sounded good at the time, though: "Dual-display and triple-display modes...Simply attach multiple monitors and Mac OS X will recognize all the displays." Sigh.

Aug 26, 2010 5:45 PM in response to homagetogorto

Yup sigh is right.

I just got home from buying ONE Mini DisplayPort to Dual-Link DVI Adapter. The Mac Pro with 5870 will still only drive 2 monitors. Spending $200 extra to get all my monitors to work is really pathetic - two adapters cost as much as an entire video card.

I'm curious about driving one of the monitors with VGA. My Sansung T260 seems to do quite well with VGA. The 2 DVI monitors + 1 VGA monitor setup isn't listed on the support page.

Can anyone from Apple chime in on this?

Thanks,
-Bryan

Aug 27, 2010 4:08 AM in response to Bryan Duke

I've got a MacPro 2010 with ATI 5770 and the same problem with two Samsung SyncMaster 245T and an old Acer AL1731.
I tried many different configurations, all three monitors have DVI and VGA inputs (SyncMaster 245T also HDMI).
It works with two monitors connected with two Mini DisplayPort-to-VGA and the third monitor connected directly on DVI (at the highest resolution of each).
Two DVI and a VGA does not work.

I hope to be helpful
-Pierluigi

Aug 27, 2010 12:26 PM in response to Bryan Duke

Can anyone from Apple chime in on this?


Not from here. This is the still User-to-User discussions \[soon to be Apple support Communities, with whatever changes that will bring]. At this writing, Official Apple representatives do not often visit here.

For an official answer from Apple, contact your authorized Apple Reseller or telephone Applecare (covered FREE for 90 days -- even if you did not buy the extended coverage). They do everything by Serial Number, so have your Computer serial number handy.

Aug 28, 2010 2:17 PM in response to Grant Bennet-Alder

I just got off the phone after an hour discussion with AppleCare. I talked to two levels of support techs & they said two Mini DisplayPort to Dual-Link DVI adapters are indeed required to get three DVI monitors to work - at $99 each.

I also tried connecting a single DVI-to-VGA adapter with two Mini DisplayPort to DVI adapters and that still only gave me two working monitors.

It still seems odd that it requires TWO of the $99 adapters to work. If you look at ATI's 5870 specs ( http://www.amd.com/us/products/desktop/graphics/ati-radeon-hd-5000/hd-5870/Pages /ati-radeon-hd-5870-specifications.aspx ), it looks like the standard 5870 config only requires one DisplayPort display if you want to use three displays. I asked AppleCare about this difference between their cards & the ATI spec & they didn't have an answer why there was a difference. Maybe I'm misinterpreting the spec.

I asked them to put in a request to change their Mac Pro Tech Specs page to reflect the additional parts required to get three monitors working correctly. If I had known that I needed to buy $200 worth of connectors, I would have bought two 5770s instead of one 5870.

On a related note, I asked about adding another graphics card to my Mac Pro. AppleCare told me that because the 5870 uses two power adapters, you can't add another 5770 or 5870 to the Pro. They said a 2010 Mac Pro with a 5870 "is maxed out."

I may try to find a SATA power plug to PCIe power adapter and drop in an 8800GT I have. I'm not sure if it'll work though - the 5870 takes up a lot of room & there might not be room to get another card in the other 16x PCIe slot.

A friend suggested I try MonoPrice's Mini DisplayPort to Dual-Link DVI adapters. They're $65 each:
http://www.monoprice.com/products/product.asp?cid=104&cp_id=10428&cs_id=1042802&pid=6904&seq=1&format=2 If the 8800GT doesn't work, I'll try to the MonoPrice adapters.

For now, I guess I'll be happy with two of my three monitors working.
-Bryan

Aug 28, 2010 2:29 PM in response to Bryan Duke

A friend suggested I try MonoPrice's Mini DisplayPort to Dual-Link DVI adapters. They're $65 each:

Note that the MonoPrice adapter doesn't seem to have the USB socket that is present on the Apple adapter, so if used with displays that need USB (such as Apple displays), you will use two USB connectors on the computer for each display.

2010 Mac Pro with 5870 - 3 monitors not working

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