AMD Radeon 5770 with three cinema displays

[ScreenSavers]

Hi everyone,

I have a Mac Pro 1,1 (2006 model) that I've had for quite a while. I have been using it for about a year with a flashed "HIS" AMD Radeon 5770 with two Apple Cinema displays, one in each DVI port. The card has two DVI ports, a DisplayPort, and an HDMI port.

I recently got a third Cinema HD display to complete my setup, and an HDMI to DVI and a DisplayPort to HDMI adapter to connect it with. Long story short, neither of them works.

I was advised to get a stock PC 6870 card (knowing that I'll have no boot screen,) but that card doesn't work on any monitors, on any ports.

So I went back to my trusty 5770, where at least I can use two of the ACD's.

Any ideas on how in the world I can get the third one working? What adapters do I need?

Heres my configuration

MacPro 1,1

OS X 10.11.6, El Capitan (Pike's method)
32 GB RAM
250GB Samsung 840 EVO SSD
500GB 7200 RPM HD

 

[ActionableMango]

This problem comes up all the time (can use 2, but not 3 monitors). The two most likely suspects are (1) that you are using three legacy ports or (2) you have an improper flash and one of the ports simply doesn't work.

(1) If you can get any two ports to work right, but never a third, this is probably the problem. AMD 5770 only supports 2 legacy ports. Legacy is everything prior to DisplayPort (HDMI, DVI, VGA). The way around this is to use at least one DisplayPort connection on the card. However, if you use a passive adapter, that still counts as a legacy connection. So if you are doing from DisplayPort to HDMI with a passive adapter, that's still a third legacy connection. If this is the problem, replace the adapter with an active DisplayPort to HDMI adapter.

(2) If there are certain ports that never work, even if it's the only port hooked up, this is probably the problem. Get it flashed right.

 

[ScreenSavers]

This problem comes up all the time (can use 2, but not 3 monitors). The two most likely suspects are (1) that you are using three legacy ports or (2) you have an improper flash and one of the ports simply doesn't work.

(1) If you can get any two ports to work right, but never a third, this is probably the problem. AMD 5770 only supports 2 legacy ports. Legacy is everything prior to DisplayPort (HDMI, DVI, VGA). The way around this is to use at least one DisplayPort connection on the card. However, if you use a passive adapter, that still counts as a legacy connection. So if you are doing from DisplayPort to HDMI with a passive adapter, that's still a third legacy connection. If this is the problem, replace the adapter with an active DisplayPort to HDMI adapter.

(2) If there are certain ports that never work, even if it's the only port hooked up, this is probably the problem. Get it flashed right.

Thank you. I will try that with only two monitors. Thank you for the help!