Should 5770 show boot screens on MDP?

[Botts85]

Hello,

I have a 2010 Mac Pro with the stock ATI Radeon 5770.

When I boot with a 20" DVI Cinema Display attached, everything works perfectly , I get drive selection if I boot holding option, and I can see the password field to disable FileVault 2.

Where my issue arises is that my normal setup is two Dell U2715H displays plugged in through Mini DisplayPort (not using MST). Even just connecting one U2715H alone via Mini DisplayPort causes the Mac to display no video until midway through the boot into an macOS partition.

Is the lack of EFI display an expected behaviour of the 5770 when connected to a MDP display? Or is there a way I can cause the Mac Pro to display video whilst booting with a 5770 and MDP display(s).

Thanks!

 

[Fl0r!an]

The mDP should display a boot screen like the other ports. However, there seem to be some displays which the Mac EFIs "don't like". Personally I have a similar Dell U2515H, which won't display a boot screen on any Nvidia GPU, only my R9 280 seems to be able to display it, but only through one connector (not sure if it's HDMI or DP).

That said, I know that a friend of mine is sucessfully driving his Dell U2715H with a flashed HD 5770 through DP, including boot screens.

 

[Botts85]

The mDP should display a boot screen like the other ports. However, there seem to be some displays which the Mac EFIs "don't like". Personally I have a similar Dell U2515H, which won't display a boot screen on any Nvidia GPU, only my R9 280 seems to be able to display it, but only through one connector (not sure if it's HDMI or DP).

That said, I know that a friend of mine is sucessfully driving his Dell U2715H with a flashed HD 5770 through DP, including boot screens.

Troubleshooting that might be a pain if it's monitor specific. Flashing an OEM Apple 5770 is a step I wasn't hoping to have to take.

I'm going to try and track down a R9 280x now and flash that.

 

[Botts85]

The mDP should display a boot screen like the other ports. However, there seem to be some displays which the Mac EFIs "don't like". Personally I have a similar Dell U2515H, which won't display a boot screen on any Nvidia GPU, only my R9 280 seems to be able to display it, but only through one connector (not sure if it's HDMI or DP).

That said, I know that a friend of mine is sucessfully driving his Dell U2715H with a flashed HD 5770 through DP, including boot screens.

Thanks. I got the boot screens through HDMI with a flashed R9 280x, but as soon as I plug in a second U2715H through Mini-DisplayPort it loses all boot screens.

Have you managed to get boot screens with multiple Dell displays?

I'm going to try HDMI+(DVI-HDMI) cable and see if that will work.

 

[Fl0r!an]

So you're talking about two U2715H's? I only have one U2515H, so I can't replicate that.