MP 1,1-5,1 Mac Pro 2010 not seeing boot screen

[VivienM]

So... I bought a 2010 Mac Pro today. As far as I can tell, someone ordered a crazy souped up configuration from Apple - 2x2.93GHz Xeons, 512GB SSD, 64GB of RAM, 2x5770s, etc and never upgraded the machine or otherwise changed it until I come along and buy it 10 or 12 years later.

But... I cannot get the boot screens to display. No option menu boot selector, no Apple logo, monitor just dead until mid-way through the macOS boot process, etc. In other words, what you would expect if I put a non-UEFI/Mac friendly card in there, but these are clearly Apple 5770s with the 2x mDP and the DVI connectors.

Tried it with two monitors. Same results.

Any thoughts? Should be using one of the two 5770s and not the other (I think I tried both)? What resolution/display mode does the boot stuff require on the Intel Macs? (I know from experience with my MDD that the PPCs, at least, boot up in a slightly unusual display mode too that many newer monitors don't support)

 

[tsialex]

Some AppleOEM GPUs, specially the HD 5770 and HD 5870 do not provide pre-boot configuration support if your display is DP1.2 or newer, so, probably almost all modern displays that do not have a DP1.1 fallback mode won't have pre-boot configuration support and will only work after macOS loads the GPU drivers.

See if your display have a DP1.1 setting or try with DVI.

 

[VivienM]

Some AppleOEM GPUs, specially the HD 5770 and HD 5870 do not provide pre-boot configuration support if your display is DP1.2 or newer, so, probably almost all modern displays that do not have a DP1.1 fallback mode won't have pre-boot configuration support and will only work after macOS loads the GPU drivers.

See if your display have a DP1.1 setting or try with DVI.

The Lenovo 27" monitor I was using just now has a setting for DP 1.2 vs DP 1.1. Set it to DP 1.1, now it works...

Grrrrrreat. The fun of vintage machines... (although, can we really call this thing a vintage machine?)