MP 1,1-5,1 5,1 GT120 & HD5770: No video output via DP to Ultrawide Display

[theMotoMan]

Hey gang, I recently acquired a 2012 5,1 that came with no drives and RAM. Got it home and tried to get it booted using the HD5770 connected to my LG 35" Ultrawide via the mini DP on the card to the DP on the display. No output whatsoever. Basically no signal detected by the display as it immediately wants to sleep. Tried a 34" Gigabyte ultra wide via DP and got the same results. Bought a GT120 off of eBay and it reacts the same way. Tried a DVI to DP cable and no joy. I borrowed an old Dell DVI capable display and that works just fine.

It definitely is a problem with the old cards connected to a newer display, but I don't get it. I would at least thought I would get a lower resolution output (not the native 3440x1440), but I get absolutely no output. I have a mini DP to HDMI cable arriving from Amazon today and I will give that a go, but am wondering what the deal is.

I also set my LG to output DP 1.2 instead of 1.4 and that had no effect.

I also realize that I need a newer GPU and I will be buying one, but I ought to be able to do the preliminary setup on the stock GPU. I intend to run Open Core on it, but when things go south, I want to be able to insert the stock GPU with a boot screen and connect it to my LG display and troubleshoot the problem.

 

[MarkC426]

What Mac OS version is installed....?

 

[theMotoMan]

What Mac OS version is installed....?

Well, I currently have High Sierra, but it gives no video output during the boot process. There is no boot menu, no diagnostics, etc. A Mac should be able to enter diagnostics, the boot menu, or at least show the question mark without booting into an OS. As mentioned above, I get all the normal output when connected to an old DVI display. I get the boot menu, the question mark when there is no drive installed, etc.

 

[MarkC426]

I don't think you can run a Mac Pro without a startup disk (or external system disk/Mac OS installer).

 

[theMotoMan]

I don't think you can run a Mac Pro without a startup disk (or external system disk/Mac OS installer).

It will boot to the "question mark" screen if you have a stock GPU in it. When I connected it to a DVI display it actually did this. The real question is why won't it work with a newer display.

 

[tsialex]

AppleOEM GPUs only have pre-boot configuration support with DP1.1 displays (and older types).

 

[MarkC426]

The real question is why won't it work with a newer display.

Possibly because it is 'a newer display' which didn't exist when your Mac was made, and your Mac doesn't recognise it..

 

[theMotoMan]

AppleOEM GPUs only have pre-boot configuration support with DP1.1 displays (and older types).

Okay, that makes sense! Thanks!

Any chance the DP->HDMI adapter will work? I guess I will find out in a couple of hours when the cable is delivered.

 

[theMotoMan]

So the DVI -> HDMI cable does work and show the boot menu, etc., but is limited in the resolution. 3440x1440 looks like crap and 1080p looks good but is stretched of course. I think I am going to send this one back and try a mini DP to HDMI and see if that works better. @tsialex: thoughts?

 

[Borowski]

All Apple OEM-cards have limited resolution in pre-boot, keep in mind the age of the cards.
The driver (inside EFI) isn't able to provide any output for 4K or UWQHD, thats why limiting to DP1.1 (lower bandwidht) resulting in output, but depending on display with lower resolution and (or) refreshing rate.

Best solution: Grab a modern card and GOPEnabler for bootscreen support.

 

[MarkC426]

So the DVI -> HDMI cable does work and show the boot menu, etc., but is limited in the resolution. 3440x1440 looks like crap and 1080p looks good but is stretched of course. I think I am going to send this one back and try a mini DP to HDMI and see if that works better. @tsialex: thoughts?

A different cable won't change what you get from your OLD gpu to your modern monitor.
As suggested above get a newer gpu.

 

[tsialex]

AppleOEM GPUs for MacPro4,1/5,1 have a DP1.1/TDS bandwidth that can work up to 2560x1600/HBR. This is a physical limitation and you can't do anything about that besides replacing with a modern GPU.

If the display have a default resolution over that, it will work in compatibility mode/low resolution.

 

[theMotoMan]

@MarkC426, @tsialex

I did some more experimenting and the HD5770 is more capable than we first thought. When I have the old DVI display connected and the 35" Ultrawide, it boots fine and drives both displays at max resolution. Here is a screenshot of it. I have ordered a Mini DP->HDMI cable and I will see if there is any difference with that cable. These screenshots were taken with Dell connected DVI->DVI and the LG connected Mini DP->DP.

BTW, I stated I'm getting a new GPU, just need a setup that works in an emergency when things go south and I need a boot screen.

 

[tsialex]

@MarkC426, @tsialex

I did some more experimenting and the HD5770 is more capable than we first thought. When I have the old DVI display connected and the 35" Ultrawide, it boots fine and drives both displays at max resolution. Here is a screenshot of it. I have ordered a Mini DP->HDMI cable and I will see if there is any difference with that cable. These screenshots were taken with Dell connected DVI->DVI and the LG connected Mini DP->DP.

No it's not. It's a DP1.1 GPU that is extremely limited with anything over 2560x1600, the greatest resolution that still have an acceptable refresh rate.

WQHD@30Hz have almost the same bandwidth requirements of 2560x1600@60Hz, but 30Hz is not enough for most people. If works acceptably for your workflow, good enough.

BTW, I stated I'm getting a new GPU, just need a setup that works in an emergency when things go south and I need a boot screen.

Pre-boot configuration via EnableGop injection to the GPU or to the Mac Pro BootROM now works perfectly for any UEFI GOP GPU.

No need to have an AppleOEM GPU anymore except to run AHT/ASD complete tests.

 

[theMotoMan]

No it's not. It's a DP1.1 GPU that is extremely limited with anything over 2560x1600, the greatest resolution that still have an acceptable refresh rate.

WQHD@30Hz have almost the same bandwidth requirements of 2560x1600@60Hz, but 30Hz is not enough for most people. If works acceptably for your workflow, good enough.



Pre-boot configuration via EnableGop injection to the GPU or to the Mac Pro BootROM now works perfectly for any UEFI GOP GPU.

No need to have an AppleOEM GPU anymore except to run AHT/ASD complete tests.

When I get my new GPU, I’ll definitely apply the GOP patch.

According to my screenshots, both displays are running at 60 Hz, not 30. Am I missing something?

 

[tsialex]

When I get my new GPU, I’ll definitely apply the GOP patch.

According to my screenshots, both displays are running at 60 Hz, not 30. Am I missing something?

When you have limited bandwidth, something has to give. Could be color space, refresh rate, resolution - SwitchResX will show.

Btw, you don't have exactly 60Hz, you have NTSC 59.88Hz.

 

[theMotoMan]

When you have limited bandwidth, something has to give. Could be color space, refresh rate, resolution - SwitchResX will show.

Btw, you don't have 60Hz, you have NTSC 59.88Hz.

Got it. NTSC would be interlaced, so basically 30 fps?

 

[tsialex]

Got it. NTSC would be interlaced, so basically 30 fps?

I don't know if this resolution is really interlaced, is a very unusual one. NTSC there could be just for the HSync/VSync compatibility and not to differentiate progressive from interlaced, you are connecting via HDMI.

The DP1.1 have a limited bandwidth of 8.64Gbit/s, you also have to transport video and audio inside this, so, is even less than that for the video signal. When you use a resolution greater than 2560x1600, something have to give to be inside the total available bandwidth.

 

[theMotoMan]

So I finally received the "Active" mini DP to HDMI adapter and got some interesting results. I am getting a better GPU, so this info will eventually not be useful to me, but I am documenting this for others attempting anything similar to me to start out with.

The good:
1. The HD 5770 drives the LG Ultrawide well at 3440x1440 at 60Hz; it looks fantastic for browsing, etc.
2. It even drives it at 3840x2160 (UHD) at 30Hz, but not optimal.

The bad:
1. Since the boot rom uses DP 1.1, it doesn't play well with the active DP->HDMI adapter and just shows rolling static until the OS boots, then it renders properly.
2. I had hoped this would be a solution to be able to see the boot screen with the stock HD 5770 card while attached to my modern 35" LG Ultrawide, but alas, the only thing that is working is a DVI->HDMi cable that only supports 1080p.

DP 1.1 max bandwidth is 10.8Gb/s and 3440x1440 takes about 8.92Gb/s, so it fits within the spec.

Here is a nice bandwidth calculator

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