mikeka

macrumors member
Original poster
Jan 31, 2013
42
19
Here's a head scratcher .... can't figure this one out. Mac Pro 5,1, Mojave 14.4, Sapphire RX580 video card.

Video displays fine when using AOC monitors with DVI input. I use DVI to HDMI adapters to plug both monitors into the video card HDMI inputs. Looks great.

However when trying to use a single new Dell monitor with only an HDMI input and connecting to the RX580 using just a standard HDMI cable no video is detected. Doesn't make sense.

Any thoughts appreciated!
 

hfg

macrumors 68040
Dec 1, 2006
3,598
285
Cedar Rapids, IA. USA
That is strange. Just yesterday I added a Sapphire RX580 to my MacPro 5,1 and did a fresh install / migrate to Mojave 10.14.4 and other than the expected no boot video, it is working fine driving a Dell AW3418DW Alienware monitor via the HDMI input.

My 27" 5K iMac is also using that monitor via the DP interface.

Hope you find your problem ...
 

bookemdano

macrumors 65816
Jul 29, 2011
1,424
805
Try a PRAM reset (Boot the cMP, and as soon as you hear the boot chime hold down Command+Option+P+R keys. Keep them held down through three boot cycles [so you will hear three more chimes--takes a couple of minutes], then let go. See if that gets your HDMI port to display.
 

BlackScorpion

macrumors member
Sep 11, 2015
52
12
Englishtown, NJ
Has anyone ever resolve this issue? I'm still having the issue where after wake, only one monitor comes on, I have a MP5.1 with an Asus Radeon rx580. I have both monitors connected to HDMI ports. If the computer goes to sleep only one monitor comes back on, I have to disconnect the wire and reconnect it every time.
 
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Eschers

macrumors member
Oct 27, 2015
76
34
ch
Same here, I have a 28“ 4K Samsung U28E590D(hdmi 2.0) and a 24“ WUXGA Apple LED-Display(mDP to DP) on a RX580 Sapphire Pulse(as Apple recommends it, nevertheless it happens with a 580 Sapphire Nitro+ and a Red Devil RX590)

What does temporarily fix my issue is this: when booting up my MP4,1(5,1) I can hear the fans of the gpu and/or cpu begin to change in rpm right before the screen gets a signal (due to no bootscreen as you all know) and then i quickly turn on the samsung screen manually instead of mac pro signal wake up, then it works just fine without any distortion whatsoever UNTIL the screen goes off(hibernate or screen saving) and from there its impossible to get a clear signal without restarting or pulling cables several times..it drops every 4-5 seconds abruptly and then comes back and so on. Less often I experience a complete black screen

Hopefully someone at Apple sees this and/or has already and a fix in new fw/sw
 

SnakeCoils

macrumors member
Oct 17, 2018
83
42
Italy
I had a similar problem with an old HP display (P222va) on its DisplayPort input: the HDMI signal from the various Radeon (HD7950 Mac Edition and flashed HD7950, HD7970, R9 280x) cards were not detected while the HDMI output from nVidia cards was correctly displayed. My first concern was about a mismatch between the flashed firmware and the video card model but since also the original HD7950 Mac Edition had the same issue the cause should be elsewhere.
In the end I discovered the monitor was the issue and I simply changed the display, with a modern HP 22f display (HDMI and VGA input) that works flawlessy (except the same annoying bug in vertical centering on VGA input when the backdrop is almost black in the bottom part).
Another issue with Radeon video cards is the analog VGA from DVI-I port: it is active during the boot process but becomes black (or out of range) when it reaches the Finder: at the time I solved this issue purchasing a miniDP to VGA adapter and it worked without any problems.
Also, the flashed nVidia GTX 680 DVI-I to VGA worked on the same old HP monitor without problems.
 

obiit

macrumors newbie
Jan 26, 2019
14
9
I have had a few issues with HDMI on my Sapphire Pulse RX580 4gb and an Iiyama 27" where it wouldn't detect at boot. This happens randomly but sleep seems to be okay. I am trying it with Displayport to see if that resolves the issue. With Apple only saying it supports certain revisions of the RX580 there could be problems with the port configuration if your not using one of the "supported" ones?

It could be the old HDMI handshake issue for HDCP if things aren't quite compatible? Try another cable if you have one or change your switch on order?
 

BlackScorpion

macrumors member
Sep 11, 2015
52
12
Englishtown, NJ
I have had a few issues with HDMI on my Sapphire Pulse RX580 4gb and an Iiyama 27" where it wouldn't detect at boot. This happens randomly but sleep seems to be okay. I am trying it with Displayport to see if that resolves the issue. With Apple only saying it supports certain revisions of the RX580 there could be problems with the port configuration if your not using one of the "supported" ones?

It could be the old HDMI handshake issue for HDCP if things aren't quite compatible? Try another cable if you have one or change your switch on order?

Yeah, I tried using a different cable, gave the same issue. I will try a display port adapter to see if that helps. I rarely turn my computer off so, it's not the startup issue. Sometimes it so annoying, unable to get the second monitor going.
 

obiit

macrumors newbie
Jan 26, 2019
14
9
Just to feed back after about a week of shutting downs and sleeps i havn't had a failed start (i.e. no screen display) with a displayport cable. I did read somewhere (and only once) that mac's prefer displayport rather than HDMI perhaps it's actually true!? I am only using one monitor so that could be the reason it works?
 

h9826790

macrumors P6
Apr 3, 2014
15,280
7,575
Hong Kong
Just to feed back after about a week of shutting downs and sleeps i havn't had a failed start (i.e. no screen display) with a displayport cable. I did read somewhere (and only once) that mac's prefer displayport rather than HDMI perhaps it's actually true!? I am only using one monitor so that could be the reason it works?

From memory, Apple never sell HDMI monitor. Thundetbolt, mDP, DVI, ADC, VGA...., but not HDMI.

I won't be too surprise if HDMI has worst support in macOS.
 

freqrider

macrumors regular
Feb 10, 2019
116
47
Just to feed back after about a week of shutting downs and sleeps i havn't had a failed start (i.e. no screen display) with a displayport cable. I did read somewhere (and only once) that mac's prefer displayport rather than HDMI perhaps it's actually true!? I am only using one monitor so that could be the reason it works?

Funny, I have the exact opposite results. HDMI works fine on my RX 580 Saphire Pulse, no DP? 3,1 running Mojave. My flashed GTX 1070 worked fine in High Sierra, DVI, Hdmi, Displayport. Should have never ‘upgraded’.
 

guinesscrowley

macrumors newbie
Mar 21, 2010
7
0
Just adding my 2 cents to this....

I have a Mac Pro 5,1 with a Saphire Pulse RX580 running Mojave.

I cloned the bootcamp volume from my Mac Mini to an SSD and tried to boot my Mac Pro just to see what would happen. I knew it was "technically" not supposed to work... but I got bored.

The Mac booted to a black screen with some white prompt text warning me that no boot volume was available.

So I shut down and pulled the sled with the Bootcamp SSD on it and then my Mac was booting to a black screen for a bit but a VRAm zap fixed things.

So... Now my Mac is experiencing a problem with dual HDMI output. If I boot with one HDMI connected it boots fine. If I boot with two connected it boots to black screens. I have to pull the second HDMI and then I see my first screen and then when I plug the second HDMI in I get the second screen.

To be fair, I always used the Display Ports on this card and only just started using the HDMI when I started using the Mac Pro as my secondary system. The Mac Mini was using the Display Ports.

Also, this card did initially go back for repairs as the original, which had a dual bios switch, was acting weird.

This replacement card that they sent me, with that dual boot bios switch removed, may have some kind of problem with it. Not sure. It has worked fine for over a year now... till I did the bootcamp thing.

The display ports still work fine. And the HDMI works fine once I get the system booted and reseat the HDMI cables.

Thoughts? Could the windows boot attempt have jiggered something or is this just an issue that I am just noticing?

I swear I was using both the HDMI with no issue before the attempted windows boot but could not swear to it.

Anyway, that's my 2 cents... thanks.
 
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