Question Crash issue after upgrading to 4k monitor

[caribou123]

Hello,
I own a Dell Optiplex 780 SFF with an upgraded CPU (4 cores) and a small GPU (AMD HD Series 7000 1Gb). 2 Days ago I bought a 4k monitor to connect my macbook pro (usb-c hub), and replace my old VGA monitor.
With the macbook pro I encounter no issue, it works perfectly. With the Optiplex on the other hand.. I connected it via a Display Port cable to the monitor, first all works fine, than I tried to set a 4k wallpaper, computer crashed (never had crash issues), after that I had trouble turning it off, led blinking, fans blowing, I let it rest for the night, on the morrow same problem, led combinations indicated memory issue so I tried remove the ram and tried each bar one by one, nothing changed.
Than I decided to remove the GPU, the computer boots and I can have display via my old VGA monitor. I cleaned up the GPU, put it back, all works (for know I guess).

Still I have a weird issue, Ubuntu is installed in dual boot with Windows 10, when I use my VGA monitor I can see the grub page (Windows being default), when I plug the 4k screen I cannot and Ubuntu starts (instead of W10). So in order to use W10 I need to use my VGA monitor, start W10 and then switch to 4k.

Can all this be caused by a SSD corruption ? Or did the monitor somehow blow up my GPU ? The GPU is definitely weak, so the little lag I have with the mouse or the refresh rate stuck at 30 Hz I can understand, but why would the computer crash ? Can the monitor be 'defective' ?

If it's just a GPU issue I can upgrade to something more suitable (any recommendations ?). But I would like to be sure.

Thank you in advance for your help,

Arthur

 

[caribou123]

Anyone ?

 

[PC Tailor]

Do you have a minidump or event viewer report for when the crashes occur?

 

[caribou123]

Thanks for your answer ! Nope it crashed only once, after I started the computer the first time (with the new monitor), after this crash I had trouble to power on my computer (fan.. led..). I fear that it might happen again and I would like to prevent it. Now I deleted Ubuntu and Grub and set the resolution to 1080p, it works for now. My graphic card is not meant for 4k, can that have caused the crash ? it's an AMD radeon hd 8490. How can I be sure that the display is OK (might be a bit paranoid, but since I will connect a lot my MB pro to it, it would like to be sure) ?

 

[PC Tailor]

If your GPU is overworking, then you could be causing crashes yes.
Equally your GPU overworking and having a poor quality PSU could suggest the power issues.
Keep it at a resolution that it's capable of performing at - you don't have the GPU to run it at 4k - and equally I would suspect like most Dell Optiplex - the PSU quality it probably sub standard.

 

[caribou123]

Would it help to change my GPU to the GTX 710 (2gb, support uhd, low-profile) ? Could you please also confirm that it cannot be the screens fault ?