HP z27 4k monitor with 2013 iMac 27" has glitchy screen

[austriker]

I'm trying to use my HP z27 4k monitor (27") with my late 2013 iMac but it's not cooperating.

Cable: Thunderbolt 2 (mini Displayport) to Displayport.

I've used the same exact cable on my 2014 macbook pro and it works fine.

But when I use it on my iMac the display has lines going through it - it looks very glitchy with lines going through it and the colors totally off. Picture:


(Looks like hp forum photos arent working, so here's a link: https://imgur.com/2ZxlV3ahttps://imgur.com/2ZxlV3a)https://imgur.com/2ZxlV3a

Here's the hardware settings on the imac:

(Looks like hp forum photos arent working, so here's a link: https://imgur.com/2ZxlV3ahttps://imgur.com/JcBpkGKhttps://imgur.com/JcBpkGKhttps://imgur.com/JcBpkGKhttps://i.imgur.com/JcBpkGK)


When I use a miniDP/TB2 cable to HDMI the glichy vibes go away but the resolution is really low:

(link if photo doesnt load: https://imgur.com/sNGDGJBhttps://imgur.com/sNGDGJBhttps://i.imgur.com/sNGDGJB)

Here are more details on the cables Im using:

MiniDP to DP: https://www.amazon.com/gp/product/B087QFDYP6/

MiniDP to HDMI: https://www.amazon.com/gp/product/B07ZYSS2K2/

Do I have a broken cable? Has anyone else out there connected a late 2013 imac to the HP z27 successfully? If so, what cable did you recommend/use?

Thanks so much, this is driving me crazy!

Apple's TB2 to TB2: https://www.apple.com/shop/product/MD861LL/A/apple-thunderbolt-cable-20-m

(I tried this TB2 cable but it doesnt seem to send any signal)

I have reset the SMC and NVRAM on the iMac.

[SPaulMac]

I am having the same problem with my z32 connected to my late 2013 iMac. Distorted screen and off colors. The connection (using a mini Displayport to Displayport cable) to the Thunderbolt port farthest from the Ethernet port wouldn't sync correctly, but moving it to the other Thunderbolt port at least causes it to connect at 4K 30hz, however it does not fix the glitches.

Any help would be greatly appreciated. If this monitor is not capable of connecting correctly with the late 2013 iMac, I will need to return it and look for a different option.

[austriker]

Gosh thats concerning. I've tried new mini DP to DP cables since my original post but they do the same glitchy thing. So its not the cable.

So it seems the issue is the iMac for some reason. Whats odd is that the cable works fine for full resolution on my old macbook pro which I think is around the same year as my iMac.