Learnings after buying a 4K monitor - Mojave

So I had been in the market for a 4K monitor for a while now.. After some thorough research and Gumtree scouting, I came across an LG 27UD69 which I managed to get for £220.

One of my huge wants was the scaling macOS performs with high res monitors - I made a post about this a few days back and received a lot of positive feedback on the support of multiple monitors for HiDPI scaling, so thanks to all 4K monitor owners that replied!

I thought I'd list in this post some of my learnings which I wasn't aware of before I went down this road (maybe some of them will be very obvious to you, but thought I'd share if someone is on a similar path - my GPU btw is an RX 570 by Sapphire.)

1) Use DisplayPort! It is true that HDMI 2.0 supports 4K @ 60Hz but to my great surprise the quality of scaling that macOS performs and overall the colours and picture was severely impacted when I used HDMI! A benchmark I recommend you to check out is how the red and yellow (close/minimise) bubbles look in any given window. Using HDMI had clear aliasing which is now not present with DisplayPort. This is also evident just by using Chrome for a minute, everything just looked pretty awful with HDMI! I also tested this with Windows 7 and everything looked fine there, so I'm guessing it's a macOS thing.

2) If you read DisplayPort 1.2 compliant on Amazon, eBay, or any online store for a DP male-to-male cable, that doesn't necessarily mean that it will support 4K @ 60Hz. I understand 1.2 is supposed to support HBR2 (17.28 Gbit/s) but look out for explicit bandwidth specifications, actual data rates and/or explicit stating of compliance with HBR2.

https://en.wikipedia.org/wiki/DisplayPort - A very cool read by the way.

I had purchased an Amazon Basics DP to DP lead which was advertised as 1.2 compliant which worked with my previous 2560x1440 monitor. I thought to myself I could upgrade and keep the same cable and all would be fine but it was a horrendous experience. Constant blacking out, flickering, and getting stuck at 30Hz.

This led me to purchase a HDMI 2.0 cable to ensure that the fault didn't lie with my monitor's DP connection, which enabled me to discover learning 1).

I ended up ordering a few DisplayPort cables during my search for an actually functional one, so I'll post a lil link compilation here:

https://www.amazon.co.uk/gp/product/B07GGVJDQR/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 - 3 meters long and works perfectly @ 4K 60Hz

https://www.amazon.co.uk/gp/product/B01AWFUTYO/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 - 5 meters long and works perfectly @ 4K 60Hz (I'm currently using this)

https://www.amazon.co.uk/gp/product/B01J8S7EXU/ref=ppx_yo_dt_b_asin_title_o05_s02?ie=UTF8&psc=1 - Amazon Basics cable - 4.56 meters long and DOES NOT work @ 4K 60Hz even though it states to be DP 1.2 compliant.

3) Cable quality actually matters - I was always the guy that would take the piss out of expensive digital cables (I mean if they are ridiculously priced I still will haha), but to my great surprise I quote the following:

"The transmission mode used by the DisplayPort main link is negotiated by the source and sink device when a connection is made, through a process called Link Training. This process determines the maximum possible speed of the connection. If the quality of the DisplayPort cable is insufficient to reliably handle HBR2 speeds for example, the DisplayPort devices will detect this and switch down to a lower mode to maintain a stable connection.[8](§2.1.1) The link can be re-negotiated at any time if a loss of synchronization is detected."

I'm still not sure whether the Amazon Basics cable I have been complaining about actually was HBR2 compliant but of really poor quality and consequentially unable to maintain HBR2 bitrates...

TL;DR - 1) Use DisplayPort instead of HDMI, it can solve scaling issues, colour issues, and generally display issues. 2) Make sure that before you buy a DP cable to ensure that the product listing explicitly states that the cables handles a data rate of 17.28 Gbit/s or that it is HBR2 Compliant, or at least that it will support 4K @ 60Hz. 3) Cable quality matters - through DP's Link Training, if the cable's quality is shit, the DP devices will detect this and downgrade the bitrate, disallowing 4K @ 60Hz.

Hope this helps anyone that is after a 4K monitor and sorry if it was too obvious to some people!

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