Most 5120×2880 monitors (e.g. Dell UP2715K, HP Z27q, iMac 5K, LG UltraFine 5K) are driven via two discrete DisplayPort 1.2 connections, each handling one half of the screen (2560×2880). (In the case of the UltraFine, the two connections are tunneled over Thunderbolt 3). My point is - theoretically, any GPU with two DisplayPort 1.2 outputs should be able to handle 2× 2560×2880 to get 5120×2880. Case in point - I was driving my UP2715K from an NVIDIA NVS 510 for some time. That's pretty much a glorified GeForce GT 630, i.e. probably the weakest card out there that meets this requirement and it was fine at the pixel-doubled mode. Scaling would, of course, have been an entirely different matter.Secondly, 5K is very hard to drive (14 MP vs 8 or 9MP). It's only in the past few years that the majority of external GPUs can handle that.
There are also some 5120×2880 screens (e.g. Iiyama XB2779QQS, Planar IX2790) driven via a single DisplayPort 1.4 connection (and thus restricted to 8 bpc). Both AMD and NVIDIA GPUs released in 2016 or later support DP 1.4. Intel, though, only added this with Ice Lake (2020). My point is - merely driving 5120×2880 from a discrete GPU (external or not) has been possible for years.
In addition to the reasons mentioned, another is... (presumably) because there's not a high demand for them outside of the macOS world. The majority of users are happy with a "4K" screen of around 27 inches, i.e. around 160 ppi, because they run Windows and its fractional scaling works and looks great.Btw any ideas why there are almost no 5k monitors on the market
What laptop is that, just out of interest? What CPU/GPU?I have a mid-range laptop bought in 2020 that can only do 4K.