Comment by elabajaba | Hacker News Reader

Comment by elabajaba | Hacker News Reader

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We also just didn't have any good ways of driving such high PPI displays until recently without having to resort to janky hacks like dual cable setups (and the lines down the middle that those tend to have).

A lot of laptops still don't support HDMI 2.1, and DP 2.0/2.1 only just came out (and I don't know if any displays are using it yet). There's also the bullshit the HDMI forum pulled where they relabeled HDMI 2.0 as HDMI 2.1 (years after HDMI 2.1 was out and established as "the one that can do 4k120hz no chroma subsampling" (a lot of implementations were around 40Gbps instead of the full 48Gbps because it was cheaper, and they didn't need the full 48Gbps for 4k120hz 10bit)), despite them having hugely different specs.

Displayport 2.0/2.1 is also a clusterfuck because they decided that it would max out at either 40Gbps or 80Gbps depending on the implementation (DP40 and DP80), and companies don't generally tell you what their implementation actually supports.

Macbook Pros only got HDMI 2.1 this year, iirc base and airs still don't have it. Intel iGPUs only do HDMI 2.0 and DP 1.4, AMD's Zen4 laptops can do HDMI 2.1 and DP 2.1 (idk what bandwidth). For dGPUs, AMD's 6000 series is HDMI 2.1+DP 1.4 (but there are issues with DSC), while 7000 series is HDMI 2.1 and DP 2.1 (DP80). Intel Arc dGPUs are DP 2.0 (DP40) and HDMI 2.1. Nvidia's 30 and 40 series are HDMI 2.1 and only DP 1.4.

edit: Also, people don't realize just how fucking huge an 8k framebuffer is, and you need multiple for a swapchain. Even for just basic 8bit colour you're looking at ~133MB per framebuffer.

Great comment. I just bought a new Dell 6K display and I'm struggling to imagine a purpose for 8k, but it's incredible that we have the technology to drive that.

> I just bought a new Dell 6K display and I'm struggling to imagine a purpose for 8k

It's for large monitors. I run a 43" 4k tv as a monitor. I would absolutely benefit from a similar sized tv in 8k. And people who run closer to the 50" size would benefit even more.

I think you're probably right about traditionally sized monitors, though.

> janky hacks like dual cable setups

I’m a bit surprised we don’t see point-to-point ethernet cables doing this. They are standardised, reliable, and carry a lot of data. My napkin math says an 8K display at 40 bits per pixel and 60 fps is about 18 Gbps, well into the range of fancy ethernet.

And, if consumer electronics can drive down the costs of these interfaces, everyone wins.

Your math is significantly off here. That's about what it takes for 4k60. 8k60 10bit takes about 80Gbps.

Oops. I blame the napkin.

Anyway, with compression it should be a piece of cake. I never quite understood why HDMI even streams pixels and not refresh instructions.

> ~133MB per framebuffer

That's not a lot for people in the market for 8K monitors. 24G VRAM in the form of used 3090 cards is way cheaper than high end monitors. But yeah lack of DP2.1 support on current-gen cards like the 4090 is a problem

> you need multiple for a swapchain

There should be just two with variable refresh rate

On an 8GB (eg. base Macbook) or 16GB laptop where you're sharing ram between the CPU and iGPU it's a ton.

People want 8k for better PPI for text rendering, not for games, meaning they want to use it with their work laptop.

> There should be just two with variable refresh rate

There's still a lot of software out there that's using DXGI blit model instead of DXGI flip model, and a triple buffered vsync+windowed blit app means you're looking at 5? framebuffers in flight at once. (ignoring any additional intermediate buffers for each app, and potentially having multiple overlapping windows drawing onscreen at one time).

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