No, HDMI 2.1 doesn't matter (yet) because there are no 8K desktop monitors (meaning 32-inch size or similar) on the market that use HDMI.
The only 8K monitor has for years been the Dell UP3218K, which uses DisplayPort -- and requires two DisplayPort cables, actually, to get 7680 × 4320 at 60Hz.
Apple has never supported this on any of their machines -- they just couldn't drive the monitor. (It worked, but only in 4K mode.)
They quietly changed this with the M2 machines. I had a MacBook Pro M1 Max that couldn't drive this monitor at 8K. Then I found this GitHub thread[1] where it was revealed that M2 Pro can drive up to one of these 8K displays over Thunderbolt (to DisplayPort). And the M2 Ultra on a Mac Pro or Mac Studio can drive 3 of them.
I don't think it is scaling, per se, but rather that Apple has never supported the full DisplayPort spec. That 8K monitor apparently needs support for something called "dual SST" and Apple never supported that in their software. More details are in the linked GitHub discussion.
So, I don't know why they didn't make this work on the M1 Ultra, too, but Apple gonna Apple. So I went down to the Apple Store and bought a Mac Studio M2 Ultra the day I read that. Now I can plug my Mac into my KVM switch and use this monitor on Mac just like I always could with Linux and Windows.
The only 8K monitor has for years been the Dell UP3218K, which uses DisplayPort -- and requires two DisplayPort cables, actually, to get 7680 × 4320 at 60Hz.
Apple has never supported this on any of their machines -- they just couldn't drive the monitor. (It worked, but only in 4K mode.)
They quietly changed this with the M2 machines. I had a MacBook Pro M1 Max that couldn't drive this monitor at 8K. Then I found this GitHub thread[1] where it was revealed that M2 Pro can drive up to one of these 8K displays over Thunderbolt (to DisplayPort). And the M2 Ultra on a Mac Pro or Mac Studio can drive 3 of them.
I don't think it is scaling, per se, but rather that Apple has never supported the full DisplayPort spec. That 8K monitor apparently needs support for something called "dual SST" and Apple never supported that in their software. More details are in the linked GitHub discussion.
So, I don't know why they didn't make this work on the M1 Ultra, too, but Apple gonna Apple. So I went down to the Apple Store and bought a Mac Studio M2 Ultra the day I read that. Now I can plug my Mac into my KVM switch and use this monitor on Mac just like I always could with Linux and Windows.
[1]: https://github.com/waydabber/BetterDisplay/discussions/199#d...