the short answer is "i am not sure"...
The long answer:
Well, back in early 2000 was in use Advanced Graphic Port (AGP) and it used so called "AGP Aperture Size", which could be up to 256mb, and it was the maximum "chunk" of data which could be sent to graphic card.
In 2020, hardware developers realized that PCI-E 3.0 bus or higher can address over 4GB of memory space, and that limitation of 256mb is nowadays laughable, but nobody looked into the issue for almost two decades.
So by the end of the year they released a lot of updates for mainboards (sometimes beta, sometimes full update), graphic cards to enable "Above 4G addressing" and "Resizable Bar" ...
Those two features basically allow to break 4GB memory addressing limitation for PCI-E devices and also to transfer more than 256mb in a single operation. For example 2560mb can be sent as a single chunk so the overhead is at least 1/10th.
At this point, Large Memory space is available to my GPU, o the aperture limitation does not exist on hardware nor OS level.
There are two limits remaining:
a) Graphic driver
I can turn on KMD_RebarMode in registry. It should not need reboot to work, however its oficially unsupported and will revert to 0 upon reboot.
b) Game or 3d engine has to be aware of the feature.
Atm just Cyberpunk 2077.
The only problem is that my Threadripper 1900x and Radeon VII are not on "supported" list, however its only driver which is limiting the usage via registry.
