GPU DirectX Support

[ArmatageShanks]

I have a silly question, I'm busy watching a random video and the mention of the old GeForce GTX 280 reminded me of a couple of years ago I saw one for sale for a grand, this card cost 5k when it came out I believe, if I did my math correctly. So I had no GPU then and thought to take advantage of the deal and get my first ever flagship gpu, an old one but nevertheless.

I ended up not going for it because of the lack of DirectX 11 Support

Now for the question, I know DirectX support is linked to the GPU hardware and as such it is not possible to have previous generation Gpu's support newer dx versions.
What I want to know is why not, is there some physical hardware required to make this possible, if so can it not be emulated at gpu level or is this simply a case of development of the new api to interface with previous gpu generation would take from the current development too much resources to be viable or simply not making sense business wise for generating sales on the new stuff.

I'm guessing its hardware level as I have never heard of anyone making direct x run on a gpu that it wasn't built for.

 

[ponder]

Direct3D API versions have related hardware requirements. I can't see something like msaa being efficiently implemented via software hence the dedicated hardware on gpus.

https://docs.microsoft.com/en-us/windows-hardware/drivers/display/hardware-requirements
https://en.wikipedia.org/wiki/DirectX#Compatibility

 

[cguy]

^ as @ponder says. Surface format requirements, shader instruction requirements, texture filtering requirements, texture format requirements, etc. evolve and would be 100’s of times slower to emulate in software. Then there are also system requirements, like supporting virtual memory for security, page faults, mappable GPU memory, PCIE BAR size, etc.