According to a recently discovered entry on Intel's support pages, the Arc series graphics cards no longer have native support for DirectX 9. However, applications based on it can be run via the D3D9On12 interface. A popular example of a DX9 game is the shooter CS:GO.
@SquashBionic draws attention to the said entry on Twitter. @OneRaichu had previously provided hints in this direction, which are now confirmed.
Intel states that both the integrated GPUs of the Alder Lake processors (Core 12th Gen) and the discrete graphics cards of the Arc family “no longer natively support D3D9”. However, applications and games based on DirectX 9 could “continue to run via the Microsoft D3D9On12 interface,” it said. Older processors from Intel still support DX9 natively. However, if these are combined with an Arc graphics card, then a game will probably also use D3D9On12, Intel continues.
12th generation Intel processor's integrated GPU and Arc discrete GPU no longer support D3D9 natively. Applications and games based on DirectX 9 can still work through Microsoft* D3D9On12 interface.
The integrated GPU on 11th generation and older Intel processors supports DX9 natively, but they can be combined with Arc graphics cards. If so, rendering is likely to be handled by the card and not the iGPU (unless the card is disabled). Thus, the system will be using DX9On12 instead of DX9.
Since DirectX is property of and is sustained by Microsoft, troubleshooting of DX9 apps and games issues require promoting any findings to Microsoft Support so they can include the proper fixes in their next update of the operating system and the DirectX APIs.
D3D9On12 is open source software that translates graphics commands from D3D9 to D3D12 and practically acts as an alternative GPU driver. Compatibility is thus maintained in a roundabout way. However, Intel expressly points out that any problems with DirectX 9 applications are now Microsoft's sole responsibility and that appropriate support requests must be made in this direction.
To what extent this DX9 support indirectly impacts performance versus a native implementation is unclear. Microsoft speaks of a “relatively high-performance implementation”.
However, the circumstance is not too serious, because most reasonably up-to-date games (additionally) use a newer API such as DX11 or DX12. As a figure published by LinusTechTips shows, most of the currently popular games use a newer API or offer a newer one alongside DX9.
However, has showed that Intel Arc also has major weaknesses in DX11. It runs much better under DX12.