I have a Tyan R9000 pro.
I find DirectX8.1's HAL StencilCaps is empty,and I run the DirectX8.1 SDK example -Stencil Mirror,it can not run under the HAL.
It should definitely support such a basic thing. Try making sure you're running in 32-bit. Also, I've seen other people reporting that the CAPS are incorrect. Try to see if you can bypass the CAPS check and see if it renders anyway.
I found the R9000 only support D3DFMT_D16,D3DFMT_D24X8 and D3DFMT_D32 DepthStencil Buffer in my pc.
I try to use D3DFMT_D24S8 or D3DFMT_D15S1 to CreateDevice,but the function return error.