brentdc-nz/pcsx-reloadedx

A Xbox port of PCSX-Reloaded with hardware rendered graphics. Stable repo i.e. only thoroughly tested optimizations are merged(testing still in progress).

pcsx-reloadedx's Issues

Xbox supports immediate mode rendering

https://github.com/marty28/PCSX-ReloadedX/blob/08d568c3e1be175bd52fbc736f94553ca0b41f4b/xbox/fakeglx/fakeglx09.c#L980-L988

This is not true for Xbox Direct3D. The Xbox GPU (NV2A) supports immediate mode rendering.
Microsoft added hardware extensions which should be available as:

• D3DDevice::Begin
• D3DDevice::SetVertexData4f and friends
• D3DDevice::End

The mapping is the one that you'd expect from the nvidia OpenGL implementation; vertex attribute 0 submits the vertex (equivalent to glVertex4f).

The data would be inlined into the pushbuffers. You can avoid the call overhead, by constructing a custom pushbuffer from scratch to get zero-copy for extra performance. You can then use D3DDevice::RunPushBuffer or something to submit it.
Wether this is faster: I don't know. It certainly depends on what kind of data you submit.

Also check @xqemu code or nxdk source-code for more information. @XboxDev community in general will have knowledge about this (although we might not always know what's best for performance yet).