GeForce FX + Pixelshader 2.0

[cthellis42]

I've heard a but of guff out there as to whether or not the FX family has full and proper PS2.0 support (which is necessary for full DX9 compliance) but can't remember now what I was reading, where, or whether this is anything but a curiosity right now.

I figure if there's any place to inquire for more information about this and get some links and such to get facts straight, this would be it. ^_^

 

[3dcgi]

Your best bet is to search through old forum topics.

 

[cthellis42]

Already tried, as I thought I heard mentions on here, but I couldn't find anything relevant with a number of combinations. I'm gettin' all flustered now just trying to remember what I read and where. Ugh... -_- Just figured since most folks keep on top of EVERYTHING offhand, they might know what I'm thinking of. Hehe...

 

[Dave H]

In hardware: Yes, it does. In fact, it is fully PS 2.0_extended compliant.

In software: Yes/sort of. For a long time, the drivers would make a compliance tradeoff (a.k.a. cheat) and automatically use FP16 even when the spec called for FP24 or better. (According to the spec, FP16 is ok in a PS 2.0 shader only when the shader explicitly says so.) AFAIK this behavior is gone from recent drivers.

Also the FX series is weak in supporting a couple of DX9 features; in particular their support for MRT (multiple render targets--basically a scratch space where you can render something in order to read back and use later, rather than in order to display directly; this is useful for many effects) is much less flexible than that of ATI's DX9 parts. I'm not sure if this is an issue that is built in to the hardware or could be fixed by later drivers. (I think the latter, but then again they haven't fixed it yet.) In any case, it's optional for DX9 compliance.

(The FX series has bad performance running PS 2.0 shaders compared to ATI's parts, but that has nothing to do with compliance.)

 

[rubank]

cthellis42, is this the thread you were looking for?
http://www.beyond3d.com/forum/viewtopic.php?t=6837