GDI has been accelerated. Does anyone know when this happened?

Question

To sketch the background of this question : at work we use Dell Precision workstations. My current one has got an NVidia Quadro FX1700. My team is developing the graphics components for a real time data acquisition system. So we are always looking out to see if the graphics operations don't use up too much CPU time. For quick checks, we have a couple of test programs that we run, which draw scenes at a specified rate ( e.g. 10 fps ) and we use plain old Task Manager to see where CPU usage is at. One of these programs is heavy on GDI DrawRectangle calls ( which are filled ). This program always used to consume about 40% CPU user-time, but since about a year or so ( just guessing here ) it only uses about 2-3 % kernel-time. So clearly some hardware acceleration is going on here. And indeed, if I turn HW-accell off, we're back to the original 40% user-time. All of this is of course good news, because we were already thinking about going to OpenGL. Year after year GDI never got the benefit of hardware acceleration. Until some time ago that is.

Does anyone know anything more about this? Did Microsoft do this? Or is it gfx-card vendor specific?

Edit

Thnx for the answers already ( Ferrucio, Torlack and Rob Walker ) but my question has not been answered yet. We are talking about a filled rectangle here. Probably the most trivial function to optimize : just send a couple of coordinates to the GPU and let it rip. Yet it was always implemented on the CPU side. So far the answers lead me to believe that NVidia finally saw the light ( after more than 10 years ) and accelerated GDI. And no announcement about this? There's no information to be found on this at all. My internal customers ask me about the speedup of the graphics, and all I can say is "well, we got lucky".

Edit2

It does seem like it is driver related according to the different answers. So, then NVidia has made crappy GDI drivers for its workstation cards for years. It really was an accepted fact within this company that GDI was not accelerated and all the tests confirmed this.

Answer 1

GDI works by calling various functions in the graphics device driver. There are a core set of functions that every driver must implement. Other functions may be implemented by the driver. If they are not, GDI will perform those functions itself.

If a particular function is not implemented in hardware then there is no point in the driver doing a software implementation of that function since GDI can probably do a better job. GDI is extremely well optimized for performance.

As more functions are implemented in hardware, not only do those functions perform much better, but there is also less work for GDI to do, resulting in less CPU time spent on graphics.

It may also be the case that the graphics card vendor, in an effort to get a card out to market quickly, may not have implemented all possible hardware functions that the card could perform. Later versions of that driver may then implement that functionality, resulting in improved performance.

Answer 2

GDI was accelerated for quite awhile. Far as I recall it did depend on your hardware and drivers to some extent. Why you've seen such a jump in performance only recently seems odd.

However, don't get too happy - GDI hardware acceleration is no longer supported in Vista. The new desktop composition engine doesn't support it. However, in Vista you do gain fast moving of windows since content doesn't always have to be re-drawn by the application (and no tearing I think?).