I want to bring up an issue that hardware review (including AnandTech) sites seem to have overlooked when reviewing graphics cards capable of supporting Dual Head and OpenGL. ATI is especially bad in this respect. I bought a Radeon 8500 when it first came out and while dual head works fine for a basic windows application try running an OpenGL application across both screens (or just the second screen) and failure follows quickly. I just tried the latest Radeon 9700Pro and its Dual Head OpenGL support is even worse (with the latest drivers). It seems that no hardware review sites have noticed these problems thus ATI hasn't bothered to address them. I can forgive a brand new product with a few driver issues but the Radeon 8500? They advertise Dual head support... they don't say it only works in the following cases?
I understand that many(most?) users of these cards use them to play games (and that's great) but they are also capable of more. If you want to see the problem for yourself might I suggest that you try Iview3D - This is a free viewer for our OpenGL based visualization system. It can be found at www.ivs.unb.ca/products/iview3d. Sample data sets are also available. This is an interactive 3D visualization application. It uses a lot of OpenGL features that games typically don't, thus it is very good for uncovering OpenGL driver problems.
While NVidia's Dual head driver support is vastly better it's not perfect although it may be Dell's fault not NVidia's. Take my nice Dell 8200 Inspiron Laptop with a Geforce 440 mobile GPU for example. The divers currently don't support OpenGL on the second display at all under Windows. (It works great with the Linux drivers though.) Until the latest release of the NVidia drivers you had explicitly enable OpenGL support on the second display from the list of options in the Advanced OpenGL tab on the display control panel. (The Laptop omits this option all together....)
Here are a few technical details that might be of interest:
For the ATI 9700Pro
OpenGL on the second head - just non functional period. Note - both heads should be be at the same color depth. If you stretch a window across both displays and interactively move the 3D scene the 2nd display doesn't update and the primary display gets messed up as well. Note that I did the tests with each display at a resolution of 1280x1024.
For the ATI Radeon 8500
Results are better then the 9700Pro but still problematic.
1. Dualhead Issues
- A single OpenGL window can never span the full two monitors. The rendering stops 1 quarter of the way into the second monitor, regardless of the resolution.
- If an OpenGL window is on the second monitor, there are many problems. Calls to glReadPixels do not work, the front/back buffers do not work properly, and rendering stops before all commands are completed.
2. glReadPixels does not work on either monitor and also does not work in single head mode.
I've tried sending this information to ATI but I can't say we've seen any progress. The ATI 9700Pro is a *very* nice card but many of its features are forward looking. Dual head support is a feature for today and tomorrow... and it doesn't work. Does this not seem like a significant deficiency?
Here's to hoping the 9700Pro card will someday work as advertised... but for now its back to the store... sigh
.
Comments? Ideas?
Later,
Mark
I understand that many(most?) users of these cards use them to play games (and that's great) but they are also capable of more. If you want to see the problem for yourself might I suggest that you try Iview3D - This is a free viewer for our OpenGL based visualization system. It can be found at www.ivs.unb.ca/products/iview3d. Sample data sets are also available. This is an interactive 3D visualization application. It uses a lot of OpenGL features that games typically don't, thus it is very good for uncovering OpenGL driver problems.
While NVidia's Dual head driver support is vastly better it's not perfect although it may be Dell's fault not NVidia's. Take my nice Dell 8200 Inspiron Laptop with a Geforce 440 mobile GPU for example. The divers currently don't support OpenGL on the second display at all under Windows. (It works great with the Linux drivers though.) Until the latest release of the NVidia drivers you had explicitly enable OpenGL support on the second display from the list of options in the Advanced OpenGL tab on the display control panel. (The Laptop omits this option all together....)
Here are a few technical details that might be of interest:
For the ATI 9700Pro
OpenGL on the second head - just non functional period. Note - both heads should be be at the same color depth. If you stretch a window across both displays and interactively move the 3D scene the 2nd display doesn't update and the primary display gets messed up as well. Note that I did the tests with each display at a resolution of 1280x1024.
For the ATI Radeon 8500
Results are better then the 9700Pro but still problematic.
1. Dualhead Issues
- A single OpenGL window can never span the full two monitors. The rendering stops 1 quarter of the way into the second monitor, regardless of the resolution.
- If an OpenGL window is on the second monitor, there are many problems. Calls to glReadPixels do not work, the front/back buffers do not work properly, and rendering stops before all commands are completed.
2. glReadPixels does not work on either monitor and also does not work in single head mode.
I've tried sending this information to ATI but I can't say we've seen any progress. The ATI 9700Pro is a *very* nice card but many of its features are forward looking. Dual head support is a feature for today and tomorrow... and it doesn't work. Does this not seem like a significant deficiency?
Here's to hoping the 9700Pro card will someday work as advertised... but for now its back to the store... sigh
.Comments? Ideas?
Later,
Mark
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