RadeonHD: Mobility Chipsets now Supported

Posted by Hans de Ruiter

With the Sam460ex recently going on sale and including the RadeonHD driver, the driver has inevitably been tested on a wider range of hardware. While most hardware is working just fine, two people with a Sapphire Radeon HD 4350 reported (see here and here) that it didn't work with their cards. Most of their screens were filled with garbage. This surprised me as all Radeon HD 4350s tested previously worked just fine. So, suppressing my desire to grumble about people ignoring my recommendations (hey, it wouldn't have happened if you had got a Radeon HD 4650/4670 like I suggested ;-) ), I got to work tracking down the problem.

A quick look at the offending card's PCI product ID revealed that it was actually a Mobility Radeon M92 chipset on the board, and not an RV710, which is what Radeon HD 4350s should have. This explained why all Radeon HD 4350s tested to date worked just fine, while these failed miserably. While this was a clear differentiating factor, it did not explain why it failed.

These cards highlighted two problems, not one. First, there was the obvious problem of the cards not working. However, the driver should have detected the problem, and disabled hardware graphics acceleration, so that the display was readable at least. The cause of both problems lay in the GPU initialisation code. This code checks which chipset the card has, and then uploads the correct microcode and executes the appropriate initialisation. As it turns out, some chipsets - most notably all of the mobility chipsets - were missing, and so no microcode or initialisation was done. A small bug prevented this failure from being detected, and so hardware acceleration was not disabled.

The good news is that I have fixed these issues, and future versions will be able to use these cards. In the mean-time, I strongly encourage people to not buy Sapphire Radeon HD 4350 cards, as some of them will not work with the publicly released driver. Likewise, I discovered that the current driver will not initialise RV740 and RV790 chipsets, so avoid the Radeon HD 4770 and 4890 cards too. I do not expect people to buy these cards for their Sam460ex's, as they will block the PCI port. Nevertheless, you have been warned.

Comments (0) | 28 February 2011