DVI output for Radeon HD 4000 series cards

Posted by Hans de Ruiter

I am pleased to announce that the RadeonHD driver for AmigaOS 4.x can now also output to DVI on Radeon HD 4000 series cards. Apart from being another item ticked off the driver development to-do list, from a personal perspective this means that I can now use my 4-port DVI KVM switch fully. Previously, switching to my Sam460ex would mean the monitor switching to the VGA output, and then manually switching to DVI again when switching back to another machine. The button on my monitor for switching inputs has already lost its "click" sensation due to the large amount of switching, so I am glad to hand that task over to the KVM.

My hopes that adding DVI output would be a "quick fix" were quickly dashed when fixing what I thought was the cause resulted in no change. The task quickly became a needle-in-a-haystack hunt; nay, multiple needle-in-a-haystack hunts for what AtomBIOS functions had been added or changed, and where to get the additional data that was needed (the AtomBIOS is undocumented). The AtomBIOS' API is tightly coupled to the hardware, meaning that new functions are added, and old ones get new versions (functions have version numbers so that they can be changed at will) with new inputs and outputs. One by one, changes were tracked down and added to the driver, most often without any noticeable change. As you can imagine, working hard and getting seemingly no result is very frustrating. At one stage I even lost VGA output, thanks to an introduced bug that was later tracked down and fixed. Eventually, the behaviour of the DVI output started changing/improving, giving a much needed motivation boost to fix the remaining problems and get it working properly. With one final compile and reset, the DVI output showed the AmigaOS 4.1 boot picture, and just worked.

Comments (11) | 6 May 2011