There is no reason the monitors should have anything to do with this, so I don't understand what exactly nvidia and ATI (I haven't gotten a chance to try ATI's new implementation, but I know nvidia's does work in all cases...probably because of the monitor used). This should be all that needs to happen for it to work always:
The driver knows the native resolution of monitor, or can be told it.
When the option is set, the driver intercepts any resolution image to send to the monitor , say 1024x768...pastes it onto a black image of the native resolution dimensions and sends that combo to the monitor.
For fixed aspect ratio, it just scales up to the largest dimension, then pastes it and sends that to the monitor.
I can't see any reason why this wouldn't work in all cases, or that it isn't possible? Who cares what the monitor does with other resolutions...just send it native resolution, pre-processed, all the time so the fucking thing can't screw it up. Doesn't the video card just send the frame buffer to the monitor? So just write what it wants to hear in the frame buffer...and who else besides the video card driver can do that?
Frankly, I don't even know why you'd need DVI to make that work.
Its retarded that we're at this point. Almost everyone buying these video cards has an LCD monitor these days. And almost no monitors use a 4:3 aspect ratio! There are a few, but their numbers are dwarfed by the amount of people using 5:4 and 16:10 screens. Few of these screens have scaling options. And yet, here we are...years after their adoption and ATI just barely has finally tried a swing at it and nvidia breaks their half assed implementation as often as they fix it. This isn't some minority game performance issue on a 10 year old title here either...its an issue that affects the majority of their customers across all titles without native support for different aspect ratios. Including newer titles like BF2.
Again, I have not yet tried ATIs new implementation...so maybe they've figured it out? The centered timings option is the only thing available for my x800...it only works on a few resolutions that most games don't use. But I give nvidia no such pass.