W1zzard, you should really modify the wording in all your R9 and R7 reviews where you state:
This is misleading. The 280, 270, 260, (and presumably 250) are the same dies as their predecessors and have three TMDS links but still two TMDS clock generators. AMD has only modified their VBIOS so that two TMDS displays with the same timings can share the same clock generator. Even then, AMD software limits this capability to only work when all three TMDS outputs have the same clock signal.
This means that you can only use all the outputs when you have three identical TMDS monitors.
NVidia's solution is much more flexible since it has three clock generators and three TMDS links, so all the displays can be mismatched without issues. The current phrasing implies that AMD has similar display output capability as NVidia, which is not true. With mismatched monitors, AMD cards can still only use two TMDS outputs. I suspect it may cause a few headaches for people who buy these cards expecting all the outputs to work with mixed monitors when in reality they won't. Maybe the R9 290 series will fix this problem.
Sorry to resurrect the thread but the R9 280x is still fairly relevant and this is one of the pages that comes up when searching for 3 monitor issues and TMDS on the Asus R9 280x.
I was using the Asus 7790 with the following setup : 1 DVI 24" 1920x1200, 1 VGA to DVI 24" 1920x1200, 1 HDMI 17" 1280x1024. ( My Acer has a weird issue it doesn't wake from monitor sleep in DVI, I have to cycle power to get video output, but the VGA seems to work correctly). The R9 280x seems to have the exact same output ports, however the same 3 monitor setup does not work. I can only get 2 monitors to work at a time. I bought the card used so I didn't have all the cables, ordering the OEM active miniDP to DVI cable from ebay hoping it will enable a third monitor, but just annoying that I had to buy an adapter for it raiding up the total cost of the card. I find it really weird that the exact same setup worked on the 7790 but not the 280x and miss my third monitor. From all the descriptions they should both have two TMDS enabled, and the two 24" should use the same clock, and the third should get to use the second clock, but some cards only work with all the same clock/size monitors? I don't know if its a physical limitation or firmware limitation on the 280x, or driver limitation since it was enabled by drivers later in release for the 7790.
Also weird that the miniDP to DVI cables are fairly cheap for being active, the OEM ones for the 280x (as I type this I realize its for the MSI version of the card, the ASUS requires a normal sized DP to DVI adapter cable, with an active one being quite expensive for what it is ).
