Anonymous sources claim XB1 has 'heat issues'
I'm not much for rumors at all, but considering the first Xbox also ran quite hot (50/60+ degrees)
And the first 360 models also ran extremely hot.
I won't be surprised if this is actually true.
The GPU/CPU combo in the XB1 along with the XB1 design allows for insufficient heat disposal.
So instead of another RRoD fiasco, MS decided to underclock the console by 200Mhz as a quickfix.
What does this mean to developers?
Well we already know that the PS4 is more of a powerhouse than the Xbox One. It has faster RAM and bus bandwidth than the Xbox One already. Under clocking the system will widen the gap between the two consoles, but at the same time will keep the failure rate on the Xbox One very low. The last thing we need is another RRoD fiasco.
In terms of games, you will see a significant difference in multiplatform titles. Lower clock speed means lower frame rates. This means that a game running 60fps on PS4 may only run at 30fps on Xbox One. Even given the current specs, this would probably still be the case except now we are under clocking the GPU. This could affect other things like the Peak Shader Throughput.
If Minecraft were to be released for both Xbox One and PS4, you'd see no difference. A game like Battlefield 4 my run at a lower framerate on the Xbox One than it does on the PS4. We still don't know how much the eSRAM is going to boost or hinder performance of the Xbox One.
We also can't leave out the fact that every developer, every game and every engine runs differently. They could theoretically boost frame rates on the Xbox One to match PS4 by turning off AA effects and lowering resolution.
Ofcourse this is a rumor and can only be confirmed by ripping apart the console and testing busspeeds etc after the launch.
If later XB1 models run faster then the first ones then it can be confirmed as true.
Source:360Crunch