Thats where the processor sits. If u open the back cover u can feel it at the back more directly behind the screen. Have u ever used a smart phone before? I ask cuz I wanted to know like compared to other devices u use how bad is it. Afaik the xperia z also has same heating up problems. Perhaps too powerful of a cpu lol. A good way to combat it is undervolting. Not sure if available for s4 d or not

No underclocking is underclocking. Dont underclock cuz I believe our devices need the power. But I find often that the voltage being supplied to the proc is unnecesarrily high. So I undervolt a lil. Once I undervolt my devices run much much cooler. I find this especially true for samsung devices. Surfing generally produces a lot of heat cuz the processor seems to be chugging and eating up juice. So I slow down its juice intake.

Iphones seem to be more efficient processor wise when surfing. Thats why if iphone and like a flagship samsung device go head to head battery test both pure surfing, they actually last similarly. Because iphone dont eat that much juice while samsung eats a lot. But if a mix of uses then iphone would lose. Also I do get iphone heating up when I play extensive gaming. Surfing yea not so much. Its processor.

I dont think its much to worry about.

I recommend
1. Underclocking (I dont)
2. Undervolting (I do)
3. Both (youll see epic battery savings too)

The s4 has a lot of stuff running in background also. Nfc. That eye scanning thingy. Smart stay. Whatever stuff. If u dun use I recommend switching off. Also as usual make sure u close unused apps properly. And off gps if not using too.

Take a look at "BetterBatteryStats" - https://play.google.com/store/apps/details?...terbatterystats

For underclocking and undervolting recommend setcpu. On playstore. However the ability to do noth would depend on whether u are rooted and whether your kernel supports it. If it does u will wanna tread carefully as it can cause your device to crash and the only way to fix would be a factory reset. Uncle benny can shed more light on how much u can reduce the voltage to a minimum of 800mv. I generally reduce all by 75mv for my note 2 to a minimum of 800mv (or if by default already lower I dont touch)

I recommend system tuner proby this developer called 3C since its one of the few system apps still being updated. Setcpu havent updated in a long while.

Use your own thread please. We cannit advise we dont own the device. But usb memang cant charge well. Depends on the pc. Maybe wire problem but doubtful. Thats it.