My new graphics card is acting weird?

[Otocumbia]

Hello, this last week I bought a new graphics card, a RX-560 with 4gb.
My PC has 8gb DDR3 RAM and a A10 7870k processor that comes with a R7 integrated graphics.
The theme is that I bought the 560 to improve my experience, but something really weird happened.
After I done everything, I started my gta v, the first time, it was at like 60 fps with high graphics, great. The second time I open it, it was like 20, when I low the graphics... IT'S THE SAME, so I reached the conclusion that something weird was happening to my videocard, taking in account that my previous integrated video card ran gta v at 30 fps more or less. Now sometimes I play it at 60 or 20 fps, no idea at all.
Then, I tried with Minecraft... 30 FPS, 30, no shaders and same results with high and low graphics. 
I even checked my core and gpu temperature, I saw that my CPU was at 80°C that is pretty hot, but after a search, I saw that even if my processor or graphics card are hot, it shouldn't affect the performance.
Other thing that I thought could be a bottleneck, but, do you think that my processor could be making bottleneck to my GPU in MINECRAFT??? 

Today I woke up and new problem, for some reason, my PC now starts, but my screen doesn't even show anything now..
To conclude, I bought a graphics card to play games like gta v at a reasonable speed and now Minecraft runs at 30 fps with no apparent reason, any suggestions? Thanks in advance...

[RozRocks]

You're being bottle necked by the CPU. Both of the games you mentioned are very CPU intensive. To get better performance, you need a more powerful CPU

[BHJohnson]

The A10 APU's were designed to roughly pair with R7 graphics, as indicated by including R7 GPU's as their onboard chips. I ran one in CrossFire with an R7 dedicated card for a while, just to try it. You've got about two generations of gap between your processor and your graphics card, and the processor is a pretty mediocre processor even within it's own generation. Additionally, 80C is getting into thermal throttling range, but I'm not sure when that starts to happen on that chipset since I never ran one that hot. Your processor isn't just bottlenecking your GPU, it's straight up choking it out with a submission hold. I ran some benchmarks on my old A10 system with an R7 of some flavor, and the two were almost perfectly matched.

 

Get a stock AIO cooler from an FX 8150 if you can find a place to put it (it fits FM2 sockets) and use that to cool the APU. That should make for a more consistent experience. Then work on saving up to get either an AM3+ board with an FX CPU in it for cheap off eBay or Amazon, or just upgrade to a cheap AM4 board with a Ryzen 3 or 5. The AM4 option will require new RAM in addition to the CPU and mobo, so that's something to figure into the cost.

 

Also, Minecraft can be a pretty CPU intensive game depending on the world you are playing in and what mods are installed. I crashed an overclocked FX 8150 just from making a cobblestone generator. Good times.