Having some problems with my FX-8300 and RX 570

[hi_feeeh]

I recently bought a RX 570, which for my FX-8300 is way overkill, I know.
So I tried running some games and, of course, some are literally unplayable, Rainbow Six, for example, even with the lowest graphics, the CPU keeps stuttering and when my CPU gets at 100%, my fps drops to 20 ~ 40 and it lags everything (that happens with the Ultra graphics too, it works fine until my CPU gets to 100% usage).
Now I tried overclocking my CPU to 4.2 GHz, but when it's at a heavy load, the voltage and the core just drops drastically (Frequency: 4200 MHz; VID: 1.1375V, when it drops: Frequency: 1400MHz; VID: 0.8375).
The weird thing is that all of that didn't happen when I had my old graphics card, which was a GTX 650 ti.
Now I just don't know what to do, since I'm new to overclocking, I may be doing something wrong and the clock just keeps going crazy because of that. I just don't know what else to do at this point and any help would be really great.
I just want to run my games.

Specs
MB: Asus M5A78L-M/USB3
CPU: AMD FX™-8300
RAM: 16GB DD3-1334
HDD: SAMSUNG HD103SJ
GPU: Asus Radeon Expedition RX 570 OC 4GB

 

[sizzling]

Your motherboard isn’t good enough for overclocking, it’s has weak VRM’s that are known to overheat. When the VRM’s overheat they throttle the cpu which is why the frequency and voltage drop drastically, it is the motherboard trying to protect itself.

A more powerful gpu tries to run higher FPS, the higher the FPS the more work the cpu has to do. You can either run the cpu at stock speed and live with the limited performance or upgrade to a modern platform which means new cpu/motherboard/RAM.

 

[Darkbreeze]

As mentioned:

Tier One: Fine quality. Good boards with fine enough thermals and power phases to contain FX 6, even OC it. Quality is decent for the price. Do NOT pair FX 8 with them, they may take the load of FX 8, but Power phases will not be good enough. No Crossfire/ SLI capability.


GA-78LMT-USB3
M5A78L-M/USB3 (See NOTE)

NOTE: M5A78L-M/USB3 does NOT have heatsinks on VRMs so don’t expect high OC on this board. It’s quite fine for stock speeds however.

Not only is that board not good enough to overclock on, it shouldn't even be USED AT ALL with an 8 core FX processor. Not even at the stock speeds. You had no problems before because you were not pushing the CPU anywhere near TDP, and now you are. Technically, a better board would be helpful, particularly one that you COULD overclock on, but the investment it would take to do that would put you up near what it would cost you to simply upgrade to a new motherboard, CPU and processor from the Ryzen lineup.

AM3+ boards of any decent quality at all, are very expensive now, and they are not worth the investment. Used ones are a waste of money because they are all rather old and have probably already seen the majority of the useful life of their capacitors go by. Undoubtedly there are probably a FEW decent deals out there on good AM3+ boards that people purchased shortly before Ryzen was released that they no longer need, but those will be few and far between and might still be rather too expensive to justify.

I would return your configuration to the stock not-overclocked configuration by resetting the bios or whatever you used to overclock such as AMD Overdrive, and live with it until you can afford to upgrade or replace the board.

I guarantee that your problem is related to VRM throttling on that board, with that CPU.