Help Me understand the FX-8300
Help Me understand the FX-8300
Hello guys
I own a Phenom II 955 for four years and recently upgraded to the FX 8300. It’s tough to overclock the 955, but this one behaves very differently. I’m not an overclocker and I’m worried about temperatures going above 50 degrees.
After about 20 minutes under load, the average values stay almost the same.
My CPU is the M5A78LMUSB3 with four phases and no heatsink, and I have a Hyper TX3 in the CPU. I haven’t explained my airflow configuration, but I’ve tried a lot and got the most balanced results possible.
I have CPU overvoltage set to 1.30v in BIOS and 60% loadline calibration, which helps reduce voltage spikes, especially under load. CnQ, Turbo is off, and C6 is enabled.
I’m confused about the low power setting, given the 900Mhz clock. Also, I’ve seen Turbo applying around 1.40–1.50v to reach 4.2GHz manually, but all clocks stay perfectly stable at 1.28v.
So, is the FX 8300 really flexible and not demanding? Did I get a particularly good batch, or is my board pretending it can handle it but it’s not?
I had a 6300, so my remarks mostly come from my personal experience with that model, though they should be relevant to the 8300 I imagine, since they’re essentially the same early Vishera Silicon.
I could easily push mine overclocked to 4.4Ghz; I’d aim for 4.5Ghz. However, in my situation it was mainly the VRM of my motherboard (M5A88M) that limited me; 4.4 was the optimal point for reaching P95 'til sunrise. But without heatsinks, the FETs would overheat at 4.5 and begin throttling during small FFTs, even with a fan running.
Additionally, with only one LLC setting enabled, I had to set Vcore at 1.45. Otherwise, voltage fluctuations could damage cores until they cooled again.
I was also using a TX3 which wasn’t sufficient for a 6300—even a Hyper 212 wouldn’t fit my case. A 4.2Ghz clock would be a minor improvement for these chips; you should aim for 4.6–4.7Ghz as a high-side target if your motherboard has a robust VRM with plenty of phase-count and proper cooling. A good Noctua cooler or at least a 240mm AIO would be ideal.
With that configuration, my CPU temperatures stayed between 55–60°C (only during Prime95), which I thought was high, though I now understand that some users pushed it close to the 70°C shutdown limit and voltage up to 1.55 bit-mining for extended periods at 4.8–5Ghz.
What matters most is how you overclock your 955: I have one at 3.9G and am hesitant to increase further. It’s stable, but the FETs keep overheating and throttling if I don’t add a fan. My son already has his 6300 overclocked to 4.4 with much lower voltage on a ga-990fxa-ud3.
EDIT update...just noticed! You’re using an M5a78 board. If that’s correct, it shares the same VRM section as my M5a88. Perhaps a better BIOS and VRM tuning, especially for LLC, would help—but it won’t be enough. I can’t see it sustaining an 8-core FX at 4.5Ghz in P95 small FFTs. It will throttle severely.
If you’re serious about pushing the limits, investing in Enzotech heatsinks to secure the FETs would be wise:
https://www.amazon.com/Enzotech-Mosfet-P...B004CLDIHK
and then adding a fan to direct airflow to that area. You’re much more likely to damage a FET than your CPU when testing for P95 stability.
Based on your observations, I've been conducting additional tests. I achieved very stable voltage and clockspeed at 4.0ghz. This leads me to consider that the 955 might be around 3.4 and occasionally it triggers random instability or boot loops. Additionally, it was showing full TDP under heavy load, which is another point I'm trying to understand. With VRMs touched, it causes discomfort but doesn't damage my fingers.
Taking into account your observations, I’ve continued testing. I achieved very stable voltage and clock speeds at 4.0ghz. This led me to wonder if the 955 could drop to 3.4 and occasionally trigger random instability or boot loops. Additionally, it was showing full TDP under heavy load, which is another point I’m puzzled about—especially since I adjusted the VRMs, but my finger still feels okay despite the heat.
It’s possible your 8300 is throttling because APM remains enabled. Checking the CPU Core Multiplier in HWInfo might help: if it falls from 21 (assuming a 200Mhz FSB at 4.2Ghz) to a much lower number during a P95 run, that could indicate throttling. Core loading percentages likely won’t decrease significantly since the cores are still active but running at a reduced frequency.
My M5a88 didn’t have a BIOS option to disable APM on FX processors, so it would automatically throttle to stay within TDP limits. If you can’t find a BIOS setting in your M5a78, try searching online for a command-line tool named 'AMD MSR Tweaker'. It’s a specialized utility that might help. Running it as an admin in Command Prompt could disable APM on FX processors. If the system ever goes into sleep mode, it should restart with APM enabled again.
With APM turned off, the throttling would likely come from the VRMs. You can set up a batch file to run as a startup job in Windows 10, but make sure to execute it with admin privileges. I only used it occasionally—mainly when encoding videos, so it helped keep things running smoothly. Navigating through Windows, browsing the web while using Word or Excel, or playing games rarely kept all cores at full capacity; usually, just one or two cores operated near their maximum, not even close to 100%. Even with 4.4Ghz, only a few cores could finish tasks quickly before power limits caused throttling.
Good luck!