I executed Prime95 for 5 hours on a non-OC Haswell i7 4790K.
I executed Prime95 for 5 hours on a non-OC Haswell i7 4790K.
Seems a bit high too me, for not being overclocked. My 6700k overclocked to 4.5Ghz full time hits just about those same numbers. Your ALL core turbo speed, even running Prime, can't be 4.5Ghz on all cores so your thermals should be a bit better but are certainly within tolerance. There is room for cooling improvement but you are unlikely to see anything close to that in normal use, even gaming or running most applications.
Darkbreeze :
It feels a bit too high for me since I haven’t been overclocked. My 6700k was boosted to 4.5Ghz all the time, and it still reaches similar results. Your full-core turbo speed, even when Prime is on, can’t sustain 4.5Ghz across all cores, so your cooling should be okay but might need a bit more improvement. There’s potential for better heat management, but you probably won’t notice much difference in regular use, not even during games or heavy tasks.
Do you know what might be behind the temperature rise? I just added a Corsair H115i AIO.
The outside temperature was around 27 degrees Celsius.
Could it be related to the CPU block placement or the thermal paste contact? If not, what else could be contributing to the heat increase for my non-OC i7 4790k?
Thanks again!
Typically, the issue arises from slight imperfections in how the backplate is fastened to the standoff screws. Motherboards vary in thickness, so cheaper models tend to be thinner than premium ones. This can lead to inconsistencies in tightening the assembly with the same fasteners. It’s not always a matter of insufficient tightness; sometimes it’s just that you didn’t tighten enough, but avoid over-tightening to prevent damage.
Adding a small plastic washer between all four holes where the bolts pass through the backing plate and the backside of the motherboard helps shift the backing plate slightly away from the board. This prevents the standoff-to-bolt distance from reaching its limit, solving the problem.
In simpler terms, these spacers (tiny plastic washers) between the backing plate and the motherboard ensure the entire assembly is securely fastened to the hardware side. Without them, fasteners might not be fully seated, causing looseness when connecting the water block to the top of the standoff. This can result in insufficient pressure between the CPU lid and the water block/cold plate.
If you need clarity, I can provide an image or diagram to illustrate this.
Darkbreeze usually explains this issue by pointing out that the slight misalignment in fastening the backplate to the standoff screws is common. Motherboards vary in thickness, so cheaper boards tend to be thinner than premium ones, which can affect how securely identical fasteners fit together. This isn’t always the main cause—sometimes it’s just not tight enough—but avoid over-tightening to prevent damage.
Using a small plastic washer between all four holes where the bolts pass through the backing plate and the backside of the motherboard helps shift the backing plate slightly away from the board. This prevents the standoff-to-bolt distance from reaching its limit, solving the problem.
In short, spacers (tiny plastic washers) between the backing plate and motherboard ensure a flat, secure fit. Cleaning the CPU lid and cold plate with isopropyl alcohol and reapplying paste may also help.
If you need further clarification, an image or diagram would be useful.
I understand if this isn’t clear—I can provide more details or visuals.
Thank you!
EDIT: But why remove the CPU lid? I usually just clean the thermal paste in place. Should I always take it off?
Also, as another user said, if your 4790K is on a z87 or z97 board it will turbo mode automatically so it can run up to 4.520. Does that mean it actually reaches 4.5 under load with my specific mobo?
Don't stress about Turbo mode. It's just how it works, meant to function that way. It's not an additional feature you need to add or expect. It's intended to occur naturally. If you can't accept this standard behavior, there may be other issues at play. Disabling Turbo is merely a temporary fix for something else that isn't working properly.
Manually adjusting the CPU speed is essentially bypassing the issue, which might not solve the underlying problem.
You don't literally remove the CPU cover when turning it off. When you take out the cooler, you clean the top surface of the CPU to eliminate the thermal paste from earlier installation. Reusing the same thermal paste isn't recommended because it can lead to issues like air bubbles and uneven coverage. Using old paste can cause further complications.
Darkbreeze:
You don't have to stress about Turbo mode. It's just how it should behave, built in for normal operation. It's not something you need to add or expect. It's meant to function as intended. If you can't accept that standard behavior, there might be other issues at play. Turning off Turbo is only a temporary fix for something else that isn't working properly.
Manual CPU throttling is essentially avoiding the real problem instead of solving it.
You don't literally remove the CPU lid. When you take off the cooler, you clean the top surface to eliminate thermal paste from the previous installation. Reusing the same paste isn't recommended—thermal paste must be cleaned off both the CPU and the bottom of the cooler where it touches the CPU. Otherwise, air bubbles will form and coverage will be poor, leading to further issues.
If you've reused the same thermal paste after removing the cooler before, that's likely the cause.
Hi again, darkbreeze,
I haven't reused the thermal paste, but I did apply a fresh one today while reseating the CPU cooler.
The issue is that my temperatures have kept rising. Within minutes they hit 70°C+ with Prime 95 26.6 Small FTTs.
Also, I switched to the ML140s fans from my stock H115i AIO model, which reportedly offers similar performance without the noise.
I also inspected the backplate and standoffs—everything seems securely fastened, with no play. No signs of loose components.
Any suggestions? Could it be that the CPU is simply old?
How much thermal paste are you using and EXACTLY what method are you using to apply it? Using too little or too much thermal interface material can definitely cause poor temps just the same as having poor mounting pressure can.
Also, please outline the exact configuration of your entire cooling system. How many fans. Where every fan is located and in what direction the airflow of that fan is actually moving air is.
Check the manufacturer product page for bios updates. Update to any version that is prior to December 2017. Do not install any version that is newer than that, as it is probably related to the recent Spectre and Meltdown vulnerabilities and likely has been recalled due to faulty, error riddled microcode. Prior to December though is fine and might result in changes to the stock voltage behavior of the default CPU management profile.
Check the bios to see what the vCore CPU voltage is set to.
Also check the RAM speed and voltage settings. Report both of those back here.
Being an "old" CPU is unlikely to have anything to do with it. CPUs can run and run and run, for years and years. They don't usually just suddenly start getting warmer because they've grown long gray beards and are using a cane to hobble along.
Darkbreeze asks for details on the amount of thermal paste used and the precise application technique. He notes that insufficient or excessive paste can lead to temperature issues, similar to inadequate mounting pressure. He requests a full overview of the cooling system setup, including fan placement and airflow direction. He also wants to verify the BIOS version, specifically checking for updates before December 2017 due to known vulnerabilities. Additionally, he asks about CPU voltage, RAM speed, and voltage settings, requesting these details be provided.
Yeah, break in is for thermals to hopefully get BETTER, not GOOD. Should be GOOD from the start if everything is right and there are no issues.
Break in isn’t your problem.
What BIOS version do you have installed?
What is the idle temperature of your CPU after five minutes of inactivity, once Windows has loaded up the desktop?
And again after five minutes of running Small FFT?