Consider whether further boosting your Vcore is advisable for your i7-8700K at 4.7GHz.
Consider whether further boosting your Vcore is advisable for your i7-8700K at 4.7GHz.
The overclocking manual only mentions Prime95 v26.6 Small FFT for valid reasons. Are you sure you aren't referencing a newer release like 29.4? The differences in core voltage, temperatures, and stability are significant.
How effectively you can handle an 8700K depends largely on securing a quality chip.
As of 3/22/2018
The percentage of I7-8700k chips that can operate at an aggressive vcore around 1.4 or higher with delidded 4.9 99%
5.0 88%, 5.1 54%, 5.2 22%
Be aware of the delidded warning to maintain temperature control.
Your NH-D15s provides excellent cooling, so heat issues should be manageable.
If you keep improving and bring the vcore down to about 1.3 or lower, everything should work well.
1.4v is often recommended as a tough limit; I believe the Intel maximum is 1.5v.
I wouldn’t push beyond that.
During stress tests, keep an eye on the vcore using cpu-Z.
Also, apply speedstep and adaptive voltage to lower the multiplier and vcore when the CPU is idle.
Once you reach your limit, reduce the multiplier slightly.
How much of that final multiplier is really necessary?
Although it's accurate that each chip's overclocking capacity varies slightly because of manufacturing flaws and imperfections, this still doesn't feel correct to me.
For a 4.7 ghz boost on the i7 8700k, using 1.3V for Vcore, it remains unstable even after a short prime test. Hmm, I think there might be another factor at play here.
Usually, all 8700k models should easily reach 5.0 ghz without issues.
... unless you encounter an extremely defective chip.
The overclocking manual only mentions Prime95 v26.6 Small FFT for valid reasons. Are you sure you aren't referencing a newer release like 29.4? The differences in core voltage, temperatures, and stability are significant.
Thank you all for your helpful responses!
Following geofelt's suggestion, I adjusted my Vcore to 1.32V and finally achieved stability during the prime-testing phase!
CompuTronix provided the correct explanation.
I actually used the most recent prime95 release instead of the older version—v26.6. When testing with v26.6, it remained stable at 1.24V.
😉
Your insights are really appreciated.
Still, I’m a bit confused about this situation (and that’s why I skipped downloading the exact version mentioned in the guide). If the goal of the stress test in OC is to verify CPU stability under any load, shouldn’t it be capable of running any stress test, even the latest prime95?
Is my OC stable if I know it works with v26.6 but not with v29.4?
... I opted for the most recent iteration of prime95 rather than v26.6. And let's see what happens when I try v26.6—stable at 1.24V... Shouldn't it handle any stress test, even with the newest prime95?... In reality, my OC remains stable if I can confirm it works with prime95 v26.6, but not with v29.4? mysterry, The key distinction lies in a significant factor named "AVX" (Advanced Vector Extensions), which greatly influences processor heat output. Version 26.6 isn't AVX-enabled, whereas newer releases do support it, leading to substantial processor strain near 130%. This demand is extremely demanding and far surpasses typical usage or other applications. Even though the maximum temperature listed for the 8700K is 100°C, maintaining a cooler core is essential for optimal stability, performance, and lifespan. Therefore, it's wise to maintain a comfortable thermal buffer below the maximum threshold. The standard operating range for core temperatures is as follows: Core temps exceeding 85°C aren't advisable. Temperatures under 80°C are preferred. These readings are sensitive to surrounding conditions, so unless you have a consistent indoor climate (around 22°C or 72°F), temperature swings can lead to dangerously high core temperatures during warmer periods. Not all tasks are equal. Stress tests fall into two types: - Stability tests with changing workloads - Thermal tests with constant loads Intel evaluates processors under full 100% power consumption to confirm thermal specs. Prime95 version 26.6 Small FFTs is perfect for CPU thermal evaluation because it maintains a steady workload, keeping core temperatures close to the manufacturer's specifications. It closely mimics Intel's actual testing conditions. Other tools that either overload or underutilize the processor won't provide accurate thermal data. Here’s a breakdown of utilities categorized by thermal and stability tests based on their TDP share, averaged across six generations at default settings (rounded to 5%): All results display 100% CPU utilization in Windows Task Manager, reflecting resource usage rather than actual power draw. Core temperatures are directly tied to heat generation (Watts), which depends on the workload. Prime95 v26.6 Small FFTs delivers a consistent 100% load, ensuring core temps stay within acceptable limits for most CPUs, especially those with Hyperthreading like the 8700K. These tools closely replicate Intel's testing environment. Utilities that avoid overloading or underloading your processor will offer reliable thermal benchmarks. Below is a comparison of tools sorted by thermal and stability categories based on TDP percentage, averaged across six generations at standard settings (rounded to the nearest 5%): Every test indicates full CPU usage in Task Manager, which shows processor activity, not power consumption. Core temperatures adjust according to heat output, which is dictated by the workload. Prime95 v26.6 Small FFTs maintains a stable 100% load, meaning your processor should handle demanding real-world tasks without overheating. 4th through 9th generation i9, i7, i5, and i3 CPUs support AVX instruction sets. Versions of prime95 after 26.6 utilize AVX on the CPU's floating-point unit, creating an unrealistic workload that can raise core temperatures by up to 20°C. Many 6th through 9th generation motherboards mitigate AVX issues via BIOS "offset" adjustments (downclocking) at 300 MHz or higher. If you avoid AVX-intensive applications like rendering or transcoding, stability isn't the only concern—BIOS settings should still be optimized for such tasks. Prime95 should work well even without AVX support. AVX can be turned off in later prime95 versions by adding "CpuSupportsAVX=0" to the local.txt file. However, since core temperatures remain similar to 26.6, it's simpler to stick with the original version. According to Intel’s specifications, TDP and thermal performance are confirmed without AVX support. To better understand this, refer to: Intel Temperature Guide -