F5F Stay Refreshed Power Users Overclocking Does using a small FFT version of Prime 95 that supports AVX help figure out if the 9900k overclocking is stable?

Does using a small FFT version of Prime 95 that supports AVX help figure out if the 9900k overclocking is stable?

Does using a small FFT version of Prime 95 that supports AVX help figure out if the 9900k overclocking is stable?

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SnoopMKWii
Junior Member
19
04-02-2026, 07:37 PM
#1
I've heard that this test makes too much work for the CPU and isn't really good for a 9900K. But there seems to be some arguing about it still. My custom overclocks pass for 8 hours in both Realbench (with half RAM turned off and no WHEA errors) and Prime95 Blend with AVX disabled, plus 4 hours in Memtest and 2 hours in Aida64 FPU stress, along with another 2 hours of Prime95 small FFTs also with AVX disabled. Is this enough to say it's fine?
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SnoopMKWii
04-02-2026, 07:37 PM #1

I've heard that this test makes too much work for the CPU and isn't really good for a 9900K. But there seems to be some arguing about it still. My custom overclocks pass for 8 hours in both Realbench (with half RAM turned off and no WHEA errors) and Prime95 Blend with AVX disabled, plus 4 hours in Memtest and 2 hours in Aida64 FPU stress, along with another 2 hours of Prime95 small FFTs also with AVX disabled. Is this enough to say it's fine?

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_lomtel_
Junior Member
3
04-11-2026, 07:25 PM
#2
Your numbers are mostly right, but sometimes things change depending on the CPU or how you tweak it.
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_lomtel_
04-11-2026, 07:25 PM #2

Your numbers are mostly right, but sometimes things change depending on the CPU or how you tweak it.

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josiecatz__10
Senior Member
640
04-12-2026, 03:28 AM
#3
Using Prime95's small FFTs with the AVX feature keeps your CPU cooler from overheating. Running Asus Realbench for eight hours or doing a Cinebench R20 loop makes sure your voltage stays stable. If both tests pass without any problems, then you are good to go.
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josiecatz__10
04-12-2026, 03:28 AM #3

Using Prime95's small FFTs with the AVX feature keeps your CPU cooler from overheating. Running Asus Realbench for eight hours or doing a Cinebench R20 loop makes sure your voltage stays stable. If both tests pass without any problems, then you are good to go.

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guestman25
Junior Member
44
04-17-2026, 09:03 PM
#4
Got the info. I'll try to do some work on the P95 tomorrow.
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guestman25
04-17-2026, 09:03 PM #4

Got the info. I'll try to do some work on the P95 tomorrow.

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David_Martial
Member
231
04-17-2026, 11:43 PM
#5
Be careful because running P95 with AVX can be tough for some coolers, so turn off AVX for your first few test runs.
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David_Martial
04-17-2026, 11:43 PM #5

Be careful because running P95 with AVX can be tough for some coolers, so turn off AVX for your first few test runs.

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Ion23
Member
170
04-22-2026, 07:00 AM
#6
I ran my tests without AVX for about fifteen minutes and got up to seventy-four degrees Celsius. Those numbers are already quite hot.
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Ion23
04-22-2026, 07:00 AM #6

I ran my tests without AVX for about fifteen minutes and got up to seventy-four degrees Celsius. Those numbers are already quite hot.

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EmmyG123
Member
142
04-26-2026, 05:16 AM
#7
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EmmyG123
04-26-2026, 05:16 AM #7

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RottiePvP
Member
180
04-27-2026, 12:59 PM
#8
It stopped working right away when I turned on the 5GHz mode and used all cores overclocked. I was pretty nervous about that. Now I switched back to 4.9 GHz, which is why I'm hopeful it might work again today. 😊
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RottiePvP
04-27-2026, 12:59 PM #8

It stopped working right away when I turned on the 5GHz mode and used all cores overclocked. I was pretty nervous about that. Now I switched back to 4.9 GHz, which is why I'm hopeful it might work again today. 😊

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Senshi_
Member
197
05-04-2026, 02:47 AM
#9
AVX is an extra feature that works with x86 processors. It does 256-bit floating point math. AVX2 adds support for doing 256-bit integer work. AVX-512 changes the speed from using two separate blocks to a single block of 512 bits on both floats and integers. This new version is supported on just a few specific chips, like the Intel Core i9-9900K. Running Prime95 with small FFT tests shows up as 100% real-world load. AVX, AVX2, and AVX-512 are very strong on CPU usage and heat generation. This causes the CPU to work harder than a normal synthetic test would suggest. Some games use a little bit of AVX for things like physics in explosions or rock chunks, but I don't think any game uses AVX2 or AVX-512. That kind of power is mostly used by big companies making software and engineering tools. For a regular gaming PC owner, it's probably pointless because you won't really see that much power when playing games anyway. You might lose out on some of those extra instructions if they're not needed. If you want to test your system, sure, but turn AVX2 and AVX-512 off at least before starting.
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Senshi_
05-04-2026, 02:47 AM #9

AVX is an extra feature that works with x86 processors. It does 256-bit floating point math. AVX2 adds support for doing 256-bit integer work. AVX-512 changes the speed from using two separate blocks to a single block of 512 bits on both floats and integers. This new version is supported on just a few specific chips, like the Intel Core i9-9900K. Running Prime95 with small FFT tests shows up as 100% real-world load. AVX, AVX2, and AVX-512 are very strong on CPU usage and heat generation. This causes the CPU to work harder than a normal synthetic test would suggest. Some games use a little bit of AVX for things like physics in explosions or rock chunks, but I don't think any game uses AVX2 or AVX-512. That kind of power is mostly used by big companies making software and engineering tools. For a regular gaming PC owner, it's probably pointless because you won't really see that much power when playing games anyway. You might lose out on some of those extra instructions if they're not needed. If you want to test your system, sure, but turn AVX2 and AVX-512 off at least before starting.

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chrisjo785
Member
196
05-04-2026, 03:33 AM
#10
Thanks for getting back to me. Yeah, I'm trying really hard but nothing is working with my 4.9GHz all-core overclock. The computer keeps freezing or showing BSODs. I don't think the heat is the problem since the temps are already way too high (around 80c), so I didn't try turning up the voltage to 1.3v because that feels like a lot for this chip. Even when running tests at P95, the voltage drops down to 1.145v. That's the lowest I've ever seen on these test boards. I'm pretty sure that's already my limit.

I don't want to try pushing the voltage higher or start messing around with the LLC again since I don't have time. Besides all the testing I've already done, what else should I run to prove it works? I really don't want to send this ship out on a boat until I'm 100% sure it's stable.
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chrisjo785
05-04-2026, 03:33 AM #10

Thanks for getting back to me. Yeah, I'm trying really hard but nothing is working with my 4.9GHz all-core overclock. The computer keeps freezing or showing BSODs. I don't think the heat is the problem since the temps are already way too high (around 80c), so I didn't try turning up the voltage to 1.3v because that feels like a lot for this chip. Even when running tests at P95, the voltage drops down to 1.145v. That's the lowest I've ever seen on these test boards. I'm pretty sure that's already my limit.

I don't want to try pushing the voltage higher or start messing around with the LLC again since I don't have time. Besides all the testing I've already done, what else should I run to prove it works? I really don't want to send this ship out on a boat until I'm 100% sure it's stable.

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