Undervolted 8550U in HP X360
 
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Undervolted 8550U in HP X360  

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ha1o2surfer
(@se12897)
Trusted Member
Joined: 3 years ago
 

Hello all, I recently got my hands on an X360. The 8th Gen Model with the 8550U. I have been undervolting to get better performance as I sold my 13R3 by Alienware since this CPU paired with a 1070 is more powerful. So I got my CPU to score 9500 in Passmark benchmarks but I achieved this by undervolting very aggressively. Look below.

https://imgur.com/ndKEfVB

This has tested Stable and I keep edging it lower as I played some Overwatch for 3 hours and no crashes, Lots of Intel Burn in test, no crashes. Temps under full load are 65c and it can hit 30watts turbo for about 3 minutes then it must be hard locked to drop down to 15. But once it idles again, it can jump right back up to 30 watts. This yeilds better performance than my 7700HQ...

Is this really for real? lol

Here is the passmark result

https://imgur.com/ySZpC78

2018 13" HP Spectre X360 [8th,4C,U] + GTX 1070 @ 32Gbps-TB3 (Sonnet Breakaway 550) + Win10 [build link]  

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kingmetal
(@kingmetal)
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Joined: 2 years ago
 

Wow, this is really interesting! I'm just getting into undervolting my X360, but you seem to have a much more sophisticated handle on it. I have a bunch of questions!

I was under the impression that keeping the cache and the core voltage offsets the same was a requirement, but your results say otherwise.
I'm also really curious if undervolting the GPU helped much.
What are the system agent and analog I/O?? That's a big undervolt on those components!
What kind of sustained turbo clocks are you seeing with that setup?

I've actually been running a -0.80mv undervolt on my machine for the last day and it APPEARS stable, but given your settings I'm wondering if I haven't given it enough of a thrashing. Played Far Cry 5 for several hours without issue, system was unstable above -0.85mv. I'm using XTU rather than throttlestop and setting the Core / Cache voltages to the same value.

This is very exciting!

EDIT: WOW I misread your core voltage offset and didn't realize how extreme yours is. You either won the silicon lottery or I'm doing something very wrong! That's incredible, that's probably a significant boost in performance given the TDP limits HP has imposed.

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kingmetal
(@kingmetal)
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Joined: 2 years ago
 

So far I'm not able to hit anywhere near your CPU core undervolt, I've managed to get it semi-stable around -0.090mv with values between 80-90 on the system agent, analog i/o and cache. Any tips? Do you start with a single value and find the limit then move on to the next or do you just have to sort of feel your way through them all in concert? Whats your process like?

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ha1o2surfer
(@se12897)
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Joined: 3 years ago
 

I have heard about the cache/core voltages needing to be the same. To be honest, I don't know much more than that and I also figured it was just for the desktop 8th gens/ being only useful for overclocking. lol So I need to do more research on that for sure. If those voltages were not setting I wouldn't be getting the same readings in XTU so I know the voltages are true and given what XTU says, I am really undervolting almost .5v under the specs. It's almost unreal but heres how I got there. It's actually very simple. 

Undervolting a CPU usually results in issues cropping up randomly. I set an easy .100 offset and run intel burn in test for 10 minutes. If it doesn't crash, great, set the cache voltage to also .1 offset. keep going from there. The good thing about using throttle stop is I set it on boot when I find a good setting. XTU can do that via powershell but it's unreliable in my findings. Throttle stop works even waking up from sleep where as XTU resets stuff. Idk I just don't like XTU at all. The Intel GPU is very sensitive to voltage offsets. so use XTU for benchmarking (yeah I know I said I don't like it but it's an easy way to bench the iGPU) the iGPU and set it to .80 offset and be done with it. I've seen the CPU turbo off and cause the display to act funny when the iGPU is just idle. It's very weird. The Analog I/O... lol no idea what that is. I have seen an idle crash though if the Analog I/O is set too aggressively, same goes for the system agent, I get crashes a lot when using my thunderbolt dock if I set a crazy offset for system agent. Just my findings.. take that for what it's worth lol. I use AIDA 64 for the cache stress test since I can't get a -2 offset to crash in windows but it does crash in a benchmark. 

TLDR; set each voltage range separately, find the stable voltage and move on to the next.. CPU, GPU, Cache and so on. I can bet almost every CPu can at least have an offset set to .080 at least.

2018 13" HP Spectre X360 [8th,4C,U] + GTX 1070 @ 32Gbps-TB3 (Sonnet Breakaway 550) + Win10 [build link]  

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ha1o2surfer
(@se12897)
Trusted Member
Joined: 3 years ago
 

Update, I have my undervolt even lower now. 

undervolt
2018 13" HP Spectre X360 [8th,4C,U] + GTX 1070 @ 32Gbps-TB3 (Sonnet Breakaway 550) + Win10 [build link]  

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kingmetal
(@kingmetal)
Active Member
Joined: 2 years ago
 

I'm in awe of your undervolt. That's a golden chip right there! You said it best: unreal!!

Congratulations. I'd love to know what kind of sustained long-term turbo your chip can hit with all cores loaded. CPU intense games like Far Cry 5 push mine to around 2.6ghz sustained, which I'm honestly really impressed with, but my undervolt isn't nearly as extreme as yours. I bet you're closer to 3Ghz!

I've been having what I think are iGPU related BSODs with my undervolt so I need to tune it a lot more, but I suspect I've got a relatively normal chip and won't be able to get much over .08mv, which is honestly still a pretty nice boost in performance.

EDIT: Any other tips? What Windows power profile are you using?

My research has indicated that older Intel CPUs needed the CPU Core / Cache to match voltages but the 8th gens do not, so that explains that. I've also not been able to find anyone who can confirm that Analog I/O and System Agent have any effect on performance, but perhaps that's not the case and you've stumbled onto more 8th gen magic. These are early days, so there are a lot of exciting possibilities. Almost makes me want to repaste mine! Almost...

Thanks for sharing, please keep it up!

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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febel26
(@febel26)
New Member
Joined: 2 years ago
 

I just got a HP Spectre X360 13" with i7 8550U and started experimenting with undervolting to get the most out of it. I use ThrottleStop to lower the core voltage, do a quick test in "TS bench" and then use Prime95 to stress test. I'm a little confused though as I was able to dial very low offset voltages without being able to make it crash (I've gone as far as -0.75V with others at the same values as SE12897) The best TS bench score I got so far was 10.1 (lower is better right?) but if I keep lowering the offset voltage it gets worse, maybe that's because the starting temperature is always higher, but I feel I might be doing something wrong... And I did turn on ThrottleStop... My Cinebench score is at 623 IIRC

Thanks

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(@eduardo_pinto)
New Member
Joined: 2 years ago
 
Posted by: SE12897

Hello all, I recently got my hands on an X360. The 8th Gen Model with the 8550U. I have been undervolting to get better performance as I sold my 13R3 by Alienware since this CPU paired with a 1070 is more powerful. So I got my CPU to score 9500 in Passmark benchmarks but I achieved this by undervolting very aggressively. Look below.

https://imgur.com/ndKEfVB

This has tested Stable and I keep edging it lower as I played some Overwatch for 3 hours and no crashes, Lots of Intel Burn in test, no crashes. Temps under full load are 65c and it can hit 30watts turbo for about 3 minutes then it must be hard locked to drop down to 15. But once it idles again, it can jump right back up to 30 watts. This yeilds better performance than my 7700HQ...

Is this really for real? lol

Here is the passmark result

https://imgur.com/ySZpC78

Hi, thanks for sharing your results!
As a newcomer to the undervolting scene and also owning a x360 8550U, I would like to know if you could spare a bit of your time and make kind of a guide to undervolt our similar machines and get a bit better results, although I can imagine not all of us can achieve the same as you have 😛

btw some other modifications worth doing, repasting with better thermal paste and nvme upgrade to a 970. although opening this machine and working inside requires steady hands and a lot of screws.... at some point I was afraid i would only screw things up :O

Cheers!

Thank you!

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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nonferrous
(@nonferrous)
New Member
Joined: 2 years ago
 
Posted by: Eduardo Pinto
Posted by: SE12897

Hello all, I recently got my hands on an X360. The 8th Gen Model with the 8550U. I have been undervolting to get better performance as I sold my 13R3 by Alienware since this CPU paired with a 1070 is more powerful. So I got my CPU to score 9500 in Passmark benchmarks but I achieved this by undervolting very aggressively. Look below.

https://imgur.com/ndKEfVB

This has tested Stable and I keep edging it lower as I played some Overwatch for 3 hours and no crashes, Lots of Intel Burn in test, no crashes. Temps under full load are 65c and it can hit 30watts turbo for about 3 minutes then it must be hard locked to drop down to 15. But once it idles again, it can jump right back up to 30 watts. This yeilds better performance than my 7700HQ...

Is this really for real? lol

Here is the passmark result

https://imgur.com/ySZpC78

Hi, thanks for sharing your results!
As a newcomer to the undervolting scene and also owning a x360 8550U, I would like to know if you could spare a bit of your time and make kind of a guide to undervolt our similar machines and get a bit better results, although I can imagine not all of us can achieve the same as you have 😛

btw some other modifications worth doing, repasting with better thermal paste and nvme upgrade to a 970. although opening this machine and working inside requires steady hands and a lot of screws.... at some point I was afraid i would only screw things up :O

Cheers!

Thank you!

Yes I am a new comer to this too and would love some step by step guidance on your underclocking process.

I have an Elitebook x360 1030 G3

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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Izaac
(@izaac)
Active Member
Joined: 2 years ago
 

What program are you using to undervolt your Spectre? 

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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