Question the newest CPU with cTDP feature in latest AMD and Intel processors - to build a fanless server

Apr 30, 2020
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dear community

i am very very glad to be here in this great commuity - i really like TomsHardware - is great and this communit is much much more than expected : i really like the ideas & knowldge-sharing in this forum here. all things regarding Hardware and many many other topics can be discussed here so greatly and supportive.

And today i have a special question . one that may find some here that can also share ideas and experience. so i post it in the hope that no admin or mod just thinks . wow - another off topic - lets erase it..
at th moment i look for the newest CPU with cTDP feature in latest AMD and Intel processors - to build a fanless server

i need some guidance and Build Help in Building a fanless/passively cooled web server

I am looking to replace older server HW: what I currently have running a server with a robust, full-featured option that can utilize faster data transfers on my local network, such as file and media sharing, while still allowing remote HTTP and FTP access (HTTP meaning that I will be hosting a website).
I am not gaming or anything with it, so graphics are unimportant to me for this build. If at all possible, I would like the build to be both small and energy efficient (I'm thinking something like a 35w TDP CPU, such as the i5-6600T) or - if there is a newer one then i would love to take a newer one so that I can leave it running 24/7 without worrying about the electric bill or noise.

In terms of budget, I am willing to spend around $1000. I already own plenty of storage drives, and I have a spare 250GB SSD

Currently, all i want to know which cpu i shoud take into consideration - any and all advices will be appreciated.

cTDP feature in latest AMD and Intel processors

Configurable TDP (cTDP) is a mechanism to change the standard TDP of a processor to a lower TDP that requires less power and cooling compared to the standard TDP. This is achieved by a lower core frequency and voltage. cTDP is a requirement if the cooling solution of the CPU is not suitable, e.g. very thin devices or when a quite mode is preferred over the maximum performance mode. AMD made this feature first available in selected models of the “Kaveri” based A-Series. Intel introduced this feature in the U/Y Series of ultra low power “Haswell” mobile and newer mobile “Broadwell” CPUs. The cTDP feature from Intel is controlled by the firmware/EC and is set by the device manufacturer and cannot be changed, AMDs implementation allows the user to set this feature on selected desktop models (Kaveri, Carizzo) when the required option is available in the firmware/BIOS. Mobile CPUs e.g. AMDs 2016 35W “Bristol Ridge” models have a cTDP range of 25-45W and
Intels 2016 “Skylake” top U-Line models have a base TDP of 28W and a lower cTDP from 23W to 22.5W (low power mode). The device manufacturer can set the value that fits the cooling solution in that device. In this case the setting is locked by the manufacturer and cannot be changed. The advantage is only one CPU for different thermal envelopes, but you have to check what cTDP is set to compare speed and battery life of the same CPU model.
look for recommmendations -
Currently, all i want to know which cpu i shoud take into consideration - any and all advices will be appreciated.
 
Just reduce the multiplier on your CPU of choice until it runs cool enough for your needs. I believe Asus' boards software even has some TDP targets pre-baked, but really that's all they're doing also. That's all any CPU is doing to hit a target TDP.

I capped my i7-3770 to run at 1.9GHz max when I'm folding and 4.2GHz when I'm gaming. Just a simple BIOS adjustment. Load whichever saved BIOS profile I need for that situation.
 
Reactions: matze
I capped my i7-3770 to run at 1.9GHz max when I'm folding and 4.2GHz when I'm gaming. Just a simple BIOS adjustment. Load whichever saved BIOS profile I need for that situation.
This can also be done from windows with the intel extreme tuning utility,I know that a lot of people like doing this from bios but for most people the ease of use is more important.
 
Reactions: matze
^very true. And all the big 4 (Asus, msi, gigabyte, asrock) have their own overclocking software as well that does the same thing.

I just don't like having background processes/ software running. It's a wierd OCD of mine.
 
Apr 30, 2020
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hello you both -- many thanks for the input and for sharing your thoughts and insights. This is great!


cTDP feature in latest AMD and Intel processors


https://www.anandtech.com/show/14664/testing-intel-ice-lake-10nm/5

Power Results (15W and 25W)
Based on the SKU table, Intel was very keen to point out that all of the Y-series processors for Ice Lake and all the 15W U-series processors have cTDP up modes. This means that OEMs, if they build for it, can take advantage of a higher base power of a processor which leads to longer turbo periods and a higher frequency during sustained performance levels.
While cTDP is a good idea, one of the issues we have with the concept is that Intel’s OEM partners that design the laptops and notebooks for these processors don’t ever advertise or publicise if they’re using a CPU in cTDP up or down mode. I could understand why a vendor might not want to advertise using a down mode, but an up mode means extra performance, and it’s hard to tell from the outside what is going on.
For what it is worth, most users cannot change between these modes anyway. They are baked into the firmware and the operating system. However there are a few systems that do expose this to the user, as I recently found out with my Whiskey Lake-U platform, where the OS power plan has advanced options to set the TDP levels. Very interesting indeed.

[...]....

Also, that third test – if you are wondering why that graph looks a little light on the data points compared to the others, it is because the AVX-512 instructions took so much of the time on the CPU, that our power software didn’t get any for itself to update the power values. We still got enough to make a graph, but that just goes to show what hammering the CPU can do.

For the base power consumption, we actually have an issue here with the observer effect. Our polling software is polling too often and spiking up the power a little bit. However, if we take the average power consumption between 25-30 seconds, under 25W this is 2.96W, and under 15W this is 2.87W, which is similar.

For users interested in the score differential between the two:

For 3DPM without AVX instructions, the 15W mode scored 816, and 25W mode scored 1020 (+25%).
For 3DPM with AVX-512, the 15W mode scored 7204, and 25W mode scored 9242 (+28%).
 
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TDP is given on the "base clock" of a CPU. If you look closely, you'll see that CPUs (in the same family and process node) will have lower TDP value if their base clock is lower.

https://www.anandtech.com/show/13544/why-intel-processors-draw-more-power-than-expected-tdp-turbo

You can adjust both the base clock on a CPU as well as the boost clock AND the "Tau" (time limit the CPU can be at the turbo boost frequency). These things are all adjustable in your aftermarket mobo (Asus, AsRock, MSI, Gigabyte) BIOS.
 

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