i7-6700T vs i7-6700 - lowest possible power consumption

[rsjo]

I'm looking at building a system that has a ~200 TDP and as part of this i am struggling to figure out if i can / should go with a i7-6700 over the i7-6700T model.
Adding the non T model would mean an additional 35W TDP and that would go beyond 200 TDP based on this calculation: http://outervision.com/b/l3ieVF

So my question is if a i7-6700T model running at full turbo (3.6ghz) will consume more or less power than an i7-6700 running at base clock 3.4Ghz with undervolting?
Ideally im looking for whatever model that can get me as close as possible to ~3.5Ghz with the lowest possible TDP.

My understanding is that undervolting should lower overall TDP but it's not guaranteed how much a given CPU can be undervolted?

The reason for the 200 TDP target is due to my wish of running this with an PicoPSU 160-XT which peaks at 200W while being able to build an overall system capable of running model titles such as GoW4, Tomb Raider, Hitman etc. at 1080p@60FPS as well as using this system for Dolphin emulation which will push at least 2 cores to maximum utilisation.

Thank you in advance - this is my first ever custom build so any additional insights from people who have tried to accomplish this before is much appreciated.

 

[AtenRa]

What case do you want to use for this build ??? im asking because of the Pico 160W PSU

 

[rsjo]

What case do you want to use for this build ??? im asking because of the Pico 160W PSU

The S4 Mini by NFC Systems - http://nfc-systems.com/s4-mini/

 

[coercitiv]

The reason for the 200 TDP target is due to my wish of running this with an PicoPSU 160-XT which peaks at 200W while being able to build an overall system capable of running model titles such as GoW4, Tomb Raider, Hitman etc. at 1080p@60FPS as well as using this system for Dolphin emulation which will push at least 2 cores to maximum utilisation.

Thank you in advance - this is my first ever custom build so any additional insights from people who have tried to accomplish this before is much appreciated.

I strongly suggest you thoroughly read the PicoPSU manual and specs before choosing components.

The 12V rail has a max load current of 8A and a peak load of 15A, so afaik that means this PSU can handle up to 180W for short periods of time and only 100W for continuous load on the 12V rail. On top of that active cooling is required under such loads, and a poorly ventilated enclosure requires even lower power usage:

At max load, forced air ventilation is required. For fanless or improper ventilation operation de-rate the output of the 3.3 and 5V rails until PSU temperature falls below 65C. Peak load should not exceed 60 seconds. Combined max power output should not exceed more than 200watts.

Unless you plan to underclock and undervolt the heck out of the i7 and the GTX 1060, your hardly stand a chance to keep this system under 100W on the 12V rail. It would take an i7 brought down to 35W - like it's mobile counterpart - and a GTX 1060 kept @ 1500Mhz to accomplish that.

Having said that, I would still go for the stock i7 6700, limit top frequency around 3.5Ghz, enforce a power limit either through BIOS or software. Depending on how lucky you get from the CPU lottery, you might even be able to clock the CPU higher and use the power limit to make sure everything is in order while the chip clocks as high as it can for the current load. This will help you squeeze all performance for the emulation software.

 

[AtenRa]

Ok nice, are you going to use a dGPU as well and if yes which one ??

 

[rsjo]

Ok nice, are you going to use a dGPU as well and if yes which one ??

I was looking at http://www.gigabyte.com/products/product-page.aspx?pid=5986#kf kept at @1500MHz as i have seen other S4 Mini builds based on this type of setup.

This is basically what i am after: https://smallformfactor.net/forum/threads/nfc-s4-mini-85-desert-night-6700t-gtx-1060-sc.942/
However as i am intending to use this with the Dolphin emulator i need as high a clock as i can get which comes back to my initial question on if i can keep the non-T model of i7-6700 at ~35W or if i would be better off with the i7-6700T.

 

[rsjo]

I strongly suggest you thoroughly read the PicoPSU manual and specs before choosing components.

The 12V rail has a max load current of 8A and a peak load of 15A, so afaik that means this PSU can handle up to 180W for short periods of time and only 100W for continuous load on the 12V rail. On top of that active cooling is required under such loads, and a poorly ventilated enclosure requires even lower power usage:

Unless you plan to underclock and undervolt the heck out of the i7 and the GTX 1060, your hardly stand a chance to keep this system under 100W on the 12V rail. It would take an i7 brought down to 35W - like it's mobile counterpart - and a GTX 1060 kept @ 1500Mhz to accomplish that.

Having said that, I would still go for the stock i7 6700, limit top frequency around 3.5Ghz, enforce a power limit either through BIOS or software. Depending on how lucky you get from the CPU lottery, you might even be able to clock the CPU higher and use the power limit to make sure everything is in order while the chip clocks as high as it can for the current load. This will help you squeeze all performance for the emulation software.

So essentially with the i7-6700 i *should* be able to get close to 35W given my luck in the CPU lottery?
What i dont understand is if the i7-6700T model with a 35TDP target will go above that when running at 3.6Ghz turbo boost or if that TDP is based on the base clock purely?

Ideally i would buy both CPUs and test but there is a cost associated with that

 

[AtenRa]

I was looking at http://www.gigabyte.com/products/product-page.aspx?pid=5986#kf kept at @1500MHz as i have seen other S4 Mini builds based on this type of setup.

This is basically what i am after: https://smallformfactor.net/forum/threads/nfc-s4-mini-85-desert-night-6700t-gtx-1060-sc.942/
However as i am intending to use this with the Dolphin emulator i need as high a clock as i can get which comes back to my initial question on if i can keep the non-T model of i7-6700 at ~35W or if i would be better off with the i7-6700T.

First of all as coercitiv said, the Pico PSU will not do for both the CPU and dGPU. You will have to get what they used

• HDPLEX 250w DC-DC PSU + DA330PM111
  

 

[rsjo]

The build i link to is using the PicoPCU-160-XT and their recordings in terms of power consumption are functional and stable at 160-180watt.
But i understand that what you are stating is that i am in peak territory with this type of setup so the HDPLEX @250W would be the better / right option here?

Based on the PicoPSU manual coercitiv send those recommendations in terms of peak and power usage are only marked for 5v and 3.3v where as the 12v notes a sustained peak of 12v 15amps = 180w with the total draw not going above 200w.
i guess i will be pulling most of the wattage from the 12v rail?

 

[AtenRa]

The 35W TDP CPU will throttle down earlier but will reach the maximum clocks, having a 65W TDP CPU undervolted will only bring down the power consumption. I really dont know if the 65W TDP CPU will be able to maintain the higher clocks when undervolted operating in that SFF case. So even if the CPU has 4GHz single core at 65W TDP it may never reach that frequency if undervolted and operating at this environment.

It may be better to wait until January for KabyLake 35W TDP Core i7, it should be able to maintain higher clocks at lower TDPs than Skylake.

 

[LTC8K6]

There is a 25W TDP 4C/8T Skylake Xeon, so I guess there just wasn't a market for a desktop low TDP version.

http://ark.intel.com/products/88169/Intel-Xeon-Processor-E3-1240L-v5-8M-Cache-2_10-GHz

Unless you go with a mini server board?

http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&IsNodeId=1&N=100007629 600009028 601186375

 

[coercitiv]

So essentially with the i7-6700 i *should* be able to get close to 35W given my luck in the CPU lottery?
What i dont understand is if the i7-6700T model with a 35TDP target will go above that when running at 3.6Ghz turbo boost or if that TDP is based on the base clock purely?

Ideally i would buy both CPUs and test but there is a cost associated with that

TDP is not maximum power consumption. Even if you buy the 6700T, if you want to make sure the CPU does not burst beyond 35W you still need to limit max power usage. You can do that through a number of ways, using either BIOS or software running at OS level, although it wouldn't be necessary.

The only advantage the 6700T brings is it's already configured for 35W TDP, while the 6700 would require a bit of BIOS tinkering (and availability of certain BIOS settings that influence max power draw). The 6700 on the other side will allow for more flexibility, especially maximizing clocks when only 1-2 threads are running.

If you choose the 6700, make sure your motherboard BIOS exposes max power settings.

The build i link to is using the PicoPCU-160-XT and their recordings in terms of power consumption are functional and stable at 160-180watt.
But i understand that what you are stating is that i am in peak territory with this type of setup so the HDPLEX @250W would be the better / right option here?

Based on the PicoPSU manual coercitiv send those recommendations in terms of peak and power usage are only marked for 5v and 3.3v where as the 12v notes a sustained peak of 12v 15amps = 180w with the total draw not going above 200w.
i guess i will be pulling most of the wattage from the 12v rail?

Manufacturer defines peak power usage as max power usage for periods of time no longer than 60 seconds. Thus, peak power is not a value you can use for continuous usage.

Both CPU and GPU will draw power from the 12V rail. This means your budget for both CPU and GPU power is only ~100W, at least that's what I can gather from manufacturer info. (max current 8A x 12V = 96W)

The 35W TDP CPU will throttle down earlier but will reach the maximum clocks, having a 65W TDP CPU undervolted will only bring down the power consumption. I really dont know if the 65W TDP CPU will be able to maintain the higher clocks when undervolted operating in that SFF case. So even if the CPU has 4GHz single core at 65W TDP it may never reach that frequency if undervolted and operating at this environment.

If his mobo BIOS exposes power usage settings such as Max Short/Long Power Usage Limit or Max Current Limit, then he can configure the processor to clock as high as possible within the given power envelope. The CPU will certainly reach 4Ghz in some low threaded cases (light laods), and sustained clocks will improve with undervolting.

However, there's no guarantee clocks will be equal or higher than on 6700T, especially on well threaded apps. On low threaded apps there might be some extra performance to squeeze out.

To give the OP an idea on what happens in the 3500Mhz territory, my 6600K @ 3400 Mhz uses around 40-45W while running Prime 95 Blend test at stock voltage (4Ghz power usage is 60-65W). If I limit Prime 95 load to 2 threads, power usage drops to 30W @ 3400Mhz or 40-45W at 4Ghz. So if I were to enforce a 35W power limit and run a 2 threaded emulation software, my stock i5 would clock higher than 3.5Ghz.

 

[rsjo]

I was thinking about using this mobo: http://www.gigabyte.com/products/product-page.aspx?pid=5901#ov but this is purely based in that i have seen other people use this in these types of builds.
In the manual it states that Power Limit TDP (Watts) / Power Limit Time and Core Current Limit (Amps) can be set and controlled.

In terms of how the CPU behaves with load on 2 vs 4 cores as an example, will it automatically control this and make a 2 threaded app (Dolphin) automatically perform better or would i have to configure that in BIOS / Software before i launch Dolphin?
In your example with the 35W power limit and a 2 threaded emulation software - would that just happen automatically when the system only sees load on 2 cores?

I will go with the i7-6700 and see if i can figure out how to configure these settings to hit ~35W.

Thank you very much for your assistance and i might re visit this thread once the kit arrives if i have any issues with the actual configuration.

Have a great day!

 

[coercitiv]

In terms of how the CPU behaves with load on 2 vs 4 cores as an example, will it automatically control this and make a 2 threaded app (Dolphin) automatically perform better or would i have to configure that in BIOS / Software before i launch Dolphin?
In your example with the 35W power limit and a 2 threaded emulation software - would that just happen automatically when the system only sees load on 2 cores?

The whole idea behind setting a power limit instead of a max clock limit is to not worry about the number of threads - the CPU clocks as high as it can in the circumstances.

I will go with the i7-6700 and see if i can figure out how to configure these settings to hit ~35W.

I took a look in the manual of the Gigabyte board, it only seems to have settings for Turbo mode (short term), not for base long term power usage as well. I'm not 100% confident it will allow you to set power limits bellow stock TDP. My Z170 board has separate settings for Turbo and Long Term power draw. If you can, ask owners of the Gigabyte board to check how that setting behaves.

I just put a 35W limit on my 6600k via BIOS, undervolted by 70mV, left CPU multiplier at 40x, then booted and rand Prime 95 Blend test with different thread counts:
1 thread - 4Ghz
2 threads - CPU jumps between 3.6 - 3.9 Ghz (let's say 3.8Ghz average)
4 threads - jumps between 3.2 - 3.5 Ghz

Up to 4 threaded usage you can feel confident this is what you're likely to see at 35W with a bit of undervolting. Keep in mind the clocks above are for Prime 95, not typical gaming loads which are lighter. Games that use more than 4 threads will bring clocks lower, but that hardly matters since overall performance will be higher on well threaded games anyway.

 

[Glo.]

Even tho 6700 has 65W TDP it can consume over 80W under load.

6700T and other "T" series are Power Gated CPUs. However the 6700T can consume up to 40W of power under load.

I am in similar situation to you. I am currently building a low-power/high-performance computer, and decided to go with completely new build for 1080p FreeSync gaming.

i7 6700T, Asus Z170l Pro Gaming Motherboard, Samsung 960 Evo 250 GB, XFX Radeon RX 470, SilentiumPC Vero 600W, Cryorig C1, Fractal Design Nano-S case, WD Red 2 TB HDD, Corsair Vengance LPX 2400 MHz

In my office my friend and I built two computers that have been differing just by the GPUs. XFX RX 470, and MSI GTX 1050 Ti.

Power consumption tests at the wall, while gaming. Non VSynced: Overwatch for GTX 1050 Ti - 145W at the wall. RX 470 - 218W.

Vsynced is where it gets interesting: Overwatch for GTX 1050 Ti - 135W of power at the wall average power consumption. RX 470 - 138-140W at the wall in the same game. We tested 1080p and Epic Settings.

Non Vsynced scores for Overwatch: MSI GTX 1050 Ti - 65-68 FPS, RX 470 - 92-94 FPS. Both were 4 GB models.

Why we compared the two GPUs? Because the price difference is 120 PLN in my country between those two GPUs.

There is not huge difference in performance between i7 6700T and 6700. But there will be huge difference in power consumption between the two CPUs.

If you want high performance CPU with low power, go with i5-6600K. It consumes non-OC'ed around 65W, and has very high core clocks. And is cheaper than i7 6700T.

 

[AtenRa]

If his mobo BIOS exposes power usage settings such as Max Short/Long Power Usage Limit or Max Current Limit, then he can configure the processor to clock as high as possible within the given power envelope. The CPU will certainly reach 4Ghz in some low threaded cases (light laods), and sustained clocks will improve with undervolting.

Definitely, if his Mobo allows him to set the TDP at 35W then 6700 is better than the T variant.
I would say 6700K could be even better if the BIOS allows for single Core OC.
OC single Core to 4.4GHz, set TDP to 35W and downvolt until Single Core is stable at 4.4GHz. Best case scenario i suppose.

 

[rsjo]

My Z170 board has separate settings for Turbo and Long Term power draw. If you can, ask owners of the Gigabyte board to check how that setting behaves.

What vendor and model is your board?
I have looked at both Gigabyte and ASUS mini-itx offerings but they both seem to only offer control of short term power usage and not long term (base) as you also stated.

 

[coercitiv]

What vendor and model is your board?
I have looked at both Gigabyte and ASUS mini-itx offerings but they both seem to only offer control of short term power usage and not long term (base) as you also stated.

Mine is Z170I Gaming Pro AC, however I should mention I really bought it due to a combination of low availability of mITX boards and a big discount at the time of purchase. I cannot recommend it over other models as I simply took a plunge and bought it based on specs, layout and a few reviews.

 

[dave_the_nerd]

Sounds like you need a 1050 instead.