CPU Question about CPU TDP and long term power usage considerations.

JosephEK

Cable-Tie Ninja
Original poster
Mar 6, 2017
175
84
I was looking at the Coffee Lake CPU lineup on Wikipedia
https://en.wikipedia.org/wiki/Coffee_Lake

and I notice there's a CPU like the i5 8400 with 6c,6t that can turbo up to 4.0 on 1 core and 3.8 on all cores.

then I see a T series processor i7 8700T with 6c,12t that can also turbo up to 4.0 on one core and 3.8 on all 6. And it has faster clocked iGPU ontop of that.

Does advertised TDP not count for when a CPU is turbo-ing? Or are the T series CPUs binned for higher efficiency?

Only reason I ask is for potential future build. A CPU like the i5 8400 is 100 USD cheaper, but when I take into account the death of Moores law and the fact that I'm still using my i5 3450 6 years later without much issue (a CPU that the i5 8400 / i7 8700T would completely destroy) I have to assume that this next system could be in service for well over a decade and that long-term power consumption may play more role in CPU choice than ever before.

And then there's underclocking, but I don't know how to do that or if it's even possible on locked CPUs or if it would achieve the same performance/watt as one of these T series models.

Another consideration is Ryzen APU. Vega 11 absolutaly crushes UHD 630, but 4 cores is so boring in 2018. I have to wonder if Zen 2 APUs on 7nm will see any 6 core APU parts.
 
Last edited:

tinyitx

Shrink Ray Wielder
Jan 25, 2018
2,279
2,338
Intel's TDP definition:-
''Thermal Design Power (TDP) represents the average power, in watts, the processor dissipates when operating at Base Frequency with all cores active under an Intel-defined, high-complexity workload. Refer to Datasheet for thermal solution requirements.''

BTW, when you said you want to consider ''long-term power consumption'', do you mean the utility bill?
I am curious, have you roughly estimated/calculated how much you can save between a 65W and a 35W CPU, over a time span of 10 years?
 

Duality92

Airflow Optimizer
Apr 12, 2018
307
330
For me, at $0.1$/kWh saving 30w for 10 years would equate to 0.03*0.1*365*10 which is $10.95. That's if it's at load 100% for 10 years. We can easily assume at idle, which it might spend 18+ hours a day doing, we remove 75% of that and it becomes like $2.74 for 10 years, or rather a quarter a year. (this is in CAD too, but I don't know how much electricity cost where you are)
 

JosephEK

Cable-Tie Ninja
Original poster
Mar 6, 2017
175
84
BTW, when you said you want to consider ''long-term power consumption'', do you mean the utility bill?
I am curious, have you roughly estimated/calculated how much you can save between a 65W and a 35W CPU, over a time span of 10 years?
Yeah utility bills. It's my mom who actually pays the electricity bill she earns a lot more than I do which is why I consider reducing expenses very seriously for when she's not here anymore. Hell I even hang-dry my own laundry. The hope that a DIY a day keeps the capitalism away is what it is I guess.

The best tool I've found so far for determining cost of running a CPU is this thing on PassMark:
https://www.cpubenchmark.net/compare/Intel-Core-i7-8700T-vs-Intel-Core-i5-8400/3213vs3097

I just use a national average of ~.12 USD / Kilowatt hour, then because I run my PC almost all the time except when I shut it down to go to work or out of the house (It's my Gaming system, TV and sleep aid all in one) I estimate it runs atleast 16 hours a day. I honestly couldn't tell you average utilization because it must vary when I'm playing games which include Minecraft, Rocket League and various shooters.
 

Duality92

Airflow Optimizer
Apr 12, 2018
307
330
I gave you for formula of the added costs, IF it was running pegged on a benchmark for 24 hours a day, it'd be like a dollar a year.

You're gonna save more by turning off your room lights.
 
  • Like
Reactions: JosephEK and Gautam

JosephEK

Cable-Tie Ninja
Original poster
Mar 6, 2017
175
84
I gave you for formula of the added costs, IF it was running pegged on a benchmark for 24 hours a day, it'd be like a dollar a year.

You're gonna save more by turning off your room lights.
Cool. Didn't see your post until after I wrote that first reply earlier and it refreshed when I submitted. I doubt that considering my room light is just a 9w LED that sees far less use than my PC.
 

n13L5

Trash Compacter
Aug 20, 2017
51
10
For me, at $0.1$/kWh saving 30w for 10 years would equate to 0.03*0.1*365*10 which is $10.95. That's if it's at load 100% for 10 years. We can easily assume at idle, which it might spend 18+ hours a day doing, we remove 75% of that and it becomes like $2.74 for 10 years, or rather a quarter a year. (this is in CAD too, but I don't know how much electricity cost where you are)

Just think what you could do with all those quarters provided you own a slingshot...
Invaluable!
 

tinyitx

Shrink Ray Wielder
Jan 25, 2018
2,279
2,338
Continue to hang dry your laundry.

Dryer costs a shitload to run.
Maybe diy a duct from the PC to the dryer and use the hot air exhaust to dry the clothes and save some money.
Or, just use those hot exhaust directly to the laundry. :D
 
  • Like
Reactions: n13L5