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Ways to reduce TDP of a non-lower power Core i5 CPU ?

A

ahmadka

Senior member
Hi guys .. So I'm build a HTPC, for which its generally recommended to have a CPU with a TDP <65W. So to fulfill this, I can of course get any i3 CPU, but I want an i5 instead. Problem is, in my locality the low power S and T CPUs are not available, so I'm wondering if there are any effective ways to manually lower TDP to under 65W ?

One way may be to underclock, but I don't know how successful this would be, and what motherboard capabilities will this require.

Second way might be to use a software like ThrottleStop, but again I don't know how effective/permanent such a solution will be as I'm never used such software before.

So basically I'm looking for some suggestions I guess.
 
AFAIK, throttle stop is to increase performance, not decrease power usage.

Try undervolting and matching the config with low voltage and frequency RAM. SSDs will help too if youre wanting a cool, quiet and power efficient setup.
 
Lots of chips will undervolt quite decently if you're over overclocking.

You'd be surprised how much more you can undervolt if you pull a few bins from the max speed.

Get something to plug in that will tell you how many watts your PC is using and keep in mind that if you run something like Prime 95 your CPU isn't going to be using nearly as much as that just doing normal PC things 🙂
 
ahmadka said:
One way may be to underclock, but I don't know how successful this would be, and what motherboard capabilities will this require.

Second way might be to use a software like ThrottleStop, but again I don't know how effective/permanent such a solution will be as I'm never used such software before.
Click to expand...
You can use Intel XTU: it's easy to use and should allow you to set the desired value for Max Turbo Boost TDP (effectively setting your custom TDP value for the CPU). With a bit of patience and testing you can also underlock/undevolt slightly to make it more efficient.
 
ahmadka said:
Hi guys .. So I'm build a HTPC, for which its generally recommended to have a CPU with a TDP <65W. So to fulfill this, I can of course get any i3 CPU, but I want an i5 instead. Problem is, in my locality the low power S and T CPUs are not available, so I'm wondering if there are any effective ways to manually lower TDP to under 65W ?
Click to expand...
The easy way:-

Go into Control Panel -> Power Options -> Balanced -> Change Plan Settings -> Change Advanced Power Settings -> Processor Power Management -> Maximum Processor State from 100% to 90%.

This effectively tells Windows to use the second highest Speedstep setting as the maximum load state (should be around 3.0GHz - the same base clock as an i5-4590S). No extra software needed or need to reboot. Doing it this way disables your Turbo Boost but that's not really an issue in a HTPC. It also works on non-Z motherboards which may not allow you custom multiplier / undervolting control in the BIOS.

If it's any use, testing on my "77w" i5-3570 the "percentage steps" are as follows:-

5% = 1.6GHz @ 0.680v (approx 24w)
65% = 2.2GHz @ 0.728v
80% = 2.6GHz @ 0.768v
90% = 3.0GHz @ 0.832v (approx 37w)
100% stock = 3.4GHz @ 0.888v (approx 48w)
100% + mild OC = 3.8GHz @ 0.976v (approx 54w)
100% + mild OC = 4.0GHz @ 1.005v (approx 59w)

Obviously each CPU is binned differently, other CPU's may have higher VID's, and my iGPU is disabled so you may need to add a few watts to above scores for that if you're not using a dGPU, but at 3GHz Speedstep state and a -0.15 to -0.2v lower voltage than stock 3.4-3.5GHz, you're virtually guaranteed to be well below the 65w TDP limit on any i5 with quite a bit of thermal headroom whilst effectively mimicking a base i5-4590S (without Turbo Boost).
 
Another suggestion, you may not need to change anything. If you are only using it for HTPC applications, an i5 will never run anywhere close to full load. TDP is only a max power rating that's used as a guideline for motherboard power delivery and cooler design. If you are just watching movies/online servies, etc, you will never get close to full load.
 
Undervolting is a good idea. If you have a lower binned chip that was likely created to just fill a segment and price, there's usually a ton of room to undervolt.

My old Q8200 would overclock from 2.33GHZ to 2.8GHZ while being able to undervolt from 1.4v to 1.05v. I assume the power consumption of that chip was amazing.
 
I have a 3470 in my HTPC - It's undervolted -0.050v could probably go more but I don't like it "in the red" in BIOS. It does make the temps drop a little and power consumption lower. This runs 50 watts idle and about 70 with the 5 disk RAID-5 array spun up.
 
elemein said:
AFAIK, throttle stop is to increase performance, not decrease power usage.
Click to expand...
I use ThrottleStop to decrease power usage on my laptop. You set a clock speed, not a power target, but it generally works. BSim500's idea might be easier to set up, though it does roughly the same thing.
 
On my desktop I keep my FX at 1400-2100mhz in CCC unless I'm gaming or doing serious work. It is silent and the CPU stays very cool.
 
If the board is relatively new and supports c-states, Intel Speedstep, etc. (see BIOS) which it should, power usage of newer Intel CPUs should not be an issue at all. At idle they're hardly using ANY power, Intel Speedstep etc. takes care of all that. (MAke sure to have in Power Options that the min. CPU usage is 5% and max. is 100%)

Also during watching movies it's unlikely that the CPU is maxed out so it's likely not using that max power either. Otherwise throttle stop and limit max. multi and possibly undervolt. But I really don't think it's needed. On the other hand, you likely don't even need Throttlestop either, just set max. CPU usage in power options, like, 70% or so....if the CPU goes even up that high for watching movies.
 
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