CPU Undervolt 8th gen non k intel CPU?

TutenStain

Case Bender
Original poster
Feb 12, 2018
2
0
Hello,
I am building a new SFF computer and need to keep the temperatures down. I am thinking of getting an entry level 6 core Intel 8400. However, to shave off a few deg my plan was/is to underclock/undervolt it. Is this possible with non k processors? Will I have any way of actually lowering the voltage/speed or do I need to upgrade to 8600k which comes at a higher TDP but then undervolt that instead? Or would it maybe even be possible to just lock a 8400 at non turbo speeds and in thay way limit the power usage?

Thanks.
 

ignsvn

By Toutatis!
Moderator
Apr 4, 2016
1,423
1,259
I turned off Turbo Boost on my i5-4670 (an 84 Watt chip), limiting it to its original top speed at 3.4 Ghz (Turbo will bring it to 3.8 Ghz)

I got like 6-8 C temperature decrease.
 

rcodi

SFF Gamer
Aug 5, 2017
140
107
AFAIK underclocking is not possible on non-K but undervolting is and should be possible on most popular boards. I've undervolted both the 8400 and 8700 successfully on an Asus Z370.
 

bichael

Average Stuffer
Dec 17, 2017
58
49
Will depend a bit on the motherboard but I think most non Z boards would allow an undervolt of a non K chip and some adjustment of clock speed, for sure at least turning the turbo off.
I have a 4790 with turbo locked to max on all cores and with a significant undervolt (1.03V) using a B85 board.
I've just picked up a B150 board (with an i5 6500) and the manual suggests voltage control and some control over multiplier (maybe just turbo) is possible. There's even a power saving mode which it suggests will lower vcore and vccin.
 
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bichael

Average Stuffer
Dec 17, 2017
58
49
Just to note that seems I was wrong above... with Skylake I have no real control other than turning turbo on/off with my i5 6500 and B150i. The bios allows turbo ratio adjustment (so I tried locking all cores at max turbo) and allows voltage adjustment (so I tried adding -ve offset) but both seem to have zero effect. Even the power saving mode which suggests it will adjust vcore doesn't do anything. A bit disappointing compared with Haswell. Can't be sure if the limit is the non-k cpu or the non-z board, but given the options are there in the bios maybe it's the cpu?
On the plus side the out of the box power use does seem like it's still noticeably lower than I had with my undervolted Haswell and cooling is just not an issue at all.

edit - Seems I am able to undervolt using Intel XTU. So good news but still confused why the bios can't then do it.
 
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