Hello all!

Would anyone know if there's any heat sink capable of passively cooling 25-35 watt CPUs?

I have a very small form factor case case, permitting a heatsink height of about 50mm (around 53mm or so). I was looking at coolers such as the Scythe Kozuti or the Prolimatech Samuel 17. Unfortunately, my current cooler is not fully capable of handling the 4765T without the fan. It only works with a really, really aggressive underclock (down to 1000 MHz and the GPT down to 800 MHz).

Thanks for reading!

Case - Realan E-K3i mITX
Power Supply - 120 watt PicoPSU
Motherboard - MSI Z87i mITX
Processor - Core i7-4765T 25 watt (35 w/turbo)
RAM - Crucial Ballistix low-profile low watt, 16GB
Hard Drive - OCZ Vector 256GB
Operating System - Windows 8

Well the NoFan CR-95C Copper Fanless CPU Cooler probably can, but im guessing you want on the small factor for your small case, i dont think there is one. You could move into something like HDPLEX H3.SODD Fanless Mini-ITX HTPC Case that should allow you to passively cool the with the case itself.

I would just get a Scythe Kouzuti (40mm height with fan), just in the US is more expensive now since most 3rd party sellers are from japan. Or a Noctua NH-L9I (37mm with fan height), just as expensive as scythe.

Welcome to SPCR.

There may not be enough mass to conduct the heat away in these tiny coolers to run passive. The good news is the Scythe Kozuti was only 12 dBA in SPCR testing with a 95W TDP CPU at 65C. Your CPU should be a piece of cake.

Thanks for the welcome! Great forum, by the way.

I believe you. What gets me is that on 10 watt Atom CPUs, they have these tiny passive coolers. I theorized that on a 25 watt (or 20 watts underclocked down to around 1600 MHz) CPU, I'd only need about twice the metal in the Atom heatsink. Unfortunately, it appears that I may need about four times that. There's probably some element that I'm not accounting for. This is really confusing, though. It would seem that underclocking does not reduce power consumption in as dramatic a fashion as one might imagine.

I'm starting to lean toward the Kozuti - thanks for the suggestion!






Those are super awesome! HDPLEX is a bit large for my needs, unfortunately. I'm trying for the VESA mountable build, rather than the set top box. But that would definitely be my first choice for a home media center.

I've been trying to get back in contact with a German seller of a case called Star Metronic. They're not yet ready to sell in the states, although the owner briefly offered to sell to me before they went public. Unfortunately, I have not yet heard back from him, but it was the perfect case. So close! Hopefully he gets back to me.

There was also the Nimbus, but they're not yet ready to sell in the states, either. All the best stuff is Austrian, German or Japanese.

Power is proportional to V^2 * f,

where:
V is the core voltage
f is the frequency.

So, underclocking should linearly reduce the CPU power, while undervolting is a power-of-2 effect. See if your mobo allows a negative offset in the core voltage. A 0.1V drop on a 1.08V load leads to a ~18% power drop.

Regarding the cooler, it's more than just mass. The size of the die, it's heat density, the attachment method to the IHS, all come into play.

Thanks! Offset doesn't appear to be available in my UEFI. I saw a number of settings pertaining to voltage reduction, but "offset" is the only term I'm familiar with that relates to undervolting.

I know the UEFI settings vary by board, but I couldn't find a good definition for VCCIN

VCCIN and CPU Core Voltage are the only two elements that I can change. Core voltage can only adjust upward of its initial value. It also has three settings - auto, override and adaptive. Adaptive lets the voltage automatically adjust... I think this has something to do with the baked-in voltage regulator inside of Haswell.

VCCIN, which I'm not familiar with, adjusts all over the place. Its default is around 1.8v but it can adjust much further down than that. Perhaps I can adjust VCCIN?

Nothing new to advise here, but to confirm that compared to fanless, a small amount of forced airflow is more convenient & practical, cheaper, smaller, and ultimately, no different in perceived noise level. The mentioned Scythe Kozuti, with fan set to low speed (under say 1700~1800rpm), is likely to cool your CPU better yet be virtually as silent as any fanless heatsink you can fit into the kind of case you desire. VESA mounting on the back of a monitor will further isolate the fan noise from you.

An even smaller alternative to the Kozuti is the Noctua NH-L9i, which isn't quite as effective but nearly as quiet, and virtually guaranteed to fit on any mini-itx board & case.

What a shame. Maybe an MSI mobo owner will pipe up and comment on how/if you can undervolt this mobo. (It's not VCCin).

I should probably post a separate comment about that. Thanks for the idea!

I've read in a German forum that suggests voltage offset does exist in a beta of the firmware for this board.

I've heard that Haswell's "adaptive" voltage management setting does much of the job of undervolting - it automatically adjusts and shifts around voltage, instead of being constant. Perhaps I misunderstood them, and unfortunately didn't check to see if my board would undervolt before purchasing. Fortunately, it looks like Asrock makes a z87 mITX board that can undervolt.

However, there's been some VERY early reports that undervolting does make a big difference in Haswell, so apparently adaptive voltage management isn't all it's cracked up to be?



I may go with the Noctua as it's easier to find and slightly cheaper. Per your suggestion, I'm thinking of just going with low air flow and underclocking.

It's a shame that those GE Piezo fans, ionic or Sandia. coolers turned out to be vaporware. I suspect some company bought the patent and then scrapped it.