CPU coolers for LGA 1151: what fits a Skylake to Coffee Lake board
Almost any cooler whose box says LGA 115x or LGA 1200 bolts straight onto an LGA 1151 board, because all of those sockets share the same four-hole, 75 mm square mount. The real choice is heat and space. For a hot K chip such as the i7-8700K or i9-9900K in a normal mid tower, get the Thermalright Peerless Assassin 120 SE, a dual tower. If you want a single tower that keeps its fan away from your memory, the Noctua NH-U12S is the slimmer route. In a slim case with a 65 W or lower chip, the 37 mm Noctua NH-L9i is the one that closes the lid. A 65 W office box can get by with a compact 100 mm tower, covered below.
Why LGA 115x coolers fit LGA 1151
Intel's thermal and mechanical guide for LGA 1155 and LGA 1156 boards draws the four heatsink holes around the socket on a 75.00 mm square. Noctua's support pages say the heatsink mounting is identical on LGA 1150, 1151, 1155 and 1156, and that LGA 1200 kept the same mounting again. That is why makers lump the five sockets together as "115x" or "115X/1200" on their spec sheets.
What does not carry over:
- LGA 1700 and LGA 1851 use a 78 mm square and a different socket height. A cooler that lists only those sockets needs the maker's LGA 115x kit, if one exists.
- LGA 775, the socket behind our LGA 771 to 775 Xeon mod, has its own spacing. A few coolers carry both mounts.
One more trap concerns the board, not the cooler. Skylake (6th gen) and Kaby Lake (7th gen) chips run on 100 and 200 series chipsets; Coffee Lake (8th and 9th gen) needs a 300 series board. The socket looks the same either way. Before you plan a cooler around a chip upgrade, check that your motherboard supports the processor.
How much heat a 6th to 9th gen chip makes
Intel lists all of these as FCLGA1151 chips. Both the TDP and the cooler class Intel assigns come from its product pages.
| Chip | Generation | Cores / threads | Base / max turbo | TDP | Intel cooler class |
|---|---|---|---|---|---|
| Core i7-6700T | 6th | 4 / 8 | 2.80 / 3.60 GHz | 35 W | PCG 2015A (35W) |
| Pentium G4560 | 7th | 2 / 4 | 3.50 GHz | 54 W | PCG 2015C (65W) |
| Core i7-6700 | 6th | 4 / 8 | 3.40 / 4.00 GHz | 65 W | PCG 2015C (65W) |
| Core i3-8100 | 8th | 4 / 4 | 3.60 GHz, no turbo | 65 W | PCG 2015C (65W) |
| Core i5-8400 | 8th | 6 / 6 | 2.80 / 4.00 GHz | 65 W | PCG 2015C (65W) |
| Core i7-6700K | 6th | 4 / 8 | 4.00 / 4.20 GHz | 91 W | PCG 2015D (130W) |
| Core i7-7700K | 7th | 4 / 8 | 4.20 / 4.50 GHz | 91 W | PCG 2015D (130W) |
| Core i7-8700K | 8th | 6 / 12 | 3.70 / 4.70 GHz | 95 W | PCG 2015D (130W) |
| Core i7-9700K | 9th | 8 / 8 | 3.60 / 4.90 GHz | 95 W | PCG 2015D |
| Core i9-9900K | 9th | 8 / 16 | 3.60 / 5.00 GHz | 95 W | PCG 2015D |
| Core i9-9900KS | 9th | 8 / 16 | 4.00 / 5.00 GHz | 127 W | PCG 2015D |
Intel defines TDP as the average power at base frequency, with all cores busy on an Intel-chosen heavy workload. An i9-9900K running eight cores well above its 3.60 GHz base clock draws more than 95 W, and how much more depends on the power limits your board sets. Owners commonly report that enthusiast Z370 and Z390 boards set those limits high by default. Intel's own cooler class for the K chips, PCG 2015D, is labeled 130 W on its 6th to 8th gen pages.
A worked example. Say you have an i5-8400 on a 300 series board and want to drop in a used i7-8700K. The TDP goes from 65 W to 95 W, and Intel's cooler class goes from PCG 2015C (65W) to PCG 2015D (130W): double the design target. Our notes on sizing a cooler by TDP explain why watt ratings on cooler boxes are loose, and the cooler TDP headroom check turns your chip into a target figure.
Measure the case first
- Cooler height. Use the case maker's limit, or measure board surface to side panel and subtract a few millimeters.
- Memory. Note how tall your RAM is and how close the first slot sits to the socket. A tower's front fan is the usual collision.
- The back of the board. Backplate coolers need access behind the socket; no tray cutout means taking the board out.
- Airflow. Point a tower at the rear exhaust fan.
The picks
These picks come from makers' specifications and manuals, plus Intel's own documents, not from our own testing.
Thermalright Peerless Assassin 120 SE: for the hot K chips
The Peerless Assassin 120 SE is a dual tower: six 6 mm heat pipes rising from a nickel-plated copper base into two fin stacks, with two 120 mm fans. Thermalright lists the heatsink at 125 x 110 x 155 mm and 730 g, with each fan rated at up to 1550 rpm and 66.17 CFM. Intel support covers 115X, 1200, 1700 and 1851.
It suits the i7-8700K, i7-9700K and i9-9900K, whose real draw runs past their TDP. The trade-offs are size and weight. You need at least 155 mm of case height plus a margin, and Thermalright itself warns to leave clearance for tall memory. A 730 g heatsink with two fans is also a good reason to support the PC, or take the cooler off, before shipping it.
Noctua NH-U12S: the slim single tower
The NH-U12S is one tower with five 6 mm heat pipes and Noctua's NF-F12 120 mm fan, which tops out at 1500 rpm, or 1200 rpm with the supplied low-noise adaptor. Noctua lists it at 158 mm tall and 125 mm wide, but only 45 mm deep without the fan and 71 mm with it. That shallow stack helps keep the fan clear of the first memory slot. Noctua's socket list includes LGA 1151, 1150, 1155, 1156 and 1200 along with AM4, AM5, LGA 1700 and LGA 1851, and NT-H1 paste comes in the box.
It suits 65 W chips with plenty of margin and the 91 to 95 W K chips at sensible fan speeds. With less fin area than a dual tower, it will spin faster on a 9900K with wide-open power limits. Noctua supplies extra anti-vibration pads for adding a second NF-F12 in push-pull if you need more.
ARCTIC Freezer 7 X CO: the compact pick for office chips
For a 54 to 65 W chip in an older or smaller case, the ARCTIC Freezer 7 X CO is a compact tower: 132.5 mm tall, 425 g, two 6 mm heat pipes that touch the CPU directly, and one 100 mm fan on a dual ball bearing ("CO" stands for continuous operation). ARCTIC's spec sheet lists Intel 115x, 1200 and 775, plus AMD AM4, AM5, AM3(+) and FM1/2(+), with MX-2 paste pre-applied and no restriction on RAM height. It mounts on a frame that, by ARCTIC's account, goes on without removing the motherboard.
ARCTIC quotes a thermal resistance of 0.88 °C/W at 70 W, measured on an AMD Zen 2 chip on its own bench. Read literally, that is about 62 °C of rise at 70 W, which is fine for an i5-8400 and the wrong match for a 9900K. Its LGA 775 mount is a bonus if an old Core 2 board lives in your spares pile. ARCTIC's site now lists it under end of life, so stock may run out.
Noctua NH-L9i: for slim cases
The NH-L9i is a top-down cooler 37 mm tall with its fan, 23 mm without, on a 95 x 95 mm footprint. Noctua says that footprint fits inside Intel's LGA 115x keep-out zone, so it clears tall RAM and the graphics slot on mini-ITX boards. The fan is a 92 x 92 x 14 mm NF-A9x14 PWM, and NT-H1 paste plus a low-noise adaptor come in the box. Buy the original NH-L9i for LGA 1151: Noctua lists it for LGA 1156, 1155, 1150, 1151 and 1200. The NH-L9i-17xx version is for LGA 1700 and later only.
Noctua says the NH-L9i is not meant for overclocking and asks for care above 65 W TDP. Pair it with a T-series chip, a Pentium or a 65 W i3, i5 or i7, not a K chip. If you use the low-noise adaptor, Noctua's manual tells you to watch CPU temperatures and remove the adaptor if cooling falls short. If your case allows 65 mm, the Noctua NH-L9x65 is the step up: a 92 mm slim fan over a taller fin stack, no RAM or PCIe overhang, and Noctua aims it at low to moderate heat loads.
Side by side
| Cooler | Type | Height with fan | Fans | Intel mount listed | Suits |
|---|---|---|---|---|---|
| Thermalright Peerless Assassin 120 SE | Dual tower | 155 mm | 2 x 120 mm | 115X, 1200, 1700, 1851 | i7-8700K, i7-9700K, i9-9900K |
| Noctua NH-U12S | Single tower, 45 mm deep fins | 158 mm | 1 x 120 mm | LGA1151 and the rest of 115x, 1200, 1700, 1851 | 65 W to 95 W chips |
| ARCTIC Freezer 7 X CO | Compact tower | 132.5 mm | 1 x 100 mm | 115x, 1200, 775 | 54 to 65 W chips |
| Noctua NH-L9i | Low-profile top-down | 37 mm | 1 x 92 mm slim | LGA1151 and the rest of 115x, 1200 | 35 to 65 W chips |
Fitting it to an LGA 1151 board
- NH-U12S: a backplate goes behind the board, black NM-IPS1 spacers on its bolts for LGA 115x, then the mounting bars in hole position 1, then the heatsink. Noctua's manual warns you may need to remove the motherboard to fit the backplate.
- NH-L9i: four screws go in from the rear of the board, so you need a tray cutout or the board out on the bench.
- Freezer 7 X CO: ARCTIC's mounting frame is designed to go on with the board still in the case.
For LGA 115x, Noctua asks for a single 4 to 5 mm dot of paste in the center of the heat spreader. Clean off the old paste with isopropyl alcohol first; if your cooler brings no paste, a tube of non-conductive thermal paste is all you add. Our repasting guide walks through the cleanup and the first temperature check.
Questions
Will an LGA 1150 cooler fit an LGA 1151 board?
Yes. Intel's LGA 1155 and 1156 drawings put the heatsink holes on a 75 mm square, and Noctua says the mounting is identical across LGA 1150, 1151, 1155 and 1156, and LGA 1200 as well. Coolers sold for any of them fit.
Can I reuse the push-pin cooler from my old LGA 1155 PC?
It will mount, because the holes match. Intel's reference coolers for LGA 1155 were short aluminum extrusions sized for the chip they shipped with, so check the chip's TDP in the table above before you trust one with a 95 W K chip.
Sources and further reading
- Intel, 2nd Generation Intel Core and LGA1155 Socket: Thermal Mechanical Specifications and Design Guidelines, document 324644-004, May 2011 (Figure B-1: 75.00 mm heatsink hole spacing)
- Intel product specifications: Core i7-6700T, Core i7-6700, Core i7-6700K, Pentium G4560, Core i7-7700K, Core i3-8100, Core i5-8400, Core i7-8700K, Core i7-9700K, Core i9-9900K and Core i9-9900KS
- Noctua, FAQ: Is the cooler compatible with the LGA1151 socket? and FAQ: Which Noctua CPU coolers are compatible with Intel LGA1200?
- Noctua, NH-U12S specifications and installation manual
- Noctua, NH-L9i specifications, installation manual and TDP guidelines
- Thermalright, Peerless Assassin 120 SE
- ARCTIC, Freezer 7 X CO and its spec sheet
- Wikipedia, LGA 1151 (chipset background)
Ben keeps the web design corner: beginner HTML, CSS and JavaScript lessons with code you can paste and run. He also writes the general tech notes, usually after untangling something that should have been simple.
