Intel Core i9-9900K socket: LGA 1151

What the Core i9-9900K is

The Core i9-9900K is the top model of Intel's 9th Gen desktop family, announced in October 2018 with the codename Coffee Lake Refresh. It has eight cores and sixteen threads, a 3.6 GHz base clock and a single core boost to 5.0 GHz. It was the first Core i9 that Intel sold for its mainstream desktop socket, which until then had topped out at Core i7.

The processor is built on a 14 nm process like the generations before it. The L3 cache is 16 MB, shared by all cores, and Intel rates the base power at 95 W. It includes Intel UHD Graphics 630, so a screen can run without a graphics card, and the multiplier is unlocked for overclocking. Intel's recommended price at launch was $488 in 1,000 unit quantities.

Intel also sold the Core i9-9900KF with the integrated graphics disabled. Because the 9900K uses a revision of LGA 1151 that differs from the first one, the details of the socket matter more here than for most chips.

Socket and motherboard compatibility

The Core i9-9900K goes into an LGA 1151 socket, but only the second revision of it. That revision is used by boards with 300 series chipsets: Z390, B365, Z370, H370, B360, H310 and Q370. Boards with 100 or 200 series chipsets, such as Z170 or Z270, look the same and take the same size of chip, but Intel and the board makers do not support it there, and a BIOS update does not change that.

Z390 and B365 boards were launched for the 9th Gen processors, so they start with the 9900K out of the box. Boards with Z370, H370, B360, H310 and Q370 chipsets were made for the 8th Gen, and they need a BIOS update before a 9th Gen processor will start. Buying a used Z370 board makes this a real concern, since the update has to be done before the 9900K is installed. The board maker's CPU support list gives the exact BIOS version.

Only Z-series boards unlock the multiplier. The 9900K can run on an H310 board, but that is a poor match, because entry boards often have power delivery that limits an eight core chip.

Memory, PCIe and cooling

The memory controller supports DDR4 at up to 2666 MT/s, across two channels and up to 128 GB. Revision 2 boards use DDR4 only, so older DDR3 modules cannot be reused. Faster kits work through XMP profiles on boards that allow it.

PCIe lanes from the processor run at version 3.0, with 16 lanes for graphics. There is no PCIe 4.0 on this platform, which came with later sockets.

The 75 mm mounting holes are shared with LGA 1155, 1150 and 1200, so older Intel coolers normally fit. With a 95 W rating the chip is a heavy load for a small cooler, and it can draw more under all core turbo. Intel does not include a cooler with the K-series, so a tower air cooler or a liquid cooler has to be bought separately. See the CPU cooler compatibility by socket guide for the mounting patterns.

Upgrade paths

The 9900K and its higher clocked sibling, the Core i9-9900KS, are the fastest chips for revision 2 boards, so a bigger upgrade means a new platform. The nearest step is LGA 1200, which is not compatible with LGA 1151 processors, even though the package size is the same.

Compared with newer chips, an eight core processor with 16 threads still handles ordinary workloads. A move to LGA 1700 with a chip like the Intel Core i5-12400F brings newer cores with fewer of them, a faster memory standard and PCIe 4.0 or 5.0.