Intel Core i7-5820K: specs, X99 boards, DDR4 and buying one used

The Core i7-5820K is the entry-level processor of Intel's 2014 Haswell-E enthusiast line. People who go looking for one, new-old-stock or used, are usually upgrading or repairing an X99 system and want a six-core chip without changing the platform. This guide covers what it is, what it needs to run, how to confirm a chip is the genuine part, and what to check on a used one.

In this guide

Key specifications

From Intel's ARK page for the part:¹

The 5820K sits beside the Core i7-5930K (6 cores, 3.5 to 3.7 GHz) and the 8-core Core i7-5960X in the Haswell-E family. All use the LGA 2011-v3 socket with the X99 chipset and DDR4, and the family supports AVX2.² The 5820K's 28 PCIe lanes are the point most often raised in builds with several GPUs or NVMe cards; plan your slot usage around the lane count shown on ARK rather than the number of physical slots on the board.

Which motherboard and memory

The socket is LGA 2011-v3, which is not the same as the older LGA 2011 used by Sandy and Ivy Bridge-E. They differ in electrical signals, in the keying of the socket's independent loading mechanism, and in memory (DDR3 on the old socket, DDR4 on 2011-v3), so neither chip fits the other board.³ In practice:

• Use an X99 board with an LGA 2011-v3 socket.
• Use DDR4 only. A 5820K cannot use DDR3.
• Fill memory in multiples of four modules to use all four channels. Intel lists support to DDR4-2133; modules rated faster are normally run beyond that through the board's memory profile, which is a board-and-kit matter and not an Intel specification.
• Check the board vendor's CPU support list and BIOS version for this exact chip before ordering the board; support lists are specific to board model and BIOS release.

Cooler mounting also needs care. The LGA 2011 family used two different mounting patterns, 80 by 80 mm and 56 by 94 mm, depending on the socket's loading mechanism, so a cooler must match the board's type.³ A 140 W part also needs a proper cooler. Wikipedia notes that Haswell-E chips reach over 4.6 GHz overclocked but run noticeably hotter than their predecessors, so overclockers should budget for strong cooling.²

Who it still suits

It suits a person who already owns an X99 board and wants to replace a failed or lower-end chip, or a hobbyist building a budget multi-core system from used parts. Six cores and twelve threads with quad-channel memory remains workable for general use, virtual machines and light rendering. It will not match recent processors for efficiency or single-thread speed; for a new build, compare against current products and weigh the platform's age (the chip itself was discontinued in 2021).

Upgrade paths

Staying on the same socket, the options are:

• Within Haswell-E: the 5930K (6 cores) or 5960X (8 cores).²
• Broadwell-E: the 14 nm refresh from May 2016 uses the same LGA 2011-3 socket: Core i7-6800K and 6850K (6 cores), 6900K (8 cores) and 6950X (10 cores), with quad-channel DDR4-2400 support.⁴ Whether your board accepts them depends on the board's BIOS, so check the vendor's list and update the BIOS beforehand, ideally while your current processor is still installed.
• Xeon: Wikipedia lists the LGA 2011-v3 socket as used by Haswell and Broadwell-E and -EP parts, but whether a given X99 board accepts a Xeon is board-specific, so check the board's support list rather than assume.³

How to confirm it is the real part

Intel's ARK page is the authoritative reference. Match the markings on the chip and the box against it:

• The processor number is i7-5820K and the spec code is SR20S, stepping R2.⁵
• Intel lists these order codes: tray CM8064801548435, boxed BX80648I75820K, and a China-market box BXC80648I75820K.⁵
• On the chip's integrated heat spreader, the printed text should read as an i7-5820K with the SR20S code. Compare the markings, and check the print quality on the heat spreader against a known good photo.

A seller who gives you only a photo of the top of the chip is not giving you much to verify. Ask for photos of the markings, the underside (land pads) and the box label. If the box code does not match one of the codes above, ask why. Run CPU-Z or the operating system's system information once installed; the reported model, core count and clock should match the table above. Counterfeit and re-marked processors exist across the used market, so a quick stress test and temperature check on arrival is sensible.

Checking a used one

• Land pads and socket side. Look for scratches, discolouration or gouges on the contact pads. Damaged pads can cause unreliable memory or boot faults, and are grounds to reject the chip.
• Heat spreader. Check for dents, scratches from a cooler, or evidence that the lid has been removed. Chips can be delidded for cooling; that is not necessarily a defect but should be disclosed.
• Overclock history. Some buyers ask for chips that have not been overclocked, as one buyer did in a wanted post.⁶ Visual inspection cannot confirm this; ask the seller, then test stability yourself at stock settings.
• Test on arrival. Run a full stress test and monitor temperatures. Check that all 6 cores and 12 threads appear and that the board posts with memory in all four channels.
• Packaging and returns. Confirm the return terms before you pay, particularly for a discontinued part.

This page does not give price or availability information; check live listings and sold results.

Buying the CPU alone or an X99 bundle

A processor-only purchase makes sense when you already have a known-working board. When building from scratch, compare the complete cost of CPU, motherboard, DDR4, cooler and any missing mounting hardware. A cheap 5820K can become an expensive repair project if the accompanying board has damaged socket contacts or an undocumented fault.

Ask a bundle seller to demonstrate the actual combination, rather than send an old benchmark from a different motherboard. Useful evidence includes a BIOS screen identifying the processor and installed memory, a photo of the motherboard model printed on the PCB, and a recent test showing all memory channels working. A timestamped photo helps connect the test to the items being sold, although it does not replace a return policy.

Search terms that narrow the right listings

Use i7-5820K SR20S for the processor and the full board model for compatibility research. Search X99 5820K DDR4 bundle when you need the platform together. “LGA 2011” by itself is too broad because it also brings up older platforms and incompatible accessories.

Does the 5820K have integrated graphics?

Intel's processor page lists no processor graphics for this part.¹ Plan the build around a graphics solution supported by your motherboard and workload; do not assume that a display connector on an unfamiliar board will supply a picture with this CPU.

What should be tested first after arrival?

Start at the board's stock settings. Confirm the model and memory, check cooling, and test stability before changing memory profiles or overclock settings. That keeps a delivery fault easier to distinguish from a new configuration problem.

Sources and further reading

1. Intel Core i7-5820K Processor specifications, Intel ARK: manufacturer specifications.
2. Haswell (microarchitecture), Wikipedia: Haswell-E family and overclocking notes.
3. LGA 2011, Wikipedia: socket generations, DDR4 requirement and cooler mounting patterns.
4. Broadwell (microarchitecture), Wikipedia: Broadwell-E models.
5. Intel Core i7-5820K Processor ordering information, Intel ARK: spec code, stepping and order codes.
6. WTB: 5820K, [H]ard|Forum: a buyer's wanted post asking for a boxed or used chip, preferably not previously overclocked.