Intel Core i7 5820K 6-core LGA 2011-v3

The i7-5820K is a six-core Haswell-E chip that's dirt cheap on the used market, starting around USD 53 in the US. It overclocks like a champ and handles multithreaded work well, but it's power-hungry and needs an LGA 2011-v3 board. If you can live with the platform cost, it's one of the best budget multithreaded buys out there.

The 5820K posts a PassMark multi-core score of 9831, which lands it right around the middle of the pack in our database. Single-thread is 1992, also about average. That's not going to blow anyone away in 2024, but the six physical cores handle streaming, video editing, and multitasking without choking. The real story is overclocking. Owners routinely push these to 4.4GHz or higher on decent air or liquid cooling, and that's where the chip wakes up. The catch is the 28 PCIe lanes, which is stingy if you want dual GPUs plus a pile of NVMe drives. For a single-GPU setup, it's a non-issue.

Against something like the Ryzen 5 9600X, the 5820K gets stomped in single-thread and efficiency. The Ryzen sips power and screams in lightly threaded tasks. But the 5820K costs a fraction of the price and still delivers six real cores. The Dell Xeon E5-2637 V2 is a similar vintage but only four cores, so the i7 wins on multithreaded work. The Phenom II X6 is ancient by comparison and not worth your time. For pure budget multithreading, the 5820K holds its own against anything near its price.

This is where the 5820K gets interesting. US listings run from USD 53 to USD 170, and at the low end that's an absurd amount of compute per dollar. Newegg has the best US deal right now. European buyers see a wider spread, EUR 175 to EUR 294, which makes it less of a no-brainer across the pond. The catch is platform cost. LGA 2011-v3 boards aren't free, and DDR4 adds up. But if you can snag a cheap board, the total package undercuts any modern six-core by a mile.

The Core i7-5820K is old Haswell-E silicon, but it still has a trick up its sleeve: six cores and twelve threads for dirt cheap on the used market. We're talking USD 53 to USD 170 depending on where you look. That's a lot of multithreaded muscle for the money. It runs at 3.3GHz base and 3.6GHz boost, with 15MB of L3 cache and quad-channel DDR4 support.

You'll need an LGA 2011-v3 board and DDR4 RAM to make it work, and there's no cooler in the box. But if you're building a budget workstation or a cheap streaming rig, this chip is a legitimate option. The 140W TDP means it pulls real power, and efficiency is not its strong suit. Still, owners absolutely love this thing, and the sentiment data backs that up.

Skip this if you need strong single-thread performance for high-refresh gaming or lightly threaded apps. The efficiency score is one of the weakest in our database, so if power draw and heat matter to you, look at a modern Ryzen instead. Also skip it if you need lots of PCIe lanes for multiple GPUs or a pile of NVMe drives, the 28 lanes will frustrate you.

If you're building a cheap used workstation, streaming box, or just want a fun overclocking project, the 5820K is a fantastic buy. It's not efficient, it's not modern, and it won't win any single-thread races. But six cores with hyperthreading for under USD 100 in the US is hard to argue with. Pair it with a decent cooler and a budget X99 board, and you've got a surprisingly capable machine.