Hands-on review: Intel 11th-Gen Core i9-11900K and Core i5-11600K

Intel's 11th Gen Core S-series desktop processors, code-named Rocket Lake-S are now in the wild. We were sent an Intel Core i9-11900K and a Core i5-11600K to put through their paces. Intel also supplied an ASUS Republic of Gamers Maximus XIII Hero motherboard with the new Z590 chipset to test it all with.

Intel's 11th Gen CPUs still utilise 14nm silicon the same as their predecessors. As with the 9th and 10th generation of Intel CPUs, the Rocket Lake chips use an LGA 1200 socket. Except for the H410 and B460-based boards, they are also compatible with last year's 400-series chipset motherboards (subject to bios updates). This means that you can likely slot a new i5 or i9 in as a replacement for your 10th Gen CPU. But should you?

The "K" suffix denotes that the CPU is unlocked and suitable for overclocking. There's a premium for this over the locked version of the CPU over the regular version. The KH versions of the chips are the same as the K versions but without the Intel Xe-LP-based UHD integrated GPU. There's some money to be saved if you are not interested in overclocking or the on-board graphics capabilities.

Whilst owners of select 400-series motherboards can run Intel's Rocket Lake CPUs, to get the very best out of them, you'll likely be looking to pair them with a motherboard boasting Intel's new 500-series chipset.

You really can't beat ASUS motherboards and the Z590 ROG Maximus XIII Hero is no exception. Whilst in the past I've had issues with them, that was a long time ago. Nowadays ASUS produces motherboards that are both virtually plug and play, but also feature the advanced settings required of seasoned overclockers and PC tinkerers.

The easy-to-use UEFI BIOS menu puts control of the inner workings of a PC right at hand. AI overclocking can still give mixed results, but for most will give a performance boost without much in the way of overclocking knowledge, but more on that later.

The big selling points of the ASUS Z590 board are native PCIe 4.0 support, 2x Thunderbolt 4 (USB Type-C) ports, and a header for a front USB USB 3.2 Gen 2×2, as well as Wi-Fi 6E. It's also got two m.2 slots running at PCIe 4.0 x4 and another two running PCIe 4.0 x4.

Setup was relatively painless, with the Asus motherboard pretty much self-configuring to the 11th Generation processors. I tested both the CPUs using Passmark's Performance Test software (CPU only), Cinebench R23, 3DMark (CPU score only) and the Blender benchmark. I didn't check any games, as they only really benchmark the GPU performance.

The benchmark results were all rather predictable showing notable gains for the i9-11900K over last year's i9-10900K, with the more modest Core i5-11600K doing a good job of catching up, at the rear. I was surprised to see the Core i5-11600K beat the i9-10900K in all but one of the Blench benchmarks. The i5-111600K performed will in the single-core Cinebench test as well, again beating the i9-10900K.

Interestingly, for the i9-11900K, Intel has dropped the core count from the ten of the i9 10900K to only eight. This is likely a limitation of the 14nm fabrication process. Even so, the 11th Gen i9 beat the 10th Gen i9 15226 to 14043 in the Cinebench R23 multi-core test.

The Core i9-11900K base clock rate is 3.5GHz with an all-core turbo of 4.8 GHz and a max boost via turbo Boost 3.0 to 5.2GHz. The Core i5-11600K has a base clock rate of 3.90 GHz with an all-core turbo of 4.6 GHz and a max boost of 4.90 GHz.

Realistically, this means that providing the CPUs are running at less than 70 degrees C, for two cores you may see that max boost (utilising Intel Thermal Velocity Boost), but as soon as there are more than two active cores the frequency will reduce (across all active cores) to 4.8 GHz for the i9 and 4.6 GHz for the six-core i5.

Stress testing both CPUs, I managed to get the i9 to 5.1 GHz but suffered some thermal throttling. It's a warm chip like its predecessor. I was using a 2x120mm AIO cooler, nothing flash, so I wasn't too surprised by this. It would be good, however, if Intel were a little clearer and realistic with their marketing, though. With some tweaking, I'll likely be able to get more out of i9, but that's outside the scope of this review. The i5 boosted to 4.90 GHz without issue.

Both the CPUs also have native support for DDR4-3200 memory. With a 500-Series motherboard, they support up to 20 CPU lanes of PCIe 4.0. A motherboard with an Intel 500-series chipset, once equipped with an 11th Gen Intel CPU, unlocks the PCIe 4.0 x4 M.2 socket (one of four M.2 sockets on the ROG Maximus board).

I was able to install a WD_Black SN850 NVMe SSD and get a rather spectacular 6966.76 MB/s Read and a 5368.31 MB/s write speed. Compare this to the rather pedestrian 130 MB/s read and 65 MB/s write for a regular hard disk.

I did have a little dabble with the ASUS AI overclocking tool accessible from the Maximus XII motherboard bios. I've had a lot of success carrying out quick and nasty overclocks using earlier iterations of this tool. Despite running the Intel Extreme Performance tool to train it, the Asus board's AI overclocking decided that for the i9 11900K a 51% overclock was in order.

This proved unstable and in need of a bit more messing about than I had time for. I'm sure I can get a stable OC, but perhaps not 51% with a moderate AIO cooler. The i5's AI overclock was a more modest 31%, but still not stable. I'm not saying that overclocking is out of the question with these CPUs, but a better cooler or some fan adjustments may be needed.

The on-board UHD 750 GPU, whilst not in the same league as a discreet gaming graphics card like an RTX 3070, is not bad if you are not interested in hardcore gaming. The UHD 750 scored a very modest 635 graphics score in 3D Mark Timespy compared to the score of 3724 with a five-year-old GTX 1060 GPU. In theory, though, you could play something like Battlefield V, but I wouldn't expect to be able to get much more than 30 fps out of it, even with the graphics turned down.

For something like Photoshop or even video editing software, you should be able to get by with the UHD 750, if not exactly the optimal experience. More demanding graphics applications really need a dedicated graphics solution.  If you have no need for the integrated graphics, getting the KF version of the CPU, that has no on-board GPU, will save you 50 bucks or so.

With an RTX 2080 Ti plus a Gen 4 WD_Black SN850 NVMe SDD in the motherboard, Passmark gave both the i5 and i9 configurations a 99-percentile result, putting them in the top 1% of machines tested. This is something that's not to be sneezed at.

Whilst this is all very exciting stuff, as a consumer, I can't help but think that this technology is being deliberately trickled out to fuel an annual iteration of motherboards with noteworthy if moderate, enhancements.

To be honest there's nothing here that says that the average PC user needs to replace their computer more frequently than every five years. Even PC gamers should be OK for three years, with only the most dedicated requiring an upgrade every two years. Apart from bragging rights, there is no need to upgrade your PC components annually.

Intel's 11th Gen CPUs and the Z500-series chipset are engineered to offer enough to differentiate between last year's PC models and this year's. If you are in the market for a new PC the Z590's connectivity alone, especially the native PCIe 4.0, is worth the investment. But, if you are still rocking a Z490 and a 10th-Gen CPU, you are not really going to get the bang for your buck.

There's no doubt that both the Intel Core i9-11900K and Core i5-11600K are fantastic CPUs if only a modest upgrade from last year's components. I'd say that the i9 is reserved for enthusiasts, with the i5 being more suited to general PC tasks and even high-end gaming. Nevertheless, if only for the benefits of the 500-series motherboard chipset opened up by the 11th Gen, these are the CPUs for those that want the best desktop solutions that Intel has to offer.