Intel Core i9-11900K & Core i5-11600K Is Intel back in the game?

It’s hard to imagine that every generation of Intel desktop processor released since August 2015 is based on the Skylake architecture. Processors since that era, up to and including the i9-10900K all used the successful Skylake building blocks.

That makes Intel’s new Rocket Lake 11th generation a hugely significant family of CPUs. It represents the company’s first architectural redesign in almost six years.

Intel’s struggles with 10nm manufacturing have been well documented over the last few years, yet here we are in 2021 still talking about it. At least there’s light at the end of the tunnel. 10nm is ramping quickly, though it’s still not ready for desktop prime time. With Skylake and 14nm having been milked for every last drop, with core counts and clock speeds maxed out, the only way to keep pace with AMD was to backport the 10nm Sunny Cove architecture to the mature (aka geriatric) 14nm process. That brings us to today. Here for review we have the highly anticipated 11th Generation Core i9-11900K and Core i5-11600K.

So what’s new?

11th Generation processors feature enhanced IPC and an improved multi-core boosting algorithm. There’s the long awaited PCIe 4.0 support and notably, an all-new iGPU based on the new Xe architecture. Though its usefulness is limited on the high-end models, this IGP is a very welcome upgrade for the lower tier models both for its performance improvements and upgraded video engine. Sadly, there’s no HDMI 2.1 support though. Rocket Lake also introduces new hardware accelerated AI functions and AVX-512 instruction support. This means that software that supports these instructions will run much faster compared to 10th Gen CPUs. 11th Gen CPUs are compatible with Z490 motherboards after a BIOS update though PCIe 4.0 support will depend on the motherboard.

11th Gen processors bring some cool overclocking features, including the ability to change memory frequency on the fly. There’s also a new memory divider, or Gear 2 which decouples the memory controller from the memory frequency. This means that memory overclocking is greatly improved. We’ll go more into this in our upcoming Z590 motherboard feature.

At the high end

The 11900K is an 8-core/16thread CPU with a 125W TDP, though that’s a meaningless number. It will suck up to 251W for short durations or even more under certain loads. As an i9 model, it features additional turbo functionality called Adaptive Boost. Essentially, the better your cooling and motherboard power delivery is, the higher the CPU can boost when using all cores, in fact, up to 5.1GHz with all cores. It sounds impressive, and in a way, it is, but there’s a heavy power and temperature cost to pay. If your cooling is not top of the line, forget it.

The mid-range

The 11600K is a 6-core/12 thread model with the same 125W TDP of its bigger K brothers. It’s a 6-core/12-thread model with a 3.9GHz base clock and a 4.9GHz boost clock. It’s not as demanding on cooling as the 11900K and its $419 price makes it a much more compelling option under loads that don’t require huge multithreading power. It’s one for

“Intel’s struggles with 10nm manufacturing have been well documented over the last few years, yet here we are in 2021 still talking about it.”

gamers to keep an eye on.

For our testing we are running the processors according to the Intel specification, with all motherboard specific enhancements disabled. We’ve included an additional set of results to show the effects of Adaptive Boost which is exclusive to the i9 CPUs. Notably, Intel does not define it as overclocking. Adaptive Boost improves multithreading performance by a lot, but as expected, it causes power consumption to skyrocket.

Performance

We were expecting more from both CPUs. They’re better at gaming and single threaded performance is improved, but there’s no getting around the fact that the 11900K loses two cores compared to the 10900K. Its performance is expectedly impressive under AVX loads, which is a win. The 11600K fares better compared to the 10600K but the performance alone isn’t enough to see off the threat of AMD’s very impressive Zen 3 CPUs.

As we indicated, the Achilles heel of 11th Gen CPUs is their heat output and power consumption. It’s not shocking under a typical workload, but with Adaptive Boost enabled, the 11900K can consume well over 300W under a heavy AVX load. That’s in the ballpark of 64 core Threadripper! And it also hit 100c despite using a quality 360mm AIO cooler. Thankfully, the 11600K fared a lot better with a maximum recorded peak of 189W under an all core AVX load and a peak temperature of 81c. Note that our initial testing appears to be highly variable depending on the motherboard. Some boards play fast and loose with power application, and it may be that 350W or even more is possible with an 11900K. Frankly, that’s obscene.

We didn’t waste our time trying to overclock the 11900K, it’s already beyond the limits of our cooling. The 11600K also didn’t give us a lot, with a 5.1GHz all-core overclock. We’d consider that to be adequate, but not really worth incurring a further loss of power efficiency.

One step sideways, one step back

We had high hopes for Rocket Lake, but the 14nm process and resulting inefficiency take all the shine off of it. The 11900K generally beats out the 5800X, but only with a brute force approach. It’s better at multi-threading, but if you’re buying it for that, you’re better off with a 5900X or 10900K. We’re happy to see PCIe 4.0 and the Xe integrated graphics but key new features such as AVX-512 and the AI specific instructions are of very limited value to the average desktop buyer. If you’re a gamer the tradeoffs don’t justify the upgrade either. Affordable 10th generation CPUs and Ryzen 5000 CPUs are simply smarter buys right now. Rocket Lake is a stop gap solution that should not exist.

If you have the cooling to tame it, the 11900K is a very fast CPU – a very fast 8-core CPU that’s expensive – that is. There’s no sidestepping the fact that the 11900K is a regression in value and core count compared to the 10900K and AMD remains unchallenged with its 12- and 16-core options. The 11600K is something else. It’s still a hot running CPU and it will never challenge higher core count models for multi-threaded performance, but it offers good gaming performance and value for money. It brings the improved Rocket Lake features all without the runaway power consumption. If its power efficiency could match that of AMD, we’d happily recommend it. For now, we think AMD Ryzen 5000 CPUs and Intel’s own 10th generation CPUs are better buys. The 11900K retakes the gaming crown, but at what cost? Perhaps 12th generation CPUs might be the game changers we hoped 11th Gen would be.