Intel Core i9-11900K and Core i5-11600K Review: Rocket Lake Blasts Off

Intel 11th-Gen Core Rocket Lake Xe Graphics 

Most Rocket Lake chips come with the UHD Graphics 750 engine powered by 32 EUs with the Xe architecture. Intel has carved the Xe LP graphics engine into UHD Graphics 750 (GT1) with 32 EUs and UHD Graphics 730 (GT1) with 24 EUs. The latter makes an appearance on the Core i5-11400 (T and F) chips. Intel also added new features to the graphics engine, with HEVC, VP9, and SCC encoders that support up to 4K60 12b and hardware-accelerated AV1 decode support for 4K60 10b.

Intel dedicated more die area to the graphics engine than it did with Comet Lake, noting that not only has it increased the number of EUs from 24 to 32, but the EUs are also physically larger than prior 14nm EUs. The increased iGPU real estate was a factor in Rocket's limitation of eight CPU cores.

Intel bases its 50% generational iGPU performance improvement claim on the 3DMark Firestrike GPU benchmark, and as with all synthetic gaming tests, those results don't translate well to real-world gaming. As such, you should take those predictions with a grain of salt. 

As before, you're free to overclock the graphics engine and Intel says it benefits from increased memory bandwidth, so memory overclocking pays dividends.

We took the new graphics engine for a spin, but our initial results were lacking and we encountered as-yet unexplained compatibility issues with a few titles. We're investigating further and will follow up with test results once we've diagnosed the issue. 

500-Series Chipset, PCIe 4.0, and Rocket Lake Compatibility 

Given that the Rocket Lake 500-series motherboards come with the same physical LGA 1200 socket dimensions as the 400-series, existing LGA 1200 coolers are compatible between the two series. As per usual with Intel's newer Core i9 chips, you'll want to use either a top-end air or 240mm (or greater) AIO liquid cooler to unlock the best performance, though you could get away with much less extreme coolers for the downstream models.

Intel has now enabled memory overclocking on its B560 and H570 chipsets, and that will work with any chip that is compatible with the platform, meaning all 10th-Gen Comet Lake, 11th-Gen Rocket Lake, and 11th-Gen Comet Lake Refresh processors.

Rocket Lake is the first Intel lineup for desktop PCs that supports the PCIe 4.0 interface, a needed addition that comes two years after AMD introduced the first PC chips to support the interface. Intel also reworked Rocket's internal PCIe subsystem to accommodate a direct x4 connection for M.2 SSDs and a x16 graphics connection to the CPU (the chips now support 20 lanes of PCIe 4.0).

However, the 500-series chipset only supports 24 lanes of PCIe 3.0 connectivity — not PCIe 4.0. Intel says this is because it had PCIe 4.0 IP ready for its chip, but not for the chipset. That means you'll only find one PCIe 4.0 M.2 slot on 500-series motherboards. 

The Rocket Lake PCIe 4.0 motherboard support matrix is complicated. Rocket Lake-S chips are backward compatible with Z470 and H470 chipsets, and PCIe 4.0 will work on motherboards that support the interface. However, Rocket Lake-S isn't compatible with H410 and B460 chipsets because they use an older chipset.

Intel also widened the DMI 3.0 connection (the pathway that connects the CPU and chipset) from four lanes to eight, doubling throughput up to a theoretical ~7.86 GB/s. Even though Intel widened the DMI bus, it still operates at speeds similar to PCIe 3.0. 

The wider DMI connection should help with bottlenecks for devices attached to the chipset, like SSDs in RAID, but caveats apply. Rocket Lake's wider x8 DMI connection is also only active on 'select' 500-series chipsets, so the chip defaults to a x4 connection on B560 and H510 motherboards. The same x4 connection applies if you use a Rocket Lake processor in a 400-series motherboard. 

Most Comet Lake chips are forward-compatible with the new 500-series motherboards that debuted recently, the lone exception being Celeron models with 2MB of CPU cache. Comet Lake chips also only use a x4 DMI connection on all 500-series motherboards. We have a deeper dive into the chipset and forty-five Z590 motherboards for Rocket Lake and Comet Lake processors here. You can also follow this link to see the differences between Intel's Z590, H570, B560, and H510 chipsets. 

Core i9-11900K and Core i5-11600K Gear 1 and Gear 2 Memory Modes 

Intel's new Gear 1 and Gear 2 modes present yet another new testing parameter, so we tested the performance impact in gaming between the two modes. As a reminder, Gear 1 is the optimal setting with the memory and memory controller operating at the same speed (1:1), which is best for low-latency applications like gaming. Gear 2 allows the memory to operate at twice the speed of the memory controller (2:1) and results in higher data transfer rates but also higher latency.

This setting adheres to the JEDEC Gear specification and is similar to AMD's arrangement with its Ryzen 5000 chips, but Intel's implementation is different: The functional maximum memory overclocking limit of Gear 1 falls between DDR4-3600 and DDR4-3800, depending on chip quality. Also, there isn't a method to increase Rocket's memory frequency beyond DDR4-3800 and remain in a 1:1 ratio (unlike AMD's 1:1 implementation that can be extended by adjusting the fabric ratio).

This presents an issue with the Core i5-11600K, which, at stock settings, supports DDR4-3200 in 2:1 and DDR4-2933 in 1:1. We measured Gear 1 memory latency for DDR4-2933 (CL14) at 52.3ns and Gear 2 DDR4-3200 memory latency at 59.3ns (per AIDA). After testing, we found that the higher Gear 2 memory latency has a varying impact on different game titles, with memory-sensitive games like Far Cry 5 suffering the most (5% at 1080p), but most other titles declining in the 2% to 3% range. Due to these persistent deltas, we only presented the Core i5-11600K in Gear 1 mode with DDR4-2933 memory for our stock test results.

The new Gear modes also present a new challenge for Intel memory overclocking, which we encountered with the Core i9-11900K. With both Rocket Lake chips, we could only reach DDR4-3600 while remaining in a 1:1 ratio. Additional tuning and/or motherboard firmware refinements could yield better results in the future. 

To reach beyond our limit of DDR4-3600 to DDR4-4000, we toggled on Gear 2 mode with the Core i9-11900K and 11600K in tandem with our overclocked core frequencies. However, DDR4-4000 (C17) in Gear 2 mode resulted in lower performance in nearly every title in our test suite, leading us to test our overclocked configurations in 1:1 mode at DDR4-3600. We might rectify this with tighter timings or newer firmwares in the future, but time constraints came into play for this round of testing. Look to these pages for follow-up coverage on Rocket Lake memory scaling in the future. 

Test Setup 

Intel has recommended Power Level 1 (PL1 — boost power), Power Level 2 (PL2 — sustained power), and Tau (boost duration) variables for all of its chips, but motherboard vendors are free to exceed those recommendations, even at stock settings, to differentiate their motherboards. As such, performance has long varied by motherboard based on the respective power settings.

We're sticking with our standard policy of allowing the motherboard to exceed Intel's recommended power limits, provided the chip remains within warrantied operating conditions. Our tested settings reflect lifted PL1 and PL2 restrictions, which essentially removes the Tau limitation. Almost all enthusiast-class motherboards come with similar settings, so this reflects the out-of-box experience with a high-end motherboard. Naturally, these lifted power limits equate to more power consumption, and thus more heat, as we'll cover in detail later in the review.

Intel's combination of new Gear memory modes and power settings, including Adaptive Boost Technology (ABT), have created a wide array of potential configurations for testing. We've thoroughly tested the chips in numerous modes and chosen the most optimal configurations for our primary series of tests. We'll share data later in the review that quantifies the differences between the possible configurations, including details on the memory settings and performance in a power-limited scenario where we strictly limit our setup to Intel's recommended guidelines. Note that ABT comes disabled by default in the BIOS, but enabling this feature does not void your warranty.

However, to keep the charts readable while showing the differentiation between various features, we've chosen the following settings for our application and game testing with the Rocket Lake processors:

• Core i9-11900K ABT On: Stock configuration, Adaptive Boost Technology enabled, PL1 & PL2 limits lifted, DDR4-3200 in Gear 1 mode (stock memory configuration)
• Core i9-11900K ABT Off: Stock configuration, Adaptive Boost Technology disabled, PL1 & PL2 limits lifted, DDR4-3200 in Gear 1 mode (stock memory configuration)
• Core i9-11900K @ 5.2: Overclocked configuration, 5.2 GHz on all cores, -2 AVX2 offset, -5 AVX-512 offset, DDR4-3600 in Gear 1 mode
• Core i5-11600K: Stock configuration, PL1 & PL2 limits lifted, DDR4-2933 in Gear 1 mode
• Core i5-11600K @ 5.0: Overclocked configuration, 5.0 GHz on all cores, -2 AVX2 offset, -3 AVX-512 offset, DDR4-3600 in Gear 1 mode 

We'll share further details about our overclocking efforts and the test setup, along with boost, thermal, and power testing, on the following page. 

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