The Intel Core i9-9900KS Special Edition Review: 5.0 GHz on All the Cores, All the Time

R0 versus P0 Stepping IPC Testing

Intel has added new hardware-based mitigations for many of the new vulnerabilities, like MSBDS, Fallout, and Meltdown, with new steppings of its die. Our Core i9-9900KS processor comes with the R0 stepping (Stepping 13), which stands in contrast to our -9900K model with the P0 stepping. It is noteworthy that newer ninth-gen Core models also ship with the P0 stepping. These in-built mitigations are designed to ease the performance overhead of software-based Windows security patches.

These in-silicon fixes have been rumored to impact instructions per cycle (IPC) throughput, and we logged a few performance regressions compared to the Core i9-9900K during our first round of tests. After re-flashing the motherboard BIOS and deploying a larger suite of tests, we found that the regressions weren't as pronounced as we initially recorded.

We set a static 5 GHz clock rate and dialed memory to the respective processors' supported frequency for the following tests:

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As we can see, a few workloads do take a step backward, but most of the deltas fall within the expected run-to-run variance. Other workloads show slight gains. The LuxMark test registered a 4.5% standard deviation over our five test runs, meaning those results also fall within expectations given that that the test is inconsistent. As such, we will exclude that benchmark from future IPC testing. Our SHA-256 multi-threaded test represents the only significant outlier among the test suite that doesn't fall within the expected variance. It's important to remember that IPC can vary by workload, so dissimilar tasks may yield different outcomes.

However, we expect more pronounced performance improvements from the R0 silicon's in-built hardware mitigations. It's possible that these results could stem from motherboard firmware that isn't fully optimized. We have reached out to Intel for further information and will update as necessary.

Intel Core i9-9900KS Overclocking

We tested the Core i9-9900KS at stock settings with both a Corsair H115i cooler and a custom watercooling loop with an EKWB Supremacy Evo waterblock paired with two 360mm radiators to remove thermal limitations. 

We saw little to no performance variation stemming from the different coolers at stock settings throughout the full breadth of our application testing suite. 

We easily attained a 5.2 GHz overclock with the custom loop, and temperatures hovered between ~75C and 85C during extended stress tests (above). We set vCore at 1.36V, tuned the memory to DDR4-3600, and adjusted Load Line Calibration on our MSI Z390 Godlike motherboard to Level 3. FCLK adjustments also help with stability, so we adjusted the setting to 1000 MHz. 

We spent some time attempting to overclock with the Corsair H115i but didn't meet with much success as temperatures became a limiting factor. As such, we used the custom loop for our overclocking efforts in the test suite. 

Overall, the Core i9-9900KS proved to be an easy overclocker, but as always, your mileage may vary. You'll pay a pretty penny for the Core i9-9900KS, but your odds of getting a cherry chip are certainly improved.

Our Test Sample

We used an independently-sourced Core i9-9900KS sample for our exclusive early testing article but expressed reservations because it appeared to be pre-production silicon. After further investigation, we learned that our sample is from a production batch. We also learned that MSI will not issue a new BIOS immediately following the -9900KS launch, meaning our initial test results with the publicly-available BIOS are valid and representative of performance with a shipping Core i9-9900KS processor. As such, we're using many of the test results generated from our exclusive preview

A Note on Multi-Core Enhancement (MCE)

Intel's motherboard partners have infused their boards with predefined all-core boost profiles that go by many names, such as Multi-Core Enhancement (MCE) with ASUS motherboards and Enhanced Turbo with our MSI motherboard. These features are largely referred to as MCE, but the functionality remains the same: These settings essentially apply an all-core overclock to the processor that is defined by the maximum Turbo Boost bin supported by the processor. This setting modifies the CPU's clock rate and voltage to deliver higher performance, which is basically factory-sanctioned overclocking.

MSI turns this on by default in its BIOS, similar to most of its competition. Performance, power consumption, and heat are all affected, naturally. We manually disable this feature for our stock CPU testing to best reflect Intel's specifications. 

Test Methodology

We used Windows 10 version 18362.356 for our testing. All of our test results come from the aforementioned operating system and include all publicly available security mitigations. Intel is currently impacted by Spectre, Spectre v4, Meltdown, Foreshadow, Spectre v3a, Lazy FPU, Spoiler, and MDS, while AMD is only impacted by Spectre and Spectre v4. 

All applications, drivers, and motherboard firmware revisions (including AMD's boost-fixing ABBA AGESA code) are also up-to-date. 

MSI MEG Z390 Godlike

We're using MSI's MEG Z390 Godlike as our test platform for all Intel processors. This pricey board retails for $600, but has the power delivery subsystem to support aggressive overclocking.

The MEG Z390 Godlike sits at the top of MSI's motherboard hierarchy. It has a decked-out 18-phase power delivery subsystem that's designed to squeeze every drop of performance out of Intel's new processors. It also comes with a few nifty accessories like an M.2 PCIe riser card and an HDMI streaming card.

Test System and Configuration

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