Intel, Microsoft, and other companies have warned that some PCs may see performance decreases as a result of security patches to fix the Spectre and Meltdown security flaws disclosed earlier this month. We tested four PCs from a variety of manufacturers that were updated in mid-January to protect against the flaws and found that while each of the systems did suffer a slowdown in computing performance, it's slight enough that most users won't notice the difference.

The Spectre and Meltdown code names refer to vulnerabilities in the way the CPU anticipates and prepares for future commands in order to perform them faster, a process known as speculative execution. Security researchers found that hackers could theoretically access these commands-in-waiting, which could enable them to steal sensitive information like usernames and passwords.

The speculative execution vulnerability is one of the most significant processor security flaws ever discovered, because it affects so many types of consumer electronic devices. Many products—not just PCs—that contain chips from Intel, ARM, and AMD are susceptible, but it is PCs that have born the brunt of the attention, mainly because fixing the flaws could make them slower.

How Much Slower?

The degree to which computing performance suffers as a result of the mitigations against Spectre and Meltdown depends on how you use your PC and how old and powerful its processor is to begin with. "For most consumer devices," Microsoft said in a statement, "the impact may not be noticeable, however, the specific impact varies by hardware generation and implementation by the chip manufacturer."

In other words, the Spectre and Meltdown fixes are like any other system update: They'll likely have more of a performance impact depending on how well your PC maker has adapted them to your hardware. That's a difficult thing to evaluate, but we attempted to do so by comparing the performance of four laptops with the latest software updates with their performance when we first tested them last year, before Spectre and Meltdown became known.

Our comparisons are based on two catch-all benchmarks. We used the PCMark 8 test to measure the computer's performance on web browsing, video conferencing, and many other tasks that consumers use their PCs to accomplish on a regular basis. We also ran the Cinebench 3D rendering simulation, which simulates a more processor-intensive workflow that professionals like video editors and architectural designers are likely to perform. These are a subset of our full testing regime; for more, read about how we test laptops.

Each of the machines we re-tested have the latest operating system updates installed directly from Microsoft or Apple, which means they have software-level protection against Spectre and Meltdown, since both companies released mitigations by last week. Intel says that firmware updates for 90 percent of its chips manufactured in the last five years are now ready, but it's up to the manufacturer to test them and roll them out to PCs. Each of the Windows systems we tested had these firmware updates installed either from the manufacturer website or from the software update utility, a process that involves flashing the BIOS.

The Results

Here's the bad news: Each of the Windows laptops we tested saw slight decreases in their PCMark scores, which suggests that the updates have a wide-ranging effect on everyday performance. However, the good news is that the difference is negligible. On the PCMark benchmark, which delivers a proprietary cumulative score, a difference of a few hundred points or so is trivial. What's more, any PC that scores above 3,000 on this test is an excellent all-around performer, able to handle common computing tasks like starting up apps and loading websites with negligible waiting time.

The Dell Latitude 7389 had the biggest PCMark score drop, from 3,323 to 3,263, or 60 points. The HP EliteBook 1040 G4 dropped by 44 points, to 3,510. The only system to score below 3,000 was the Microsoft Surface Laptop, but it also had a very slight decrease, from 2,745 to 2,690. Macs can't run PCMark.

The story was mostly the same on the Cinebench test. Each of the systems recorded a drop of between a few points to a few dozen points. The most consistent was the Surface Laptop, which decreased from 324 to 320. The biggest drop belongs to the Apple MacBook Pro , which decreased 68 points, from 374 to 306. Curiously, the EliteBook recorded an increase with Cinebench, which could mean that HP delivered some performance optimizations in a recent update independent of the security patches, or signal an anomaly on our original test.

These numbers should reassure the majority of PC users, since they largely confirm several manufacturers' claims that performance hits are negligible. On the other hand, people who use screaming-fast, Intel Xeon-powered workstations and companies that manage server farms will likely want to run their own tests to evaluate the effects of the Spectre and Meltdown mitigations.

Each system we tested uses an Intel Core i5 or Core i7 processor. On February 20, about a month after we performed the retests, Intel released a new round of firmware updates, including many for seventh- and eigth- generation Core processors, so it's possible that our results differ from what you might experience if you have a system with the latest patches. For more on how to protect your PC, visit our guide.

Further Reading

Processor Reviews