Apple rolled out iOS 11.2.2 a few days ago to address Spectre vulnerability in iPhone and iPad, but the company hasn’t detailed one important concern: does the patch slow down devices as it happens on Windows?

And as it turns out, it does, with a series of benchmarks confirming that in some cases, an iPhone 6 can get even 50 percent slower after installing Apple’s security updates.

Melvin of conducted single-core and multi-core performance benchmarks on an iPhone 6 with no jailbreak, battery changes, or apps running in the background, in the end discovering a performance change of -41% in the case of the first tests and -39% of the latter.

The biggest performance hit was experienced in single-core benchmarks where the iPhone 6 dropped from 1761 points in HTML5 DOM tests to 778 points after installing the Spectre patches. This is a drop of 56% in performance.

“No measurable impact”

Apple hasn’t provided too many details on the performance hit that its devices could experience after installing security patches, with the company only saying the following in its Spectre FAQ:

“Our current testing indicates that the Safari mitigations have no measurable impact on the Speedometer and ARES-6 tests and an impact of less than 2.5% on the JetStream benchmark.”

Long-time rival Microsoft pledged for more transparency, and the company recently confirmed that Meltdown and Spectre updates indeed slow down Windows PCs, adding that the older the hardware gets, the bigger the impact on device performance. The same thing could apply in Apple’s case as well, as the tests were performed on an old iPhone 6, and it’ll be interesting to compare before and after patching performance on an iPhone X.

“Older versions of Windows have a larger performance impact because Windows 7 and Windows 8 have more user-kernel transitions because of legacy design decisions, such as all font rendering taking place in the kernel,” Microsoft explained.

It remains to be seen if Apple publishes similar figures on iPhone performance impact, but given the existing controversy, there’s no doubt the company should do this as soon as possible.

iPhone 6 benchmarks before and after patching