iPhone 6 takes massive performance hit after Spectre patch

12 January 2018

We always knew that patching the recently-discovered Meltdown and Spectre vulnerabilities will involve a drop in performance, especially in older devices. The magnitude of the drop is still being examined, but the early results donít look good.

In at least one case, an iPhone 6 saw its Apple A8 lose 40% of its CPU performance after going from iOS 11.1.2 to 11.2.2. The test was run by Dutch entrepreneur Melvin Mughal who got the following results on his phone before and after the update.

Before Spectre update After Spectre update Performance change
iPhone type iPhone 6
iOS version iOS 11.1.2 iOS 11.2.2
Single-Core Score 1561 924 -41%
Multi-Core Score 2665 1616 -39%

Both single and multi-core performance are strongly affected and memory access took a hit as well. That was to be expected as both vulnerabilities exploit the CPUís cache.

Since the test was run on the same phone, the scores are not affected by the battery-related slowdown. That does make it harder to collect more data, however.

For example, hereís one result from Geekbenchís database where the scores remain on pre-update levels and another one, which is closer to Melvinís numbers. There are more 11.2.2 scores like that, but itís hard to tell how much of the inconsistency is due to throttling due to an old battery.