Microsoft explains how Meltdown and Spectre mitigation will affect PC performance

Microsoft says Windows 10 PCs will newer CPUs will see single-digit drop in performance while Windows 7 and Windows 8 machines with older CPU will be most affected after the patch.

  • Published: January 10, 2018 9:38 AM IST
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Meltdown and Spectre, two critical vulnerabilities affecting chipsets from Intel, AMD and ARM Holdings, were disclosed last week. While the patch for both the vulnerabilities were ready even before it was publicly disclosed, security researchers observed that the software fix could slow down performance by anywhere between 5 and 30 percent.

Microsoft, one of the many software developers releasing patches for its operating systems, is detailing how the Meltdown and Spectre fix may affect PC performance. The Redmond-based software giant reveals that most modern PCs running Windows 10 won’t be seeing significant difference in performance after updating their systems. However, those using older machines – particularly the ones running Windows 7 or Windows 8 – will see a noticeable drop in performance.

In a blog post, Microsoft Windows chief Terry Myerson explains that PCs running Windows 10 on newer Intel architecture like Skylake, Kaby Lake or any newer CPU show single-digit slowdowns and most users won’t notice the difference in performance in their workflow. But benchmarks show that Windows 10 on older silicon like Haswell or order show more significant slowdowns and users will notice the difference in system performance. Myerson also adds that PCs with older silicon and running Windows 7 or Windows 8 operating system will also notice a decrease in system performance. Microsoft also confirms that Windows Server will see significant performance impact in any IO-intensive application.

All processor architectures run programs by using speculative execution in order to crunch more data at a faster rate. Spectre basically fools the processor to run speculative operations in order to trace crucial data including passwords and private encryption keys. On newer CPU architecture like Skylake and beyond, Intel has refined the instruction set used to disable branch speculation to be more specific to indirect branches and it reduces the performance impact caused by the Spectre security patch.

The performance impact will be noticeable on Windows 7 and Windows 8 machines since they rely on more user-kernel transitions with features like font rendering taking place in the kernel. This will be impacted by the Spectre and Meltdown mitigation compared to Windows 10.

Microsoft also says the firmware updates for Meltdown and Spectre variant 2 have more performance impact compared to Variant 1 and Variant 3. To mitigate Meltdown and Spectre Variant 1, Microsoft has isolated kernel and user mode page tables and even patched Edge and Internet Explorer and prevent JavaScript exploits. It notes that patches are available for 41 of 45 editions of Windows and the remaining four editions will receive the patch soon.

“As you can tell, there is a lot to this topic of side-channel attack methods. We’re also committed to being as transparent and factual as possible to help our customers make the best possible decisions for their devices and the systems that run organizations around the world,” Myerson explains in his blog post.

Microsoft is the first company to offer details on how performance might get affected with Meltdown and Spectre mitigation. Apple and Google have not confirmed whether their devices are mitigated against Spectre Variant 2 and if there is any noticeable decline in performance. Most companies have already issued software updates to protect their browsers and operating systems against the vulnerabilities.

  • Published Date: January 10, 2018 9:38 AM IST