Microsoft on Tuesday provided new details on the performance impact of updates to protect against recently disclosed security vulnerabilities. In certain cases, performance on Windows will be significantly slowed by patches for the Meltdown and Spectre vulnerabilities.

Some people have found that that their servers and PCs are performing differently after installing updates, so the news shouldn’t come as a big surprise. Still, the new information doesn’t line up perfectly well with what Intel said last week when the vulnerabilities were first officially announced. “Any performance impacts are workload-dependent, and, for the average computer user, should not be significant,” the chipmaker said.

Microsoft expects most people using Windows 7 and Windows 8 on chips that are from 2015 or older than that will notice performance degradations, Terry Myerson, executive vice president for Microsoft’s Windows and Devices Group, wrote in a blog post. The company did not publish specific performance benchmarks to back up the claims.

Some people using Windows 10 with Intel Haswell chips or anything older will notice performance impacts, Myerson wrote. But for those people running Windows 10 on Skylake, Kaby Lake, or newer Intel chips probably won’t notice performance issues, although internally run benchmarks show single-digit slowdowns, Myerson wrote.

The case is different for Windows Server, Microsoft’s operating system for servers. Should customers choose to install updates to protect against issues stemming from untrusted code running on those machines, there will be a more significant performance impact, Myerson wrote. “This is why you want to be careful to evaluate the risk of untrusted code for each Windows Server instance, and balance the security versus performance tradeoff for your environment,” he wrote.

At this point, Microsoft has provided Meltdown and Spectre patches for 41 of the 45 versions of Windows through Windows Update, Myerson wrote.

Intel stock went down after Microsoft released the news. It traded as low as $43.75, about 2 percent lower than opening price, falling from about $44.34 per share immediately after the announcement. Microsoft stock initially faltered but then reversed its decline.

Source: Tech CNBC
Microsoft says Meltdown and Spectre fixes will slow some PCs down significantly