Two weeks after the first patches for the far-reaching Spectre and Meltdown processor vulnerabilities started rolling out, many users are still not out of the woods.

The latest complication in the computer industry’s efforts to fix the problem involves Intel Corp., whose central processing unit chips are most heavily affected by the flaws. The chipmaker revealed late Wednesday that a serious problem with the patch that it has issued for users is much more widespread than previously believed.

The problem, which first came to light last Thursday, causes some machines to unexpectedly reboot and disrupt user activity. Intel originally said that the flaw only has a chance to manifest on computers with CPUs from the 2013 Haswell and 2014 Broadwell families. During internal testing, however, the chip maker’s engineers discovered that machines running practically all recent processors are potentially susceptible.

The number of affected Intel CPU families now stands at six. The new additions to the list include the Kaby Lake series that rolled out in 2017, the Skylake processors from 2014, the 2012-vintage Ivy Bridge and its immediate predecessor, Sandy Bridge. Intel said that it expects to share a beta version of a fixed patch with hardware makers by next week.

The chip is not the only company that has faced difficulties in addressing the CPU vulnerabilities. Shortly after issuing a Windows patch, Microsoft Corp. suspended the version released for machines with chips from Advanced Micro Systems Corp. due to reports of some computers becoming unusable. It completed the resolution process only yesterday.

The reason for these stumbles has to do with the nature of Spectre and Meltdown. The vulnerabilities are tied to a core feature called speculative execution that can be found in almost all processors produced over the past 20 years.

At a high level, the mechanism enables CPUs to make predictions about how certain code will run. This provides the ability to perform the necessary calculations ahead of time and thus speed up processing. Speculative execution is such a core element of modern processor design that Intel’s fix, which works by removing a firmware component used in the process, can incur a major cost even for users who don’t have to worry about potentially flawed patches.

The update can reportedly decrease performance by as much as 35 percent for computers running the worst-hit CPUs. Fortunately, the majority of users should only experience a considerably milder slowdown.

Photo: wiredforsound23/Flickr