What is hyper threading?

Many processors have a technology on board known as hyperthreading. It ensures faster operation of the CPU, but you would rather not want it these days. How about that?

Hyperthreading made its appearance with the Pentium 4 in 2000, so a long time ago. Simply put, it is a trick to put unused parts of the processor core to work while executing an instruction. By having other instructions processed in advance. Provided the operating system is adapted for hyperthreading, which was quite a problem in the early days. This led to sometimes even slower rather than faster computers.

Later the trick worked very nicely. After all, you can also have another processed at the same time as an instruction. Sometimes things go wrong and that second instruction turns out not to be necessary after all and it is dumped. In general, according to Intel, the trick ultimately yields about 30% speed gain. Note that we are now talking about the early generation of hyperthreading processors. They only contain one real CPU core, so any acceleration that could realize some form of parallel processing was a nice improvement. Later it became technically easier to place multiple CPU cores (where CPU stands for Central Processing Unit; in good Dutch processor) on one chip. Yet you also see there that hyperthreading is still used; simply to make each of these cores faster. You can also think of hyperthreading as a kind of virtual processor. The operating system usually sees them simply as 'separate' processors.

Future without hyperthreading

Yet the future does not lie in hyperthreading. In fact, Intel nowadays recommends turning off the entire hyperthreading (if possible). The reason is simple: it is an older technique that does not appear to be safe at all. Hackers can extract data by messing around with hyperthreading. Specter and Meltdown are the best-known examples of hacks around the technology. And unfortunately there are now more such hacks in circulation. Intel is therefore slowly saying goodbye to risky hyperthreading. More CPU cores is a safer solution that is also easy and, above all, cheaper to realize these days. Still, you'll be dealing with the legacy of hyperthreading for a while yet. Many relatively recent processors (and therefore computers) have the technology on board.

Because replacing laptops and PCs is much slower than in the past, hyperthreading will also be around for a while. So make sure your system is up to date by installing updates regularly. Incidentally, the chance that you as a home user will really have to deal with Specter, Meltdown and the like is not very large. It is mainly data centers that get into trouble. Because they are attractive targets for hackers, patches there against the hacks cause significant speed losses. And that in turn leads to rising energy costs, slower servers, and so on. Disabling hyperthreading there definitely has a huge impact!

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