I've been reading What Every Programmer Should Know About Memory by U. Drepper, where they state the following on p. 3:
Red Hat, as of 2007, expects that for future products, the “standard building blocks” for most data centers will be a computer with up to four sockets, each filled with a quad core CPU that, in the case of Intel CPUs, will be hyper-threaded.2 This means the standard system in the data center will have up to 64 virtual processors.
2 Hyper-threading enables a single processor core to be used for two or more concurrent executions with just a little extra hardware.
What I'm unclear about is how such a system would have 64 (virtual) processors.
Let us even assume that a hyper-threaded CPU consists of 2 processors (I've read about this technology, so I know that it may even perform worse, and at most about 30% faster than a non-hyper-threaded CPU). A quad-core consists of 4 processors, so a device with 4 hyper-threaded quad-core CPUs would have 4 * 2 * 4 = 32 processors.
What am I missing?
