Dell 1750 and Xeon Hyper-Threading

Today I started to play with my new Dell servers. They are /so/ cool, although they are a bit noisy with all the fans blowing.

I’ve never had a Xeon machine before, and until today I thought hyper-threading was just some new Intel buzzword. Then 4 penguins appeared! A quick [!cat /proc/cpuinfo] revealed 4 CPUs, despite a previous visual inspection of the machine (and the invoice) detecting only 2.

So, it seems Intel have been quite smart. Instead of (or as well as) trying to make their instruction pipelines move faster, they are feeding two at a time into the Xeon. This wasn’t a new idea, but parallelism like this often required programs to know about it before they could use it. With /hyper-threading/ a single Xeon pretends that it is 2 different processors, and Linux already knows how to use extra processors.

When configuring and compiling Linux I discovered that I should enable ACPI to enumerate the processors correctly. I was going to enable it anyway, but I thought I should mention it in case you weren’t.

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