As the engine Deep Sjeng supports HT, I assumed every engine can use it.

Only multiprocessor engines can.

But it seems it needs some additional code to use HT.

No (but it helps to have it).

I found this:

http://web.quick.cz/EVCOMP/evcpu.htm#HT

Bummer.

That page is a severe piece of misinformation.

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GCP