HyperThreading not working under 2.4.21

Hello there,

I recently tried to upgrade to the 2.4.21 vanilla kernel. I am using a Pentium IV 3,06ghz HT. Amongst other things, I enabled the following options:
"Pentium-4 processor Family, SMP support, ACPI support". I tried it with both ACPI support on and off. I can join a copy of my .config if it is required.

Anyway, when booting the 2.4.21 kernel my second logical processor is not detected at all. All works as if I had only one processor. There is no error message. A cat /proc/cpuinfo reports only one cpu.

This problem only occurs with 2.4.21 kernel. My HT processor was working perfectly with any branch of the 2.4.20 serie (I was using 2.4.20-ck6). My second logical processor was perfectly recognized. Thus, it does not seem to be a problem with bios or mb settings.

A "very" quick search through google made me conclude that this problem had not been reported yet so please, forgive me if you are all already aware of such a problem.

Best regards,

            R.C

P.S: join a copy to my e-mail adress if you may.