trouble with HT

Garrett Cooper youshi10 at
Thu Apr 5 02:15:17 UTC 2007

Andrea Milani wrote:
> Jonathan Horne wrote:
>> well, wikipedia says this (something that i just now learned about 
>> standard pentium4 line of processors)
>> [wikipedia]
>> HyperThreading was present in all Northwood CPUs, but was disabled in 
>> the core in all but the 3.06 GHz model.
>> [/wikipedia]
> That's not true. I have a 2.6 GHz Northwood, and it supports 
> HyperThreading (however I'm not running FreeBSD on it, so I can't help 
> you with SMP).
> You can use the Intel Processor Spec Finder 
> ( to discover the capabilities of 
> your CPU, but I think the "HTT" that appears in the dmesg output 
> stands for Hyper Threading Technology.

As noted by Andrea, HTT has been available since 2.6GHz in the Northwood 
series (think 2.4GHz was the last non-HTT based Northwood CPU but I'd 
have to check some internal sources).

If you don't have SMP support setup on your freebsd box you need to 
either a) use the generic SMP kernel (it's called SMP, not GENERIC), or 
build a custom kernel with the following lines:

options SMP
device apic

Then you'll have a SMP enabled kernel :).

You also need to add: = 1
kern.smp.cpus = 1

to /etc/sysctl.conf. After you do that, you should see the following:

[root at hoover /home/gcooper]# dmesg | grep SMP
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
SMP: AP CPU #1 Launched!

Either Wikipedia's wrong, or you accidentally misread / misquoted that 


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