I have an intel core 2 duo with hyper threading capabilities (cat /proc/cpuinfo shows ht), but can't enable it.

I have recompiled the kernel(2.6.29.2) with Symmetric multi-processing support, set the maximum number of cpu's to 4, enabled SMT hyperthreading scheduler support,also enabled multi-core scheduler support and set processor family to Core 2/Newer Xeon.But when i check /proc/cpuinfo it only shows 2 cpu's (it should show 4 - 2 physical's + 2 logical's).

Do i need to keep the maximum number of cpu's as 4, or 2 is sufficient?In other words, the maximum number of cpu's refer only to physical or physical+logical?

Is there any command line option to activate Hyper threading? In my BIOS there is not option to enable hyper threading(my BIOS setup screen pratically only shows boot order options).

I have tried setting as kernel boot command line ht=on, but to no avail.

I am running Slackware 12.2 and my cpu is an Intel(R) Pentium(R) Dual CPU T2310 @ 1.46GHz.

Just to make things clear...
Do you physically have two processors on your motherboard, both Core2 Duo?

Your cpu does not do hyperthreading. It has two cores, but they are not hyperthreading-capable.

Hyperthreading returned to the Intel line with the nehalem series, and this device is in no way as powerful as the nehalems. It was previously available in the old (hot and power-hungry) Pentium Ds and it isn't one of those, either.

I'm not quite sure why cpuinfo shows it as 'ht', but I suspect if two threads are created, they are just shared around the cores, so it probably isn't a disadvantage.

The fundamental point is your cpu is not only incapable of it, but you can't upgrade to one of the current hyperthreading-capable cpus, as they are not compatible with your socket, as the newer ones have a revised socket to cope with the new memory interface.