Disabling multi-processing core in the system BIOS should disable all other "cores" in the processor, leaving one single core and thread available (this could vary according to BIOS implementation but that may depend on your Original Equipment Manufacturer).
In the other hand, disabling Hyper-Threading Technology does not mean that the physical core should double up its speed or performance. Performance differences when using a single core will depend on Intel® Turbo Boost Technology and this will be determined according to what the software running requires and power/heat headroom available.
You can use the Intel(R) Processor Identification Utility and Intel(R) processor diagnostic tool, available from:
You can even use a software like CPU-Z as a reference. For this you can check at: