I am a little bit surprised with the following information that I get with dmidecode:
srs@ubuntu:~$ sudo dmidecode -t processor # dmidecode 2.9 SMBIOS 2.6 present. Handle 0x0004, DMI type 4, 42 bytes Processor Information Socket Designation: LGA1155 Type: Central Processor Family: <OUT OF SPEC> Manufacturer: Intel ID: A7 06 02 00 FF FB EB BF Version: Intel(R) Core(TM) i5-2500K CPU @ 3.30GHz Voltage: 1.0 V External Clock: 100 MHz Max Speed: 3800 MHz Current Speed: 3300 MHz Status: Populated, Enabled Upgrade: Other L1 Cache Handle: 0x0005 L2 Cache Handle: 0x0006 L3 Cache Handle: 0x0007 Serial Number: To Be Filled By O.E.M. Asset Tag: To Be Filled By O.E.M. Part Number: To Be Filled By O.E.M. Core Count: 4 Core Enabled: 1 Characteristics: 64-bit capable
However from gnome-system-monitor I can see 4 CPU working at the same time.