Just got an AMD Athlon x4 750 and after booting it up it only shows two cores when I know for a fact that it has 4. I have Windows 10 if that helps.
Edit: FOUND A FIX: Go to msconfig --> boot --> advanced options --> uncheck number of processors, reboot pc, go back into msconfig, boot, etc, then the number of cores you have should show up. Click the number you have, then reboot.
Edit: FOUND A FIX: Go to msconfig --> boot --> advanced options --> uncheck number of processors, reboot pc, go back into msconfig, boot, etc, then the number of cores you have should show up. Click the number you have, then reboot.