CPU set to compatible mode
Not every BIOS has this feature, but in some BIOSs, you can change the mode of the CPU from normal to compatible. You would use the compatible mode for troubleshooting because it drastically slows the system down.
If your system is being slow, boot to the BIOS and check to see if the CPU is in compatible mode. If it is, set it to Normal mode.
NOTE: Due to the various computer configurations available, BIOS layout is not available here. Please consult your manufacturer for help.