There is disclosed in one example a multi-core computing system configured to provide a hot-swappable CPU0, including: a first CPU in a first CPU socket and a second CPU in a second CPU socket; a switch including a first media interface to the first CPU socket and a second media interface to the second CPU socket; and one or more mediums including non-transitory instructions to detect a hot swap event of the first CPU, designate the second CPU as CPU0, determine that a new CPU has replaced the first CPU, operate the switch to communicatively couple the new CPU to a backup initialization code store via the first media interface, initialize the new CPU, and designate the new CPU as CPUN, wherein N≠0.