A processing system with multiple processing units may support separate operating systems (OSs) in separate partitions. During an initialization process, a preboot manager in the processing system may copy software to a sequestered area of memory in the processing system. The preboot manager may also configure the processing system to hide the sequestered area of memory from a first partition of the processing system. Also, the preboot manager may use a first processing unit in the processing system to boot an OS on the first partition, and the preboot manager may transmit a boot trigger from the first processing unit to a second processing unit in the processing system. The boot trigger may cause the second processing unit to use the software in the sequestered area of memory to boot a second partition of the processing system. Other embodiments are described and claimed.