"Warm" vs "cold" start

Your IPL code may be quite simple or fairly elaborate, depending on how your embedded system is configured. We'll use the terms warm start and cold start to describe the different types of IPL:

Warm-start IPL
If there's a BIOS or ROM monitor already installed at the reset vector, then your IPL code is simply an extension to the BIOS or ROM monitor.
Cold-start IPL
The system doesn't have (or doesn't use) a BIOS or ROM monitor program. The IPL must be located at the reset vector.