Introduction Gaisler Research provides synthesisable processor cores based on the SPARC V8 architecture. The cores are highly configurable, and particularly suitable for system-on-a-chip (SOC) designs. The LEON2 processor was designed under contract from the European Space Agency. It exists in two versions: standard and fault-tolerant. The fault-tolerant version of LEON2 is aimed for critical space applications, available as a radiation-hardened component from Atmel. The standard version of LEON2 is made freely available in full source code under the GNU LGPL license. It has successfully been used in many research and commercial applications. LEON3 is a new implementation of the SPARC V8 arcitecture, with an improved pipeline and multi-processor support. It is available in full source code under the GNU GPL license, as part of the GRLIB IP library. A fault-tolerant verion of LEON3 will be available in Q1 2005, suitable for both ASIC design as well as radiation-hardened Actel RTAX FPGAs.