Ypsilon

Ypsilon is the implementation of Scheme Programming Language, which conforms to the latest standard R6RS. It achieves a remarkably short GC pause time and the best performance in parallel execution as it implements "mostly concurrent garbage collection", which is optimized for the multi-core CPU system.

http://code.google.com/p/ypsilon/

Implementing SRFIs: SRFI-1 SRFI-13 SRFI-14 SRFI-19 SRFI-26 SRFI-27 SRFI-28 SRFI-38 SRFI-39 SRFI-41 SRFI-42 SRFI-48 SRFI-6 SRFI-8 SRFI-9 SRFI-98