Trap architectures for Lisp systems

Recent measurements of Lisp systems show a dramatic skewing of operation frequency. For example, small integer (fix-num) arithmetic dominates most programs, but other number types can occur on almost any operation. Likewise, few memory references trigger special handling for garbage collection, but nearly all memory operations could trigger such special handling. Systems like SPARC and SPUR have shown that small amounts of special hardware can significantly reduce the need for inline software checks by trapping when an unusual condition is detected.