Executes a single thread until it reaches a situation that triggers a context switch.
Typical switching event: the instruction execution reaches a long-latency operation or a situation where a latency may arise.
Compared to the cycle-by-cycle interleaving technique, a smaller number of threads is needed
A single thread can execute at full speed until the next context switch.
Single thread performance is similar to the performance of a comparable processor without multithreading.
? IBM NorthStar processors are two-threaded 64 bit PowerPCs with switch-on-cache-miss; implemented in departmental computers (eServers) of IBM since 10/98! (revealed at MTEAC-4, Dec. 2000)
Recent announcement (Oct. 1999): Sun MAJC5200 two processor on a die, each processor is a 4-threaded block-interleaving VLIW