all contributing to faster single thread performance (from between 300% to 500% increase over previous generations. Additional effort was made to add the "critical thread API", where the operating system would detect a bottleneck and would temporarily allocate the resources of an entire core, instead of 1 (of 8) threads, to the targeted application processes exhibiting single threaded CPU bound behavior. This allowed the T4 to uniquely mitigate single threaded bottlenecks, while not having to compromise in the overall architecture to achieve massive multi-threaded throughput. Contemporary and subsequent designs The "Coolthreads(TM)" architecture, beginning with the UltraSPARC T1 (with its positive and negative aspects), was certainly influential in the concurrent and future designs of SPARC processors. "Rock" The original UltraSPARC T1 was designed for single CPU systems only and is not capable of SMP. "Rock" was a more ambitious project, intended to support multiple-chip server architectures, targeting traditional data-facing workloads such as databases. It was seen as more a follow-on to Sun's SMP processors such as UltraSPARC IV, rather than a replacement for the UltraSPARC T1 or T2, but was canceled in the timeframe of Oracle's acquisition of Sun. UltraSPARC T2 Formerly known by the codename Niagara 2, the follow-on to the UltraSPARC T1, the T2 provides eight cores. Unlike the T1, each core supports 8 threads per core, one FPU per core, one enhanced cryptographic unit per core, and CPU embedded 10 Gigabit Ethernet network controllers. UltraSPARC T2 Plus In February 2007, Sun announced at its annual analyst summit that its third-generation simultaneous multithreading design, code-named Victoria Falls, was taped out in October 2006. A two-socket server (2 RU) will have 128 threads, 16 cores, and a 65× performance improvement over UltraSPARC III. At the Hot Chips 19 conference, Sun announced that Victoria Falls will be in two-way and four-way servers. Thus, a single 4-way SMP server will support 256 concurrent hardware threads. In April 2008, Sun released 2-way UltraSPARC T2 Plus servers, the SPARC Enterprise T5140 and T5240. In October 2008, Sun released 4-way UltraSPARC T2 Plus SPARC Enterprise T5440 server. SPARC T3 In October 2006, Sun disclosed that Niagara 3 will be built with a 45 nm process. The Register, reported in June 2008 that the microprocessor will have 16 cores, incorrectly suggesting each core would have 16 threads. During the Hot Chips 21 conference Sun revealed the chip has a total of 16 cores and 128 threads.