the hyper-threaded versions of the Intel Pentium 4 microprocessors, such as the "Northwood" and "Prescott". Modern commercial implementations The Intel Pentium 4 was the first modern desktop processor to implement simultaneous multithreading, starting from the 3.06 GHz model released in 2002, and since introduced into a number of their processors. Intel calls the functionality Hyper-Threading Technology, and provides a basic two-thread SMT engine. Intel claims up to a 30% speed improvement compared against an otherwise identical, non-SMT Pentium 4. The performance improvement seen is very application-dependent; however, when running two programs that require full attention of the processor it can actually seem like one or both of the programs slows down slightly when Hyper-threading is turned on. This is due to the replay system of the Pentium 4 tying up valuable execution resources, increasing contention for resources such as bandwidth, caches, TLBs, re-order buffer entries, and equalizing the processor resources between the two programs which adds a varying amount of execution time. The Pentium 4 Prescott core gained a replay queue, which reduces execution time needed for the replay system. This was enough to completely overcome that performance hit. The latest Imagination Technologies MIPS architecture designs include an SMT system known as "MIPS MT". MIPS MT provides for both heavyweight virtual processing elements and lighter-weight hardware microthreads. RMI, a Cupertino-based startup, is the first MIPS vendor to provide a processor SOC based on eight cores, each of which runs four threads. The threads can be run in fine-grain mode where a different thread can be executed each cycle. The threads can also be assigned priorities. Imagination Technologies MIPS CPUs have two SMT threads per core. IBM's Blue Gene/Q has 4-way SMT. The IBM POWER5, announced in May 2004, comes as either a dual core dual-chip module (DCM), or quad-core or oct-core multi-chip module (MCM), with each core including a two-thread SMT engine. IBM's implementation is more sophisticated than the previous ones, because it can assign a different priority to the various threads, is more fine-grained, and the SMT engine can be turned on and off dynamically, to better execute those workloads where an SMT processor would not increase performance. This is IBM's second implementation of generally available hardware multithreading. In 2010, IBM released systems based on the POWER7 processor with eight cores with each having four Simultaneous Intelligent Threads. This switches the threading mode between one thread, two threads or