MAJC - Wikipedia
MAJC (Microprocessor Architecture for Java Computing) was a Sun Microsystems multi-core, multithreaded, very long instruction word (VLIW) microprocessor design from the mid-to-late 1990s. Originally called the UltraJava processor, the MAJC processor was targeted at running Java programs, whose "late compiling" allowed Sun to make several favourable design decisions. The processor was released into two commercial graphical cards from Sun. Lessons learned regarding multi-threads on a multi-core processor provided a basis for later OpenSPARC implementations such as the UltraSPARC T1.
Like other VLIW designs, notably Intel's IA-64 (Itanium), MAJC attempted to improve performance by moving several expensive operations out of the processor and into the related compilers. In general, VLIW designs attempt to eliminate the instruction scheduler, which often represents a relatively large amount of the overall processor's transistor budget. With this portion of the CPU removed to software, those transistors can be used for other purposes, often to add additional functional units to process more instructions at once, or to increase the amount of cache memory to reduce the amount of time spent waiting for data to arrive from the much slower main memory. Although MAJC shared these general concepts, it was unlike other VLIW designs, and processors in general, in a number of specific details.
Most processors include a number of separate "subprocessors" known as functional units that are tuned to operating on a particular type of data. For instance, a modern CPU typically has two or three functional units dedicated to processing integer data and logic instructions, known as ALUs, while other units handle floating-point numbers, the FPUs, or multimedia data, SIMD. MAJC instead used a single multi-purpose functional unit which could process any sort of data. In theory this approach meant that processing any one type of data would take longer, perhaps much longer, than processing the same data in a unit dedicated to that type of data. But on the other hand, these general-purpose units also meant that you did not end up with large portions of the CPU being unused because the program just happened to be doing many (for example) floating point calculations at that particular point in time.
