The x704 is a 32-bit

PowerPC PowerPC (with the backronym Performance Optimization With Enhanced RISC – Performance Computing, sometimes abbreviated as PPC) is a reduced instruction set computer (RISC) instruction set architecture (ISA) created by the 1991 Apple Inc., App ...

microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

developed in 1997 by

Exponential Technology Exponential Technology (originally Renaissance Microsystems) was a vendor of PowerPC microprocessors. The company was founded by George Taylor and Jim Blomgren in 1993. The company's plan was to use BiCMOS technology to produce very fast processors ...

. The microprocessor was notable for its high clock frequency in the range of 400 to 533 MHz, its use of

bipolar transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor (FET), uses only one kind of charge carrier. A ...

s for logic and

CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss ", , ) is a type of MOSFET, metal–oxide–semiconductor field-effect transistor (MOSFET) semiconductor device fabrication, fabrication process that uses complementary an ...

circuits for memory, and its failure to see use in an

Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

Macintosh Mac is a brand of personal computers designed and marketed by Apple Inc., Apple since 1984. The name is short for Macintosh (its official name until 1999), a reference to the McIntosh (apple), McIntosh apple. The current product lineup inclu ...

, the opposite of what industry observers such as '' Microprocessor Report'' had expected. Exponential Technology eventually failed as a result of the x704's lack of success, but some of its former employees founded Intrinsity, a start-up that developed a high clock frequency MIPS implementation, FastMATH. Incidentally, Intrinsity was acquired by Apple in 2010 to aid in the development of their line of ARM microprocessors. The x704 is a

superscalar A superscalar processor (or multiple-issue processor) is a CPU that implements a form of parallelism called instruction-level parallelism within a single processor. In contrast to a scalar processor, which can execute at most one single in ...

microprocessor that issues up to three instructions per cycle to an

arithmetic logic unit In computing, an arithmetic logic unit (ALU) is a Combinational logic, combinational digital circuit that performs arithmetic and bitwise operations on integer binary numbers. This is in contrast to a floating-point unit (FPU), which operates on ...

(ALU),

floating-point unit A floating-point unit (FPU), numeric processing unit (NPU), colloquially math coprocessor, is a part of a computer system specially designed to carry out operations on floating-point numbers. Typical operations are addition, subtraction, multip ...

(FPU) and branch unit. To realize the short cycle times, the caches were kept small, limiting its performance. There are three levels of cache. The first consisted of separate 2 KB instruction and data caches. These are direct-mapped. The L2 cache is on-die and is 32 KB in size. It is eight-way set set-associative. The L3 cache is larger, supporting capacities of 512 KB to 2 MB, and is located externally. The x704 contained 2.7 million transistors, of which 0.7 million were

bipolar transistors A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor (FET), uses only one kind of charge carrier. A ...

and 2.0 million were metal oxide semiconductor (MOS), and measured 15 mm by 10 mm (150 mm²). It was fabricated in a 0.5 μm

BiCMOS Bipolar CMOS (BiCMOS) is a semiconductor technology that integrates two semiconductor technologies, those of the bipolar junction transistor and the CMOS (complementary metal–oxide–semiconductor) logic gate, into a single integrated circuit. ...

process with six levels of interconnect. It uses 3.6 and 2.1 V power supplies and dissipates less than 85 W at 533 MHz. The x704 is packaged in a 356-ball ball grid array (BGA).

References

* * * {{Electron-stub PowerPC microprocessors