X704

The X704 (stylized as X704) is a microprocessor developed by Exponential Technology that implements the 32-bit version of the PowerPC (ISA).

Description
The X704 was a microprocessor that issued up to three instructions per cycle to an  (ALU), floating-point unit (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 were direct-mapped. The L2 cache was on-die and was 32 KB large. It is eight-way set set-associative. The L3 cache was larger, supporting capacities of 512 KB to 2 MB, and was located externally. The x704 contained 2.7 million transistors, of which 0.7 million were and 2.0 million were  (MOS), and measured 15 mm by 10 mm (150 mm2). It was fabricated in a 0.5 µm process with six levels of interconnect. It used 3.6 and 2.1 V power supplies and dissipated less than 85 W at 533 MHz. The x704 was packaged in a 356-ball (BGA).

History
The X704 microprocessor was notable for its high clock frequency (for the time in 1996) in the range of 410 to 533 MHz, its use of s for logic and circuits for memory. However, it was never used in a shipping product by Apple Computer or any Macintosh clone manufacturer. Exponential Technology eventually failed as a result of the lack of business, but some of its former employees founded Intrinsity, a start-up that developed a high clock frequency implementation, FastMATH. The company was acquired by Apple and licensed Fast14 to third parties such as ATI Technologies for their GPUs.

Articles

 * Exponential unveils world's fastest PC microprocessor at 533MHz at The CPU Shack (1996-10-21)
 * The Exponential x704: A 533MHz BiCMOS PowerPC for the Desktop by Jay Pattin, Exponential at Stanford University (1996-11-06)
 * A 533-MHz BiCMOS superscalar RISC microprocessor at IEEE Journal of Solid-State Circuits (1997-11)