X704
Encyclopedia
The x704 is a microprocessor
that implements the 32-bit version of the PowerPC
instruction set architecture (ISA) developed by Exponential Technology
. The microprocessor was notable for its high clock frequency (for the time, circa 1997) in the range of 400 to 533 MHz, its use of bipolar transistor
s for logic and CMOS
circuits for memory, and its failure to see use in an Apple Macintosh, the opposite of what industry observers such as Microprocessor Report expected. Exponential Technology eventually failed as a result of the x704's lack of success, but its former employees founded Intrinsity
, a start-up that developed a high clock frequency MIPS
implementation, FastMath. The company has now left the microprocessor business and licenses Fast14 dynamic logic
to third-parties such as ATI
for their GPUs.
The x704 was a superscalar
microprocessor that issued up to three instructions per cycle to an arithmetic logic unit
(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 bipolar transistors
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
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 ball grid array
(BGA).
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
that implements the 32-bit version of the PowerPC
PowerPC
PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
instruction set architecture (ISA) developed by Exponential Technology
Exponential Technology
Exponential Technology 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 for the Apple Computer market. Logic used 3-level ECL circuits while RAM structures...
. The microprocessor was notable for its high clock frequency (for the time, circa 1997) in the range of 400 to 533 MHz, its use of bipolar transistor
Bipolar junction transistor
|- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...
s for logic and CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
circuits for memory, and its failure to see use in an Apple Macintosh, the opposite of what industry observers such as Microprocessor Report expected. Exponential Technology eventually failed as a result of the x704's lack of success, but its former employees founded Intrinsity
Intrinsity
Intrinsity was a privately held Austin, Texas based fabless semiconductor company; it was founded in 1997 as EVSX on the remnants of Exponential Technology and changed its name to Intrinsity in 2000...
, a start-up that developed a high clock frequency MIPS
MIPS architecture
MIPS is a reduced instruction set computer instruction set architecture developed by MIPS Technologies . The early MIPS architectures were 32-bit, and later versions were 64-bit...
implementation, FastMath. The company has now left the microprocessor business and licenses Fast14 dynamic logic
Dynamic logic (digital logic)
In integrated circuit design, dynamic logic is a design methodology in combinatorial logic circuits, particularly those implemented in MOS technology. It is distinguished from the so-called static logic by exploiting temporary storage of information in stray and gate capacitances...
to third-parties such as ATI
Ati
As a word, Ati may refer to:* Ati, a town in Chad* Ati, a Negrito ethnic group in the Philippines* Ati-Atihan Festival, an annual celebration held in the Philippines* Ati, a queen of the fabled Land of Punt in Africa...
for their GPUs.
The x704 was a superscalar
Superscalar
A superscalar CPU architecture implements a form of parallelism called instruction level parallelism within a single processor. It therefore allows faster CPU throughput than would otherwise be possible at a given clock rate...
microprocessor that issued up to three instructions per cycle to an arithmetic logic unit
Arithmetic logic unit
In computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations.The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...
(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 bipolar transistors
Bipolar junction transistor
|- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...
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
BiCMOS
BiCMOS is an evolved semiconductor technology that integrates two formerly separate semiconductor technologies - those of the analog bipolar junction transistor and the digital CMOS transistor - in a single integrated circuit device....
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 ball grid array
Ball grid array
A ball grid array is a type of surface-mount packaging used for integrated circuits.- Description :The BGA is descended from the pin grid array , which is a package with one face covered with pins in a grid pattern. These pins conduct electrical signals from the integrated circuit to the printed...
(BGA).