Rigel was a

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circ ...

chip set developed and fabricated by

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president un ...

(DEC) that implemented the VAX instruction set architecture (ISA). It was introduced on 11 July 1989 with the introduction of the VAX 6000 Model 400, the first system to feature the chip set. Rigel was also used in the VAX 4000 Model 300 and

VAXstation The VAXstation is a discontinued family of workstation computers developed and manufactured by Digital Equipment Corporation using processors implementing the VAX instruction set architecture. VAXstation systems were typically shipped with eithe ...

3100 Model 76. Production Rigel CPUs were rated at 35 to 43 MHz. The Rigel chipset consisted of several devices: *REX520

central processing unit A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...

(also known as the DC520 or "P-chip") *DC523

floating-point unit In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be ...

(codenamed ''KIWI'' or "F-chip" during development) *DC592 cache controller (codenamed ''COW'' or "C-chip" during development) *DC521 clock chip In addition, two further devices implemented the VAX

vector processor In computing, a vector processor or array processor is a central processing unit (CPU) that implements an instruction set where its instructions are designed to operate efficiently and effectively on large one-dimensional arrays of data calle ...

option; these comprised the DC555 Vector Register set chip (''VERSE'') and the DC556 Vector Data Path chip (''FAVOR''). Support chips for Rigel-based systems included the RSSC (Rigel System Support Chip) and ''Ghidra'', the VAX 4000 system interface chip.

REX520

The Rigel architecture was based on the VAX 8800 processor. It has a six-stage microinstruction pipeline and 64-entry fully associative translation look-aside buffer. The Rigel chip set supported an optional

and the REX520 decoded any vector instructions and passed on to the vector interface (VC) chip by the REX520. The REX520 has a 2 KB unified primary cache, configurable as an instruction cache and an external 128 KB secondary cache (backup cache) implemented with CMOS

static random access memory Static random-access memory (static RAM or SRAM) is a type of random-access memory (RAM) that uses latching circuitry (flip-flop) to store each bit. SRAM is volatile memory; data is lost when power is removed. The term ''static'' differ ...

(SRAM) chips. The REX520 has an external cache because the VAX 8800's 64 KB primary cache could not be integrated on the same die. The backup cache controller was located on the VC chip. The REX520 consisted of 320,000 transistors, of which 140,000 are for logic and 180,000 for memory. The die measures 12 mm by 12 mm (144 mm²). It was packaged in a 224-lead ceramic leaded package.

Fabrication

The chip set was fabricated by DEC in their second-generation

complementary metal–oxide–semiconductor Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSF ...

(CMOS) process, CMOS-2. The process had a 1.5 µm minimum feature size and two levels of

aluminium interconnect In integrated circuits (ICs), interconnects are structures that connect two or more circuit elements (such as transistors) together electrically. The design and layout of interconnects on an IC is vital to its proper function, performance, power ef ...

Mariah

Mariah was a revised version of the Rigel chip set fabricated by DEC in their 1 µm CMOS-3 process, with higher clock frequencies between 55 and 71 MHz. The Mariah CPU, FPU and cache controller were designated DC595, DC596 and DC597 respectively. Enhancements over Rigel included a 4 kB first-level cache and 32-bit physical memory addressing in the Mariah CPU, and write-back caching implemented in the cache controller chip. Mariah was used in the VAX 6000 Model 500, MicroVAX 3100 Model 80 and VAXstation 4000 Model 60.

References

"Rigel" at The Computer History Simulation Project

* Durdan, W. Hugh et al. (1990). "An Overview of the VAX 6000 Model 400 Chip Set". ''Digital Technical Journal'', Volume 2, Number 2, 1990. pp. 36–51. * Slater, Debra L. et al. (1990). "Vector Processing on the VAXvector 6000 Model 400". ''Digital Technical Journal'', Volume 2, Number 2, 1990. pp. 11–26. {{Digital Equipment Corporation DEC microprocessors 32-bit microprocessors