Bellmac 32
First 32-bit microprocessor to move 32 bits per clock cycle.
The Bellmac 32, also known as the WE 32000, is a 32-bit microprocessor developed by Bell Labs' processor division in 1980. It was the first microprocessor capable of moving 32 bits in one clock cycle, implemented using CMOS technology and containing 150,000 transistors. The design introduced a novel circuit technique called domino logic, which improved the speed of CMOS circuits.
- Year
- 1980
- Developer
- Bell Labs' processor division
- Technology
- CMOS
- Transistor count
- 150,000
- Clock speed
- 2 MHz (target 4 MHz)
- Data bus width
- 32 bits
- Number of registers
- 16 (32-bit)
Lore & Background
The Bellmac 32 was developed by AT&T engineers at three Bell Labs locations: Indian Hill, Holmdel, and Murray Hill. Lacking automation tools, designers used colored pencils for the initial design; later, Steve Law created a computer program to digitize the designs. The development produced domino logic, considered a breakthrough. Tests during manufacture suggested a clock frequency higher than the 4 MHz target was possible, but complications in implementing control logic limited the final speed to 2 MHz. The team considered it progress but not fully successful, as it did not meet AT&T's design goals.
Followup meetings led to the Bellmac 32A project, a second-generation version also using CMOS, with a target clock frequency of 6.2 MHz. Adjustments to maximize transistor and resistor sizes and minimize interconnections helped meet specifications. Engineers placed a 20-foot-by-20-foot engineering drawing of the chip layout on the floor of a large room. Testing of chips from the completed circuit exceeded the design speed, reaching 7, 8, and even 9 MHz. After the breakup of AT&T, Bell Labs became part of Western Electric, and the Bellmac 32 was renamed WE 32000. Updated versions included the WE 32100 (announced June 1984) and the WE 32200.
The architecture includes a pipelined design with an instruction fetch unit and an execution unit. It has 169 instructions optimized for the C programming language, with up to three operands. The processor lacks floating-point or decimal arithmetic instructions, which were later provided by coprocessors WE 32106 and WE 32206.
Reader's Guide
The Bellmac 32 holds significance as the first microprocessor to move 32 bits in a single clock cycle, marking a milestone in 32-bit computing. Its development at Bell Labs introduced domino logic, a circuit design technique that advanced CMOS speed. The processor was designed with the C programming language in mind, influencing its instruction set and memory addressing. The architecture provided conveniences for programming language implementers, including procedure linkage instructions and support for process management with dedicated call-process and return-to-process instructions. It supported four privilege levels and a controlled transfer mechanism for system calls and exception handling. The Bellmac 32's legacy includes the subsequent Bellmac 32A, which achieved higher clock speeds, and the renamed WE 32000 series, which continued with the WE 32100 and WE 32200. The project was eventually cancelled along with its successor, the Hobbit C-language Reduced Instruction Set Processor (CRISP).
Did You Know?
- The Bellmac 32 was the first microprocessor that could move 32 bits in one clock cycle.
- Its design introduced domino logic, a novel circuit technique considered a breakthrough for CMOS.
- The initial design was done with colored pencils due to a lack of automation tools.
- After the breakup of AT&T, the Bellmac 32 was renamed the WE 32000.
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