The Cray-1: When Computers Were Furniture

• by Petabite
hardwarehistorysupercomputingarchitecture

The Cray-1: When Computers Were Furniture

The Cray-1 (1976) wasn’t just a computer—it was a statement. With its distinctive C-shaped design and bench seating, it looked more like modern art than a machine designed to perform 160 million floating-point operations per second.

Seymour Cray’s Vision

Seymour Cray understood something fundamental: at extreme speeds, physics matters more than logic. The Cray-1’s unusual design choices all served a single purpose—minimizing signal propagation time.

Design Innovations

Vector Processing: Instead of processing one number at a time, the Cray-1 could chain operations on entire arrays:

; Traditional approach (slow)
LOOP: LOAD R1, A[i]
      LOAD R2, B[i]
      ADD  R3, R1, R2
      STORE R3, C[i]
      INC i
      JUMP LOOP

; Vector approach (fast)
VLOAD  V1, A
VLOAD  V2, B
VADD   V3, V1, V2
VSTORE V3, C

Memory Architecture: Used the fastest SRAM available (ECL logic), organized into 16 banks to allow parallel access. Bandwidth was revolutionary for the era.

Cooling: Freon refrigeration kept the densely-packed electronics from melting. The system could dissipate 115 kilowatts—about as much as a small house.

The C-Shape Mystery

Why the distinctive C-shape? Wire length. Cray obsessed over shaving nanoseconds by minimizing the distance between CPU modules. The C-shape kept maximum wire length under 4 feet, limiting signal delay.

The bench? That’s where the power supplies lived. Also, it looked cool.

Legacy

Modern GPUs are spiritual successors to the Cray-1’s vector architecture. When you write CUDA code, you’re following principles Cray established 50 years ago:

  • Parallelism over clock speed
  • Memory bandwidth as the critical bottleneck
  • Special-purpose hardware for specific workloads

The Cray-1 taught us that sometimes the best way to go faster is to think differently about the problem.

By The Numbers

  • Price: $8.8 million (1976 dollars, ~$40M today)
  • Speed: 160 MFLOPS peak
  • Memory: 8 MB max (yes, megabytes)
  • Weight: 5.5 tons
  • Power: 115 kW
  • Units sold: ~80 systems

For context, an iPhone 15 Pro performs about 2,000,000 MFLOPS. We truly live in the future.