CT Scan Reveals Six Layers of Hidden Wiring in 1985 Intel 386 Processor Package

Cambridge, MA – A recent computed tomography (CT) scan of an Intel 386 processor from the mid-1980s has uncovered previously unmapped internal complexities, including six layers of intricate wiring and an unexpected manufacturing step. The scan, performed by industrial CT scanning company Lumafield for renowned reverse engineer Ken Shirriff, provides the first public mapping of the processor's ceramic package. As Jon Bruner, Lumafield's Director of Marketing, stated in a tweet, "This is a CT scan of an Intel 386 processor from the mid-1980s that we ran for @kenshirriff! He used it to produce the first ever public mapping of the package, and he discovered an interesting manufacturing step along the way."

The Intel 386, launched in 1985, was a pivotal microprocessor, marking the x86 architecture's transition to 32-bit computing. Its 132-pin ceramic package was custom-designed by Intel to meet high pin count, thermal, and low-noise power requirements, effectively acting as a miniature six-layer printed circuit board. This advanced packaging was crucial for the chip's performance, contrasting with earlier Intel processors that suffered from inadequate packaging.

Lumafield, a company specializing in accessible industrial CT scanning, utilizes technology that captures hundreds of X-ray images from various angles to create detailed 3D reconstructions. Their Neptune CT scanner and Voyager analysis software allow engineers to non-destructively inspect internal structures, a significant advancement over traditional methods like cutting parts. This capability enabled the detailed examination of the 386's internal architecture without damaging the historical artifact.

The CT scan revealed surprising details, including nearly invisible metal wires extending to the sides of the package, which Shirriff identified as contacts used during the electroplating process for the gold pins. Additionally, the scan showed that the 386 utilized two separate power and ground networks—one for I/O and another for the CPU's logic—a design choice aimed at mitigating power spikes and ensuring stable operation. This dual power network was not explicitly detailed in the original 386 datasheets.

Ken Shirriff, known for his extensive work in reverse engineering vintage electronics and microprocessors, collaborated with Lumafield to conduct this analysis. His previous projects include detailed examinations of components within the Intel Pentium and Apollo-era hardware. This latest endeavor adds to his comprehensive body of work, offering unprecedented insights into the manufacturing and design intricacies of early 32-bit processors. The findings underscore the hidden complexities within seemingly simple components and highlight the continuous evolution of chip packaging technology.