righto-com

A reverse-engineering analysis of an ALU board from the Mitra 125 MS minicomputer used in Spacelab. The 16-bit computer lacked a microprocessor, using TTL chips like the 74181 ALU. The article also covers the French computer industry's history, the Plan Calcul, and Spacelab's eventual upgrade to IBM AP-101SL computers.

The article argues against using the "cargo cult" metaphor popularized by Richard Feynman, stating it's based on inaccurate pop-culture depictions. It explains that real cargo cults were diverse religious movements in Melanesia, often reactions to colonial oppression, not simply people mimicking runways expecting planes.

The article reverse-engineers an 8-bit carry-lookahead adder in the Pentium's floating point unit, identifying it as a Kogge-Stone parallel prefix adder. This specialized adder computes carries in parallel to speed up division operations and was involved in the Pentium FDIV bug.

A reverse-engineering analysis reveals the BiCMOS circuits used in Intel's 1993 Pentium processor, specifically examining the multiplexer/driver circuits that output data from the floating-point unit's constant ROM. The article details how these circuits combine bipolar transistors with CMOS logic to drive signals across the chip.

The term "mainframe" originated with the IBM 701 computer in 1952, where "main frame" referred to the primary physical box of the system. The word's meaning evolved from describing a computer's physical cabinet to becoming synonymous with the central processing unit. By the 1970s, it began to denote large, powerful computers for business applications, a definition that solidified over decades.

The Pentium processor contains a specialized circuit to multiply by three, which is part of its floating-point multiplier. This complex circuit uses advanced digital design techniques to ensure high speed, as it's critical for the processor's base-8 multiplication approach.

A USB interface was created for Douglas Engelbart's 1960s keyset, a five-finger chorded input device from his groundbreaking "Mother of All Demos" presentation. The keyset, unlike Engelbart's other innovations like the mouse and hypertext, never gained widespread adoption.

The Pentium processor uses microcode stored in a ROM to execute machine instructions. The microcode ROM consists of two banks that output 90-bit micro-instructions, containing 4608 instructions total. The ROM's output lines travel across the chip to control various circuitry.

A vintage Commodore PET computer was repaired after extensive troubleshooting revealed multiple faulty chips. The restoration required replacing two failed ROM chips and four bad RAM chips, with one ROM adapter board initially causing issues due to under-powered programming. Using tools like a logic analyzer and Retro Chip Tester helped diagnose the problems in the 1977 home computer.

The Intel 386 processor implements its 30 registers using six different specialized circuits, each optimized for specific access patterns. These include triple-ported registers for simultaneous reads and writes, double-density layouts, and circuits supporting 8, 16, or 32-bit accesses.

The article reverse engineers the Intel 386 processor's prefetch queue circuitry, which fetches instructions before execution to improve performance. It examines the incrementer's Manchester carry chain and carry skip techniques, the alignment network for byte rotation, and the limit check circuit that prevents prefetching beyond memory segments.

The Apollo FDAI (Flight Director/Attitude Indicator), nicknamed the "8-ball," displayed spacecraft orientation using a rotating ball and provided flight guidance with needles. The mechanism uses three motors and slip rings to achieve three-axis rotation through a servo loop system.

Researchers reverse-engineered a Motorola-built Up-Data Link Confidence Test Set from the Apollo era, which was used to test the spacecraft's digital command system. The undocumented device used thumb-sized encapsulated modules containing logic gates, flip-flops, and other components, requiring extensive analysis to understand its functionality.

The article details the reverse engineering process of the Philips TDA7000, the first FM radio receiver chip from 1977. It examines the chip's components visible in die photos, including NPN and PNP transistors, resistors, and capacitors. The analysis explains common analog circuits like differential amplifiers and current mirrors used in the design.

A CT scan of Intel's 386 processor reveals six layers of complex wiring inside its ceramic package, including nearly invisible side wires for electroplating. The scan also shows the chip has two separate power and ground networks: one for I/O circuitry and another for the CPU's logic.

The article examines how the Intel 386 processor's I/O circuitry protects against three major threats: static electricity through protection diodes, latchup via guard rings, and metastability using synchronizers. These specialized circuits differ from the chip's internal logic and safeguard the processor from external dangers that could cause damage or malfunctions.

A Science paper and several other publications have incorrectly cited the compound Cr2Gr2Te6, which does not exist. The correct compound is Cr2Ge2Te6 (chromium germanium telluride), with Ge representing germanium. This typographical error has been copied across multiple scientific papers and a book chapter.

Diné weaver Marilou Schultz created a wool rug depicting the internal circuitry of the 555 timer integrated circuit. The weaving shows the chip's metal wiring as white lines on a black background with reddish-orange diamonds representing bond pads. Schultz has been creating chip-inspired weavings since 1994, using traditional Navajo-Churro wool and metallic threads.

The author describes using the MiniZinc constraint solver to solve the New York Times Pips puzzle, where dominoes must be placed on a grid under specific conditions. They explain how to express the puzzle constraints in MiniZinc and report that the solver found solutions in milliseconds.

The Intel 386 processor used standard cell logic to manage its complexity, employing automated place-and-route techniques. Analysis reveals unusual circuits including large multiplexers built from CMOS switches, a single transistor placed outside standard cell columns, and cells that appear to be inverters but function as independent transistors.

Intel's 8087 floating-point coprocessor, introduced in 1980, performed operations up to 100 times faster than early microprocessors. The chip's eight registers are organized in a stack architecture, with control circuitry managing push/pop operations and relative register access.

The Intel 8087 floating-point coprocessor uses 49 different conditional tests in its microcode to control jumps and subroutine calls. These conditions range from simple checks like whether a number is zero to specialized tests for rounding direction or instruction opcode bits. The selection circuitry uses a distributed tree of multiplexers across the chip to efficiently route condition signals.

The Intel 8086 processor's arithmetic-logic unit performs 28 operations on 16-bit values. Its control circuitry translates microcode instructions into ALU control signals, requiring separate micro-instructions to configure operations and retrieve results.

The Intel 8087 floating-point coprocessor chip added 62 instructions to IBM PCs in the 1980s. It uses multiple decoding techniques including PLAs and microcode to interpret instructions, with the 8086 computing memory addresses for the 8087 to use.

IBM's System/4 Pi family of aerospace computers, introduced around 1967, were used in military aircraft, missiles, and spacecraft including the Space Shuttle and Skylab. The compact, powerful computers controlled critical systems like navigation, weapons delivery, and spacecraft orientation. Models included the TC tactical computer, CP customized processor, and EP extended performance variants.

The B-52 bomber's star tracker system used an electromechanical analog computer called the Angle Computer to perform trigonometric calculations for celestial navigation. This complex device physically modeled the celestial sphere to compute star positions, providing navigation data before GPS technology existed.