Webtagr - Technology News Summarizer

Apollo's '8-Ball': Dissecting the Lunar Module's Flight Director/Attitude Indicator

2025-06-14

This article delves into the Apollo lunar missions' Flight Director/Attitude Indicator (FDAI), a unique instrument featuring a rotating black ball nicknamed the '8-ball'. It meticulously explains the ingenious mechanism allowing the '8-ball' to rotate around three axes (roll, pitch, yaw), and the complex servo-control system within the FDAI, including synchros, servo loops, motor/tachometers, and amplifiers. The author traces the FDAI's history from its use in the X-15 rocket plane and F-4 fighter to its role in the Apollo lunar module and Space Shuttle simulator, highlighting its significance in aerospace history. Comparisons are drawn between the Apollo FDAI and the F-4's ARU/11-A indicator, revealing similarities and differences.

(www.righto.com)

Tech instrumentation

Reliving Smalltalk-76: Running the Legend on a Xerox Alto

2025-06-09

This blog post details the author's success in running Smalltalk-76 on a vintage Xerox Alto. Smalltalk, a pioneering object-oriented programming language, featured a groundbreaking GUI on the Alto, including the desktop metaphor, icons, scrollbars, and overlapping windows—influencing the design of the Apple Lisa and Macintosh. The article highlights Smalltalk's unique ability to view and modify system code while the system is running, demonstrated by modifying scrollbar code. Despite its slow speed, Smalltalk's implementation on the Alto holds significant historical and technical value, laying the groundwork for modern programming languages and GUI design.

(www.righto.com)

Tech

Archaeology of the Pentium's Microcode ROM

2025-03-31

This article delves into the low-level circuitry of the microcode ROM in the original Pentium processor. Using microscopic images of the chip die, the author reveals the ROM's physical structure: two rectangular banks of transistors, each providing 45 bits of output for a total 90-bit micro-instruction. The article meticulously details the functioning of the microcode address register, row select drivers, and output circuitry. It also explains the role of shift registers and XOR gates for testing purposes, and the complexity of power distribution within the Pentium. Ultimately, the author highlights the unexpected complexity of the Pentium's microcode ROM and the optimizations implemented for performance and density.

(www.righto.com)

Hardware

Revisiting 'The Mother of All Demos': Doug Engelbart and his 5-Key Keyset

2025-03-23

This article recounts Douglas Engelbart's groundbreaking 1968 computer demonstration, "The Mother of All Demos." It revisits the innovative technologies showcased, like the mouse and hypertext, but also delves into the lesser-known 5-key keyset and the author's experience interfacing it with a modern USB connection. Furthermore, the article clarifies the origin of the name, revealing it wasn't initially associated with Engelbart's demo but later adopted. A blend of technical details and historical narrative, the article offers a fascinating look at technological history and personal exploration.

(www.righto.com)

Tech Engelbart

The Pentium's Mysterious ×3 Circuit: A Deep Dive into Chip Design

2025-03-02

In 1993, Intel released the high-performance Pentium processor. This article delves into the surprisingly complex design of a seemingly simple circuit within the Pentium: the multiply-by-three circuit (×3 circuit). This circuit is part of the floating-point multiplier; the Pentium uses radix-8 multiplication, which is faster than binary multiplication, but multiplication by three requires special handling. The article explains how this circuit combines techniques like carry lookahead, Kogge-Stone adders, and carry-select adders to maximize performance. Analysis of microscope images of the chip reveals the intricate structure of the ×3 circuit and its crucial role in the Pentium, highlighting the ingenuity and technical innovation in processor design.

(www.righto.com)

Hardware processor design chip architecture radix-8 multiplication

The Surprisingly Complex History of the Word "Mainframe"

2025-02-01

This article delves into the unexpected evolution of the term "mainframe." Initially referring to the physical frames of early computers like the IBM 701, its meaning shifted over time. It became synonymous with the CPU, and eventually settled on its modern definition: a large, powerful computer for transaction processing or business applications. The article explores this semantic shift, analyzing the impact of minicomputers and microcomputers, IBM's role in popularizing the term, and its eventual widespread adoption.

(www.righto.com)

Tech mainframe technical terminology

Reverse-Engineering a Pentium's Clever BiCMOS Circuits

2025-01-21

This post details the reverse engineering of interesting BiCMOS circuits within Intel's Pentium processor, focusing on the output circuitry of the constant ROM in the floating-point unit. The author meticulously explains the layered structure, the use of MOS transistors, and the unique aspects of the BiCMOS driver. A deep dive into the multiplexers, latches, and driver design reveals the intricate design of the Pentium and highlights the role of BiCMOS technology in enhancing performance. The article ultimately illustrates the remarkable growth in processor complexity as described by Moore's Law.

(www.righto.com)

Hardware BiCMOS circuits

Reverse-Engineering a Pentium's Carry-Lookahead Adder

2025-01-18

Ken Shirriff's blog post details the reverse engineering of an 8-bit adder within the Pentium's floating-point unit. This adder, a Kogge-Stone carry-lookahead adder, accelerates addition by calculating carry bits in parallel. The post meticulously explains the carry-lookahead adder's principle, showcasing the Pentium's hardware implementation—a four-layer circuit structure employing the Kogge-Stone algorithm. It also discusses the adder's role in the Pentium's floating-point division unit and its connection to the infamous Pentium FDIV bug.

(www.righto.com)

Hardware carry-lookahead adder

It's Time to Ditch the Cargo Cult Metaphor: A Critique of Technological and Cultural Misunderstanding

2025-01-12

This article critiques the overuse of the 'cargo cult' metaphor in programming and technology. The author argues that the popular culture depiction of cargo cults is inaccurate and ignores the underlying colonial oppression and cultural destruction. Actual cargo cults are far more complex than simple imitation, blending religious, cultural, and responses to colonial history. The author calls for abandoning this misleading metaphor and acknowledging its historical and cultural significance.

(www.righto.com)

Tech cargo cult colonial history

Intel's Pentium FDIV Bug: A $475 Million Mistake

2024-12-28

In 1993, Intel launched the high-performance Pentium processor. A year later, a flaw in its floating-point division algorithm was discovered, causing incorrect results in rare cases. Initially dismissed by Intel, the bug—dubbed the FDIV bug—quickly gained media attention. The error stemmed from 16 missing entries in the processor's lookup table, with 5 entries directly causing incorrect calculations. Intel ultimately recalled and replaced all affected chips at a cost of $475 million. This article delves into the Pentium's division algorithm, pinpoints the bug's location on the chip, and explains the underlying mathematical error that led to this costly mistake.

(www.righto.com)

Hardware Pentium Hardware error