31
Undocumented 8086 instructions, explained by the microcode
What happens if you give the Intel 8086 processor an instruction that doesn't exist? A modern microprocessor (80186 and later) will gener...
Ken Shirriff
Computer history, restoring vintage computers, IC reverse engineering, and whatever
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Visit righto.com → RSS feedOn Hacker News Jul 2013 – Oct 2026
Hardware & Electronics 171History & Retro Computing 128Systems & Performance 21Software Engineering 10Crypto & Blockchain 9Security & Privacy 7
32
Xerox Alto zero-day: cracking disk password protection on a 45 year old system
We've been archiving a bunch of old Xerox Alto disk packs from the 1970s. A few of them turned out to be password-protected, so I needed ...
33
Improvements to the Xerox Alto Mandelbrot drop runtime from 1 hour to 9 minutes
Last week I wrote a Mandelbrot set program for the Xerox Alto, which took an hour to generate the fractal. The point of this project was to...
34
Reverse engineering a counterfeit 7805 voltage regulator
Update: It turns out my 7805 isn't counterfeit. eclectro did an in-depth search ( details on reddit ) and found an old 7805 datasheet fro...
35
Apollo Guidance Computer switching power supply works after 50 years
We recently restored an Apollo Guidance Computer, the revolutionary computer that helped navigate to the Moon and land on its surface. 1 At...
36
Reverse-engineering the Intel 8086's instruction register
The Intel 8086 microprocessor is one of the most influential chips ever created; it led to the x86 architecture that dominates desktop an...
37
Inside the die of Intel's 8087 coprocessor chip, root of modern floating point
Looking inside the Intel 8087, an early floating point chip, I noticed an interesting feature on the die: the substrate bias generation circ...
38
Unusual circuits in the Intel 386's standard cell logic
I've been studying the standard cell circuitry in the Intel 386 processor recently. The 386, introduced in 1985, was Intel's most complex pr...
39
A look at the die of the 8086 processor
The Intel 8086 microprocessor was introduced 42 years ago this month, 1 so I made some high-res die photos of the chip to celebrate. The ...
40
Bitcoin mining on an Apollo Guidance Computer
We've been restoring an Apollo Guidance Computer 1 . Now that we have the world's only working AGC, I decided to write some code for it. Try...
41
Reverse-engineering a three-axis attitude indicator from the F-4 fighter plane
We recently received an attitude indicator for the F-4 fighter plane, an instrument that uses a rotating ball to show the aircraft's orienta...
42
Standard cells: Looking at individual gates in the Pentium processor
Intel released the powerful Pentium processor in 1993, a chip to "separate the really power-hungry folks from ordinary mortals." The origin...
43
Apple didn't revolutionize power supplies; new transistors did (2012)
The new biography Steve Jobs contains a remarkable claim about the power supply of the Apple II and its designer Rod Holt: [1] Instead o...
44
Hands-on with the PocketBeagle: a $25 Linux computer with lots of I/O pins
The PocketBeagle is a tiny but powerful inexpensive key-fob-sized open source Linux computer. It has 44 digital I/O pins, 8 analog input...
45
Reverse engineering the 76477 “Space Invaders” sound effect chip from die photos
Remember the old video game Space Invaders? Some of its sound effects were provided by a chip called the 76477 Complex Sound Generation ch...
46
Inside the vintage Xerox Alto's display, a tiny lightbulb keeps it working
In this Alto restoration episode, we repaired a second CRT display, exercising our TV repair skills and discovering a tiny mysterious lightb...
47
Iconic consoles of the IBM System/360 mainframes, 55 years old today
The IBM System/360 was a groundbreaking family of mainframe computers announced on April 7, 1964. Designing the System/360 was an extremely...
48
Yamaha DX7 chip reverse-engineering, part 4: how algorithms are implemented
The Yamaha DX7 digital synthesizer (1983) was the classic synthesizer in 1980s pop music. It uses two custom digital chips to generate sou...
49
Reverse-engineering Ethernet backoff on the Intel 82586 network chip's die
Introduced in 1973, Ethernet is the predominant way of wiring computers together. Chips were soon introduced to handle the low-level aspects...
50
Inside the digital clock from a Soyuz spacecraft
We recently obtained a clock that flew on a Soyuz space mission. 1 The clock, manufactured in 1984, is much more complex inside than you'd ...
51
The Globus INK: a mechanical navigation computer for Soviet spaceflight (2023)
The Soviet space program used completely different controls and instruments from American spacecraft. One of the most interesting navigati...
52
The transparent chip inside a vintage Hewlett-Packard floppy drive
While repairing an eight-inch HP floppy drive, we found that the problem was a broken interface chip. Since the chip was bad, I decapped it ...
53
TROS: IBM mainframes stored microcode in transformers
I recently came across a Transformer Read-Only Storage (TROS) module that stored microcode in an IBM System/360 mainframe computer. This unu...
54
A circuit board from the Saturn V rocket, reverse-engineered and explained
In the Apollo Moon missions, the Saturn V rocket was guided by an advanced onboard computer system built by IBM. This system was built fro...
55
The Intel 8088 processor's instruction prefetch circuitry: a look inside
In 1979, Intel introduced the 8088 microprocessor, a variant of the 16-bit 8086 processor. IBM's decision to use the 8088 processor in the I...
56
Notes on the Pentium's microcode circuitry
Most people think of machine instructions as the fundamental steps that a computer performs. However, many processors have another layer of ...
57
Tiny transformer inside: Decapping an isolated power transfer chip
I saw an ad for a tiny chip 1 that provides 5 volts 2 of isolated power: You feed 5 volts in one side, and get 5 volts out the other si...
58
Counting the transistors in the 8086 processor: it's harder than you might think
How many transistors are in Intel's 8086 processor? This seems like a straightforward question, but it doesn't have a straightforward answ...
59
Inside the Apollo “8-Ball” FDAI (Flight Director / Attitude Indicator)
During the Apollo flights to the Moon, the astronauts observed the spacecraft's orientation on a special instrument called the FDAI (Flight ...
60
Decoding an air conditioner control's checksum with differential cryptanalysis
Back in 2009 I wrote an Arduino library ( IRRemote ) to encode and decode infrared signals for remote controls. I got an email recently fr...