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Computer history, restoring vintage computers, IC reverse engineering, and whatever The Apollo missions to the Moon required complex hardware to communicate between Earth and the spacecraft, sending radio signals over hundreds of thousands of miles. The premodulation processor was a key component of this system, combining voice, scientific data, TV, and telemetry for transmission to Earth.1 It was
Computer history, restoring vintage computers, IC reverse engineering, and whatever The Yamaha DX7 synthesizer's clever exponential circuit, reverse-engineered The Yamaha DX7 digital synthesizer was released in 1983 and became extremely popular, defining the sound of 1980s pop music. Because microprocessors weren't fast enough in the early 1980s, the DX7 used two custom digital chips: the EGS "env
Computer history, restoring vintage computers, IC reverse engineering, and whatever The Yamaha DX7 digital synthesizer was released in 1983 and became "one of the most important advances in the history of modern popular music"1. It defined the sound of 1980s pop music, used by bands from A-ha and Michael Jackson to Dolly Parton and Whitney Houston. The DX7's electric piano sound can be heard in ov
Computer history, restoring vintage computers, IC reverse engineering, and whatever The Intel 8086 processor was introduced in 1978, setting the course of modern computing. While the x86 processor family has supported 64-bit processing for decades, the original 8086 was a 16-bit processor. As such, it has a 16-bit arithmetic logic unit (ALU).1 The arithmetic logic unit is the heart of a processor:
Computer history, restoring vintage computers, IC reverse engineering, and whatever We've been restoring an Apollo Guidance Computer1. Now that we have the world's only working AGC, I decided to write some code for it. Trying to mine Bitcoin on this 1960s computer seemed both pointless and anachronistic, so I had to give it a shot. Implementing the Bitcoin hash algorithm in assembly code on this 1
Computer history, restoring vintage computers, IC reverse engineering, and whatever I recently started FPGA programming and figured it would be fun to use an FPGA to implement the FizzBuzz algorithm. An FPGA (Field-Programmable Gate Array) is an interesting chip that you can program to implement arbitrary digital logic. This lets you build a complex digital circuit without wiring up individual gat
Computer history, restoring vintage computers, IC reverse engineering, and whatever We succeeded in running the Smalltalk-76 language on our vintage Xerox Alto; this blog post gives a quick overview of the Smalltalk environment. One unusual feature of Smalltalk is you can view and modify the system's code while the system is running. I demonstrate this by modifying the scrollbar code on a running
Computer history, restoring vintage computers, IC reverse engineering, and whatever A computer's arithmetic-logic unit (ALU) is the heart of the processor, performing arithmetic and logic operations on data. If you've studied digital logic, you've probably learned how to combine simple binary adder circuits to build an ALU. However, the 8008's ALU uses clever logic circuits that can perform multip
Computer history, restoring vintage computers, IC reverse engineering, and whatever The revolutionary Xerox Alto computer came out in 1973 and set the direction for personal computing. If you want to try out the Alto's software, the easiest approach is the ContrAlto simulator. This article describes how to set up the ContrAlto simulator, explains where to find Alto disk images, and shows some of t
Computer history, restoring vintage computers, IC reverse engineering, and whatever Star characters (☆★) have long been part of the Unicode standard, which means they can appear as characters in web pages, text, and email. But half-stars were missing, so they required special images or custom fonts. I recently co-wrote a proposal to add half-star characters to Unicode, and it was just accepted. In
Computer history, restoring vintage computers, IC reverse engineering, and whatever Have you ever wondered what's inside your Macbook's charger? There's a lot more circuitry crammed into the compact power adapter than you'd expect, including a microprocessor. This charger teardown looks at the numerous components in the charger and explains how they work together to power your laptop. Most consume
Computer history, restoring vintage computers, IC reverse engineering, and whatever The 8-bit Z80 microprocessor is famed for use in many early personal computers such the Osborne 1, TRS-80, and Sinclair ZX Spectrum. The Z80 has an innovative design for its internal registers, with two sets of general-purpose registers. The diagram below shows a highly-magnified photo of the Z80 chip, from the Vis
Computer history, restoring vintage computers, IC reverse engineering, and whatever I decided to see how practical it would be to mine Bitcoin with pencil and paper. It turns out that the SHA-256 algorithm used for mining is pretty simple and can in fact be done by hand. Not surprisingly, the process is extremely slow compared to hardware mining and is entirely impractical. But performing the algo
Computer history, restoring vintage computers, IC reverse engineering, and whatever Apple sells their iPad charger for $19, while you can buy an iPad charger on eBay for about $3. From the outside, the chargers look the same. Is there a difference besides the price? In this article, I look inside real and counterfeit chargers and find that the genuine charger has much better construction, power qu
Computer history, restoring vintage computers, IC reverse engineering, and whatever This article explains Bitcoin mining in details, right down to the hex data and network traffic. If you've ever wondered what really happens in Bitcoin mining, you've come to the right place. My previous article, Bitcoins the hard way described how I manually created a Bitcoin transaction and sent it into the syste
Computer history, restoring vintage computers, IC reverse engineering, and whatever All the recent media attention on Bitcoin inspired me to learn how Bitcoin really works, right down to the bytes flowing through the network. Normal people use software[1] that hides what is really going on, but I wanted to get a hands-on understanding of the Bitcoin protocol. My goal was to use the Bitcoin system
Computer history, restoring vintage computers, IC reverse engineering, and whatever How Hacker News ranking really works: scoring, controversy, and penalties The basic formula for Hacker News ranking has been known for years, but questions remained. Does the published code give the real algorithm? Are rankings purely based on votes or do invisible factors come into play? Do stories about the NSA g
Computer history, restoring vintage computers, IC reverse engineering, and whatever The 8-bit Z-80 processor is famed for use in many early personal computers such the Osborne 1, TRS-80, and Sinclair ZX Spectrum, and it is still used in embedded systems and TI graphing calculators. I had always assumed that the ALU (arithmetic-logic unit) in the Z-80 was 8 bits wide, like just about every other 8-
Computer history, restoring vintage computers, IC reverse engineering, and whatever The 8085 microprocessor has two undocumented status flags: V and K. These flags can be reverse-engineered by looking at the silicon of the chip, and their function turns out to be different from previous explanations. In addition, the implementation of these flags shows that they were deliberately implemented, whic
Computer history, restoring vintage computers, IC reverse engineering, and whatever In this article, I show how overflow is computed in the 6502 microprocessor at the transistor and silicon level. I've discussed the mathematics of the 6502 overflow flag earlier and thought it would be interesting to look at the actual chip-level implementation. Even though the overflow flag is a slightly obscure f
Computer history, restoring vintage computers, IC reverse engineering, and whatever I recently came across the site worrydream.com, which implements an amazing navigation experience through JavaScript and HTML5. The page displays dozens of page icons arranged into angled strips that fit the page, and when you click on one, the icons fly around the page while the clicked link slides in at the botto
Computer history, restoring vintage computers, IC reverse engineering, and whatever A dozen USB chargers in the lab: Apple is very good, but not quite the best When you buy a USB charger, how do you know if you're getting a safe, high-quality charger for your money? You can't tell from the outside if a charger provides silky-smooth power or if it is a dangerous charger that emits noisy power that
Computer history, restoring vintage computers, IC reverse engineering, and whatever Pulse-width modulation (PWM) can be implemented on the Arduino in several ways. This article explains simple PWM techniques, as well as how to use the PWM registers directly for more control over the duty cycle and frequency. This article focuses on the Arduino Diecimila and Duemilanove models, which use the ATmega
Computer history, restoring vintage computers, IC reverse engineering, and whatever Disassembling Apple's diminutive inch-cube iPhone charger reveals a technologically advanced flyback switching power supply that goes beyond the typical charger. It simply takes AC input (anything between 100 and 240 volts) and produce 5 watts of smooth 5 volt power, but the circuit to do this is surprisingly compl
Computer history, restoring vintage computers, IC reverse engineering, and whatever Thoughts on the death of Ma Ailun According to reports, a woman in China was tragically electrocuted using her iPhone while it was charging. This seems technically plausible to me if she were using a cheap or counterfeit charger like I describe below. There's 340 volts DC inside the charger, which is enough to kill
Computer history, restoring vintage computers, IC reverse engineering, and whatever The new biography Steve Jobs contains a remarkable claim about the power supply of the Apple II and its designer Rod Holt:[1] Instead of a conventional linear power supply, Holt built one like those used in oscilloscopes. It switched the power on and off not sixty times per second, but thousands of times; this allo
Computer history, restoring vintage computers, IC reverse engineering, and whatever A new multi-branch algorithm to render rational-exponent Mandelbrot fractals: Part I If you came here from Hacker News, thanks for visiting. You might want to check out the Hacker News comment thread too. The Mandelbrot fractal is generated by repeatedly iterating the complex function f(z) = z^2 + c, and testing if
Code now on github The most recent code is at github.com/shirriff/Arduino-IRremote. If you have any issues, please report them there. Do you want to control your Arduino with an IR remote? Do you want to use your Arduino to control your stereo or other devices? This IR remote library lets you both send and receive IR remote codes in multiple protocols. It supports NEC, Sony SIRC, Philips RC5, Phil
Computer history, restoring vintage computers, IC reverse engineering, and whatever The code that implements Arc illustrates many useful programming techniques. Some of the techniques occur multiple times, and can be considered idioms of Arc programming; techniques that can be applied to many problems. This article describes some of the most common idioms, and how they can be used in Arc programmi
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