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Reverse engineering the Intel 386 processor's register cell
The groundbreaking Intel 386 processor (1985) was the first 32-bit processor in the x86 line. It has numerous internal registers: general-purpose registers, index registers, segment selectors, and more...
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Inside the Intel 386 processor die: the clock circuit
Processors are driven by a clock, which controls the timing of each step inside the chip. In this blog post, I'll examine the clock-generation circuitry inside the Intel 386 processor. Earlier...
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Reverse engineering the barrel shifter circuit on the Intel 386 processor die
The Intel 386 processor (1985) was a large step from the 286 processor, moving x86 to a 32-bit architecture. The 386 also dramatically improved the performance of shift and rotate operations by adding...
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Two interesting XOR circuits inside the Intel 386 processor
Intel's 386 processor (1985) was an important advance in the x86 architecture, not only moving to a 32-bit processor but also switching to a CMOS implementation. I've been reverse-engineering parts of...
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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 and took photos. This chip is very unusual: instead of a...
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Interesting double-poly latches inside AMD's vintage LANCE Ethernet chip
I've studied a lot of chips from the 1970s and 1980s, so I usually know what to expect. But an Ethernet chip from 1982 had something new: a strange layer of yellow wiring on the die. After some study,...
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Inside the mechanical Bendix Air Data Computer, part 3: pressure transducers
MathJax.Hub.Config({ "HTML-CSS": { scale: 175} }); .MathJax {font-size: 1em !important} The Bendix Central Air Data Computer (CADC) is an electromechanical analog computer that uses gears and cams for...
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Reverse engineering CMOS, illustrated with a vintage Soviet counter chip
I recently came across an interesting die photo of a Soviet1 chip, probably designed in the 1970s. This article provides an introductory guide to reverse-engineering CMOS circuits, using this chip as...
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Reverse engineering standard cell logic in the Intel 386 processor
The 386 processor (1985) was Intel's most complex processor at the time, with 285,000 transistors. Intel had scheduled 50 person-years to design the processor, but it was falling behind schedule. The...
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Reverse-engineering an analog Bendix air data computer: part 4, the Mach section
MathJax.Hub.Config({ "HTML-CSS": { scale: 175} }); .MathJax {font-size: 1em !important} In the 1950s, many fighter planes used the Bendix Central Air Data Computer (CADC) to compute airspeed, Mach...
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Inside the mechanical Bendix Air Data Computer, part 5: motor/tachometers
The Bendix Central Air Data Computer (CADC) is an electromechanical analog computer that uses gears and cams for its mathematics. It was a key part of military planes such as the F-101 and the F-111...
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The first microcomputer: The transfluxor-powered Arma Micro Computer from 1962
What would you say is the first microcomputer?1 The Apple I from 1976? The Altair 8800 from 1974? Perhaps the lesser-known Micral N (1973) or Q1 (1972)? How about the Arma Micro Computer from way back...
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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 IBM PC (1981) was a critical point in computer history,...
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Inside an unusual 7400-series chip implemented with a gate array
When I look inside a chip from the popular 7400 series, I know what to expect: a fairly simple die, implemented in a straightforward, cost-effective way. However, when I looked inside a military-grade...
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Talking to memory: Inside the Intel 8088 processor's bus interface state machine
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 IBM PC (1981) was a critical point in computer history,...
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Inside a vintage aerospace navigation computer of uncertain purpose
I recently obtained an aerospace computer from the early 1970s, apparently part of a navigation system. Aerospace computers are an interesting but mostly neglected area of computer hardware, so I'm...
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Inside the tiny chip that powers Montreal subway tickets
To use the Montreal subway (the Métro), you tap a paper ticket against the turnstile and it opens. The ticket works through a system called NFC, but what's happening internally? How does the ticket...
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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 original Pentium was followed by the Pentium Pro, the Pentium II,...
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Inside an IBM/Motorola mainframe controller chip from 1981
In this article, I look inside a chip in the IBM 3274 Control Unit.1 But before I discuss the chip, I need to give some background on mainframes. (I didn't completely analyze the chip, so don't expect...
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Reverse engineering the 59-pound printer onboard the Space Shuttle
The Space Shuttle contained a bulky printer so the astronauts could receive procedures, mission plans, weather reports, crew activity plans, and other documents. Needed for the first Shuttle launch in...
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