Reverse engineering standard cell logic in the Intel 386 processor
http://www.righto.com/2024/01/intel-386-standard-cells.html [www.righto.com]
2024-03-13 07:33
tags:
article
compsci
cpu
hardware
photos
tech
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 design team decided to automate chunks of the layout, developing “automatic place and route” software. This was a risky decision since if the software couldn’t create a dense enough layout, the chip couldn’t be manufactured. But in the end, the 386 finished ahead of schedule, an almost unheard-of accomplishment.
In this article, I take a close look at the “standard cells” used in the 386, the logic blocks that were arranged and wired by software. Reverse-engineering these circuits shows how standard cells implement logic gates, latches, and other components with CMOS transistors. Modern integrated circuits still use standard cells, much smaller now, of course, but built from the same principles.
The complex history of the Intel i960 RISC processor
http://www.righto.com/2023/07/the-complex-history-of-intel-i960-risc.html [www.righto.com]
2023-07-02 01:13
tags:
cpu
hardware
retro
The Intel i960 was a remarkable 32-bit processor of the 1990s with a confusing set of versions. Although it is now mostly forgotten (outside the many people who used it as an embedded processor), it has a complex history. It had a shot at being Intel’s flagship processor until x86 overshadowed it. Later, it was the world’s best-selling RISC processor. One variant was a 33-bit processor with a decidedly non-RISC object-oriented instruction set; it became a military standard and was used in the F-22 fighter plane. Another version powered Intel’s short-lived Unix servers. In this blog post, I’ll take a look at the history of the i960, explain its different variants, and examine silicon dies. This chip has a lot of mythology and confusion (especially on Wikipedia), so I’ll try to clear things up.
source: HN
Inside the amazingly mechanical Bendix Central Air Data Computer
http://www.righto.com/2023/02/bendix-central-air-data-computer-cadc.html [www.righto.com]
2023-03-25 00:33
tags:
flying
hardware
photos
physics
retro
Determining the airspeed and altitude of a fighter plane is harder than you’d expect. At slower speeds, pressure measurements can give the altitude, air speed, and other “air data”. But as planes approach the speed of sound, complicated equations are needed to accurately compute these values. The Bendix Central Air Data Computer (CADC) solved this problem for military planes such as the F-101 and the F-111 fighters, and the B-58 bomber. This electromechanical marvel was crammed full of 1955 technology: gears, cams, synchros, and magnetic amplifiers. In this blog post I look inside the CADC, describe the calculations it performed, and explain how it performed these calculations mechanically.
The 8086 processor's microcode pipeline from die analysis
http://www.righto.com/2023/01/the-8086-processors-microcode-pipeline.html [www.righto.com]
2023-01-27 18:28
tags:
cpu
hardware
investigation
perf
series
The digital ranging system that measured the distance to the Apollo spacecraft
http://www.righto.com/2022/04/the-digital-ranging-system-that.html [www.righto.com]
2022-04-24 18:44
tags:
hardware
random
retro
space
The basic idea was to send a radio signal to the spacecraft and determine how long it takes to return. Since the signal traveled at the speed of light, the time delay gives the distance. The main problem is that due to the extreme distance to the spacecraft, a radar-like return pulse would be too weak. The ranging system solved this in two ways. First, a complex transponder on the spacecraft sent back an amplified signal. Second, instead of sending a pulse, the system transmitted a long pseudorandom bit sequence. By correlating this sequence over multiple seconds, a weak signal could be extracted from the noise.
In this blog post I explain this surprisingly-complex ranging system. Generating and correlating pseudorandom sequences was difficult with the transistor circuitry of the 1960s. The ranging codes had to be integrated with Apollo’s “Unified S-Band” communication system, which used high-frequency microwave signals. Onboard the spacecraft, a special frequency-multiplying transponder supported Doppler speed measurements. Finally, communicating with the spacecraft required a complex network of ground stations spanning the globe.
And: https://righto.com/apollo/ranging-xor.html
http://www.righto.com/2022/05/talking-with-moon-inside-apollos.html
Inside the 8086 processor, tiny charge pumps create a negative voltage
http://www.righto.com/2020/07/inside-8086-processor-tiny-charge-pumps.html [www.righto.com]
2020-07-26 21:25
tags:
cpu
hardware
photos
retro
You might wonder how a charge pump can turn a positive voltage into a negative voltage. The trick is a “flying” capacitor, as shown below. On the left, the capacitor is charged to 5 volts. Now, disconnect the capacitor and connect the positive side to ground. The capacitor still has its 5-volt charge, so now the low side must be at -5 volts. By rapidly switching the capacitor between the two states, the charge pump produces a negative voltage.
Die shrink: How Intel scaled down the 8086 processor
http://www.righto.com/2020/06/die-shrink-how-intel-scaled-down-8086.html [www.righto.com]
2020-07-01 02:23
tags:
cpu
hardware
photos
retro
The revolutionary Intel 8086 microprocessor was introduced 42 years ago this month so I’ve been studying its die. I came across two 8086 dies with different sizes, which reveal details of how a die shrink works. The concept of a die shrink is that as technology improved, a manufacturer could shrink the silicon die, reducing costs and improving performance. But there’s more to it than simply scaling down the whole die. Although the internal circuitry can be directly scaled down, external-facing features can’t shrink as easily. For instance, the bonding pads need a minimum size so wires can be attached, and the power-distribution traces must be large enough for the current. The result is that Intel scaled the interior of the 8086 without change, but the circuitry and pads around the edge of the chip were redesigned.
Reverse-engineering and comparing two Game Boy audio amplifier chips
http://www.righto.com/2020/06/reverse-engineering-and-comparing-two.html [www.righto.com]
2020-06-22 02:05
tags:
audio
gaming
hardware
The Nintendo Game Boy contains an audio amplifier chip for sound through a speaker or headphones. In this post, I reverse-engineer this chip and compare it with the later Game Boy Color chip (reverse-engineered earlier). Unexpectedly the Game Boy Color uses an entirely different amplifier design from the original Game Boy, which may explain why the two systems sound different.
Extracting ROM constants from the 8087 math coprocessor's die
http://www.righto.com/2020/05/extracting-rom-constants-from-8087-math.html [www.righto.com]
2020-05-17 23:20
tags:
hardware
math
photos
retro
I opened up an 8087 chip and took photos with a microscope. The photo below shows the chip’s tiny silicon die. Around the edges of the chip, tiny bond wires connect the chip to the 40 external pins. The labels show the main functional blocks, based on my reverse engineering. By examining the chip closely, various constants can be read out of the chip’s ROM, numbers such as pi that the chip uses in its calculations.
Tiny transformer inside: Decapping an isolated power transfer chip
http://www.righto.com/2020/05/tiny-transformer-inside-decapping.html [www.righto.com]
2020-05-09 19:12
tags:
energy
hardware
investigation
photos
solder
I saw an ad for a tiny chip that provides 5 volts of isolated power: You feed 5 volts in one side, and get 5 volts out the other side. What makes this remarkable is that the two sides can have up to 5000 volts between them. This chip contains a DC-DC converter and a tiny isolation transformer so there’s no direct electrical connection from one side to the other. I was amazed that they could fit all this into a package smaller than your fingernail, so I decided to take a look inside.
How "special register groups" invaded computer dictionaries for decades
http://www.righto.com/2019/10/how-special-register-groups-invaded.html [www.righto.com]
2019-10-23 05:29
tags:
cpu
hardware
investigation
langauge
retro
Half a century ago, the puzzling phrase “special register groups” started showing up in definitions of “CPU”, and it is still there. In this blog post, I uncover how special register groups went from an obscure feature in the Honeywell 800 mainframe to appearing in the Washington Post.
A visit to the Large Scale Systems Museum
http://www.righto.com/2019/10/a-visit-to-large-scale-systems-museum.html [www.righto.com]
2019-10-10 19:00
tags:
hardware
photos
retro
travel
I didn’t expect to find two floors filled with vintage computers in a sleepy town outside Pittsburgh. But that’s the location of the Large Scale System Museum, housed in an abandoned department store. The ground floor of this private collection concentrates on mainframes and minicomputers from the 1970s to 1990s featuring IBM, Cray, and DEC systems, along with less common computers. Amazingly, most of these vintage systems are working. Upstairs, the museum is filled with vintage home computers from the pre-PC era.
Reverse-engineering precision op amps from a 1969 analog computer
http://www.righto.com/2019/09/reverse-engineering-precision-op-amps.html [www.righto.com]
2019-09-24 03:45
tags:
hardware
photos
retro
tech
We are restoring a vintage1 computer that CuriousMarc recently obtained. Analog computers were formerly popular for fast scientific computation, but pretty much died out in the 1970s. They are interesting, though, as a completely different computing paradigm from digital computers. In this blog post, I’m going to focus on the op amps used in Marc’s analog computer, a Simulators Inc. model 240.
An analog computer performs computations using physical, continuously changeable values such as voltages. This is in contrast to a digital computer that uses discrete binary values. Analog computers have a long history including gear mechanisms, slide rules, wheel-and-disk integrators, tide computers, and mechanical gun targeting systems. The “classic” analog computers of the 1950s and 1960s, however, used op amps and integrators to solve differential equations. They were typically programmed by plugging cables into a patch panel, yielding a spaghetti-like tangle of wires.
Plus some good references to more about analog computers.
Ken Thompson did some of his early programming on an early analog computer, although I’m unsure of which model.
Iconic consoles of the IBM System/360 mainframes, 55 years old
http://www.righto.com/2019/04/iconic-consoles-of-ibm-system360.html [www.righto.com]
2019-04-15 18:26
tags:
archive
best
hardware
photos
retro
ux
The IBM System/360 was a groundbreaking family of mainframe computers announced on April 7, 1964. Designing the System/360 was an extremely risky “bet-the-company” project for IBM, costing over $5 billion. Although the project ran into severe problems, especially with the software, it was a huge success, one of the top three business accomplishments of all time. System/360 set the direction of the computer industry for decades and popularized features such as the byte, 32-bit words, microcode, and standardized interfaces. The S/360 architecture was so successful that it is still supported by IBM’s latest z/Architecture mainframes, 55 years later.
The lower part of the Model 30 console was used for operator intervention. Note the binary-to-hexadecimal conversion chart below the hexadecimal dials.
While we’re looking: http://www.righto.com/2019/04/a-look-at-ibm-s360-core-memory-in-1960s.html
Inside the Apollo Guidance Computer's core memory
http://www.righto.com/2019/01/inside-apollo-guidance-computers-core.html [www.righto.com]
2019-01-30 21:34
tags:
hardware
malloc
photos
retro
series
space
The Apollo Guidance Computer (AGC) provided guidance, navigation and control onboard the Apollo flights to the Moon. This historic computer was one of the first to use integrated circuits, containing just two types of ICs: a 3-input NOR gate for the logic circuitry and a sense amplifier IC for the memory. It also used numerous analog circuits built from discrete components using unusual cordwood construction.
Also core rope: http://www.righto.com/2019/07/software-woven-into-wire-core-rope-and.html
Erasable core memory and core rope both used magnetic cores, small magnetizable rings. But while erasable core memory used one core for each bit, core rope stored an incredible 192 bits per core, achieving much higher density.2 The trick was to put many wires through each core (as shown above), hardwiring the data: a 1 bit was stored by threading a wire through a core, while the wire bypassed the core for a 0 bit. Thus, once a core rope was carefully manufactured, using a half-mile of wire, data was permanently stored in the core rope.
Also, Bitcoin: http://www.righto.com/2019/07/bitcoin-mining-on-apollo-guidance.html
Also, NOR gates: http://www.righto.com/2019/09/a-computer-built-from-nor-gates-inside.html
This historic computer was one of the first to use integrated circuits and its CPU was built entirely from NOR gates. In this blog post, I describe the architecture and circuitry of the CPU.
Also: https://www.wsj.com/articles/an-apollo-spacecraft-computer-is-brought-back-to-life-11563152761
Two bits per transistor: high-density ROM in Intel's 8087 floating point chip
http://www.righto.com/2018/09/two-bits-per-transistor-high-density.html [www.righto.com]
2018-10-01 17:16
tags:
cpu
hardware
retro
The 8087 chip provided fast floating point arithmetic for the original IBM PC and became part of the x86 architecture used today. One unusual feature of the 8087 is it contained a multi-level ROM (Read-Only Memory) that stored two bits per transistor, twice as dense as a normal ROM. Instead of storing binary data, each cell in the 8087’s ROM stored one of four different values, which were then decoded into two bits. Because the 8087 required a large ROM for microcode1 and the chip was pushing the limits of how many transistors could fit on a chip, Intel used this special technique to make the ROM fit. In this article, I explain how Intel implemented this multi-level ROM.
Glowing mercury thyratrons: inside a 1940s Teletype switching power supply
http://www.righto.com/2018/09/glowing-mercury-thyratrons-inside-1940s.html [www.righto.com]
2018-09-07 23:32
tags:
hardware
photos
retro
tty
We recently started restoring a Teletype Model 19, a Navy communication system introduced in the 1940s. This Teletype was powered by a bulky DC power supply called the “REC-30 rectifier”. The power supply uses special mercury-vapor thyratron tubes, which give off an eerie blue glow in operation, as you can see below.
A 1970s disk drive that wouldn't seek: getting our Xerox Alto running again
http://www.righto.com/2018/03/a-1970s-disk-drive-that-wouldnt-seek.html [www.righto.com]
2018-04-12 16:32
tags:
bugfix
hardware
retro
storage
Our vintage Xerox Alto has been running reliably for months, but a couple weeks ago the disk drive malfunctioned and the heads stopped moving. With a drive that wouldn’t seek, our Alto wouldn’t work. After extensive debugging and studying the drive’s complex head movement control system, we discovered that the problem had a trivial fix. This blog post discusses our adventures debugging the Alto’s Diablo hard drive and how we got it to work again.
Implementing FizzBuzz on an FPGA
http://www.righto.com/2018/03/implementing-fizzbuzz-on-fpga.html [www.righto.com]
2018-03-29 23:15
tags:
hardware
programming
solder
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 gates and flip flops. It’s like having a custom chip that can be anything from a logic analyzer to a microprocessor to a video generator.
Xerox Alto's 3 Mb/s Ethernet: Building a gateway with a BeagleBone
http://www.righto.com/2018/01/xerox-altos-3-mbs-ethernet-building.html [www.righto.com]
2018-01-11 14:55
tags:
hardware
networking
retro
solder
The Alto’s 3 Mb/s Ethernet isn’t compatible with modern Ethernet, making it difficult to transfer data between an Alto and the outside world. To solve this, I built a gateway using the BeagleBone single-board computer to communicate with the Alto’s Ethernet. In this article I discuss how the Alto’s Ethernet works and how I implemented the gateway.
source: L