Gregory's Server
The Pentium processor had a minor error in the division algorithm. This error cost Intel $475 million to replace the faulty chips. I've tracked down the FDIV error to this circuit on the die:
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Tiny thumbs-up in the Pentium P5. I found this hidden chip art after removing two layers of metal from the chip. (I don't know who JNL is.)
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 @kenshirriff I hate the Internet so much for making me think that was something horrible at first glance   Here's a die photo of the Pentium chip, the original P5 version introduced in 1993. For this photo, I removed the top metal layer (of the three metal layers), making it easier to see the structures underneath. 1/2
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  @kenshirriff I made a histogram of wealth distribution in the United States, using the Forbes 400 list that just came out. Almost the entire US population is in the red line at the left, one pixel wide. To fit Elon Musk on the graph, each pixel is $500 million wide. In other words, from the perspective of the very rich, $0 and $500 million look the same.
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 @kenshirriff I cannot say how absurd this is. There are a bit more than 800 people who are actually represented in this diagram: The rest is “too poor” to be represented — even if they own (almost) a billion Dollars. If you own less than a billion, we cannot care for you... — I am sure this diagram shows the world view of people like Musk or Bezos.  @flexion That's close to me and I've been there a couple times! Unfortunately they started moving everything out and into a new facility in Wyoming a few years ago, and it's pretty much all empty now. The F-4 fighter plane used an attitude indicator to show the plane's orientation. The ball in this indicator rotates in three axes. How does that work? We took the indicator apart to find out.
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  f-4 was an interesting plane. when i was in the air force, pilots used to joke that the f-4 was living proof of the rule of aerodynamics that given sufficient thrust, even a brick could fly. downside was that when the f-4 lost thrust, it reverted to brick. but they had a long and pretty solid life span in service. Ferroelectric RAM (FRAM) is an unusual type of memory. It is fast and can store data for decades without power. I opened up a FRAM chip to reveal the tiny cubes of PZT, the ferroelectric material that holds the bits.
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 @kenshirriff This brings back memories of an IBM 360 derivative machine from the 1970s that had memory modules made of tiny magnetic core donuts with tiny wires orthogonal to each other. Maybe they were 8K each but the improved ones were 16K I think.  But with those capacities, we're back to having full-length RAM adapter cards in our systems, eh? I miss those days! An interesting chip: the MN3009 analog delay. It uses the bucket-brigade principle to delay an analog signal by passing the signal 256 stages. This provides a delay of up to 12.8 ms for reverb, chorus, or other effects. Unfortunately I cracked the die while decapping. Here's the schematic, from the datasheet. Each stage holds the sampled voltage in a capacitor. The two clock phases push the capacitors up and down like a charge pump, dumping the charge into the next capacitor. Thus, the input signal appears at the output 256 clock cycles later.  @kenshirriff they have a distinctive sound, but you can't stomp on them like you can with a spring reverb Probably the strangest chip that you'll see today: the Intel 2920, a digital signal processor (DSP) from 1979. It was the "first microprocessor capable of translating analog signals into digital data in real time." Chips are usually 16-bit or 32-bit, but this was a 25-bit processor. It didn't have any jump instructions, instead running code in a loop from the 192-word EPROM. Each instruction combined an ALU operation, a shift, and an analog I/O operation. 1/7
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 Am I understanding it correctly that it takes analog signals as input, digitizes them, processes them, and then outputs them as analog again? Strange indeed. I've always thought of DSPs as specialized chips that process an already digital signal that may come from an ADC but also from memory for example.  @kenshirriff reminds me of a MAXQ DSP I read about described as "opcode-less" Every part of the chip would do something every clock cycle, so the "instructions" were nothing but a set of operands for all the units Seems like quite a rare design now -- probably because scheduling, pipelining, and speculative execution have beaten it in total throughput Amazing how silicon design has changed @kenshirriff I remember these! When I was getting my EE degree at Arizona State University back in the mid-80s we had a few development systems for these chips in the lab and I remember reading up on them at the time. They were already obsolete and unused AFAIK but it definitely piqued my curiosity. Sad that they didn't fix the bugs and expand on the concept as it definitely would have been useful. Microchip's dsPIC products came along years later and were very successful in the same space. I recently saw an amazing Navajo rug at the National Gallery of Art. It looks abstract at first, but it is a detailed representation of the Intel Pentium processor. Called "Replica of a Chip", it was created in 1994 by Marilou Schultz, a Navajo/Diné weaver and math teacher. Intel commissioned the weaving as a gift to the American Indian Science & Engineering Society. 1/6
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@kenshirriff Looks a little like launching a Steam game under Wayland and Plasma, which I tried during the weekend @kenshirriff A display made from electromechanical rotating wheels. I applied power to the display, causing digits to rotate. The display is constructed as a matrix. One line selects the digits and one line selects the value of that digit. On the back, each digit has a diode matrix card. In 1989, Intel introduced the 486 processor, improving the performance of the 32-bit 386. Unlike the 386, the 486 has an on-chip 8 KB cache and a floating-point unit. The 486 has over a million transistors.
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The chip I photographed is the i486 SX, which is the version of the 486 without a floating point unit. But you can see from the photo that it has a floating point unit on the die. It's unclear if Intel deliberately disabled the floating point unit to segment the market between the low-end SX and the high-end DX, or if chips with an FPU fault were sold as the SX.  @kenshirriff damn this made me find out that CPU cores are a lot smaller than I thought and occupy less than half of the entire thing, both in modern CPUs and I assume in this one if the decode logic part is what would be described as a CPU core (I don't know that much about computer science) @kenshirriff Are more details coming? The part labeled FPU is surprisingly small compared to the parts labeled data path (control). How much was microcoded? The Minuteman III missile (1970) is America's land-based nuclear deterrent, with 400 missiles ready to launch. The missile used a complex guidance system with over 17,000 electronic and mechanical parts that cost $4.5 million in current dollars. Let's take a look at the guidance system and computer. 1/N 
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@kenshirriff I know this sounds like a dumb question but how did they test that their ICBMs could hit their targets. You can't just fire a dummy ICBM at Russia for obvious reasons. @kenshirriff  @kenshirriff As always, your post is highly interesting. In particular those about embedded systems like this one broaden my understanding of what a computer is, was, and could be. Thanks a lot! The original Pentium chip was introduced in 1993. It was the first "superscalar" x86 chip, able to run two instructions per clock cycle. I took this die photo of the chip yesterday. The chip has three metal layers; the thick lines you see are the top metal layer, mostly power and ground. The silicon itself is almost entirely obscured. Around the edges of the chip, tiny bond wires connect to the bond pads, providing the connections to the chip's external pins. 1/N The original Pentium was power-hungry, so Intel soon released an updated version that could turn off the clock to parts that weren't being used, saving power. The original (P5 architecture, part number 80501) on the left has a noticeably larger die and package than the update (P54C, 80502). The original was built with Intel'ss 800 nm BiCMOS process, while the update was 600 nm.   @kenshirriff I have a lot of affection for the Pentium. The first 64-bit (-data-bus) x86 CPU. 😌 The Space Shuttle had a 59-pound printer on board, known as the Interim Teleprinter. Putting this heavy printer in orbit cost $1.5 million per flight, but it was a key piece of flight hardware,
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  @kenshirriff It cost $1.4 million just to load the ink cartridge and paper and $100,000 to launch it. For those into punch card humor, here's a routine by comedian Bob Newhart, who just passed away: "A call from Herman Hollerith". IBM commissioned this skit in 1970.
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 @kenshirriff @kenshirriff I have some of his stand-up on CD. Lincoln's press agent opens with "Hey, Abe baby! How ya doin?" He used to do a two-hand act, but the other guy wasn't ready to go pro, so Newhart rewrote their routines into one-sided telephone calls. I highly recommend stand-up by Andy Griffith ("Romeo and Juliet"), and the classic Nichols and May (they invented improv comedy). Nichols directed "The Graduate", Elaine May did "Birdcage". Ferocious talents, and mostly forgotten. @kenshirriff thanks Ken, that reminded me of the 1970s and when I used to feed them in, and stand there worrying was this the future of computing! This pretty chip from 1981 helped connect an IBM mainframe to data-entry terminals. 1/14 Mainframes were extremely slow compared to modern computers but they could support rooms full of users. The trick was that mainframes offloaded the text editing to the terminals, while a special "I/O channel processor" pumped data directly into memory without using the CPU. 2/14  @kenshirriff One question that may sound really stupid but "I really cannot understand", you reverse engineer those IBM chips ... But .. does it mean IBM has lost all the lore about them or they don't want to make it publicly available ? Why ? And if that's the case "why they don't come after you for exposing it ?". I mean it's all super cool, super clever, "tremendous exercise" but does it mean "original documentation is lost forever" ?? 🤔  @kenshirriff Oh yes those early chips were so easy to copy. I once watched someone do that job. Intel's Pentium processor (1993) was a big jump in processor performance, starting a brand that lasted until 2023. But what's inside the Pentium chip? How did Intel organize its 3.3 million transistors? Let's take a look inside and see the chip's "standard cells". 1/21 The fingernail-sized Pentium chip under a microscope. Some parts, like the cache and datapath were highly optimized by hand. Less critical areas, outlined in red, were designed by software using standard cells. The rows of cells are visible as gray columns. 2/21 @kenshirriff why am I looking at this and thinking it'd make a wonderfully geeky rug or blanket pattern? To use the Montreal subway, you tap a paper ticket against the turnstile and it opens. But how does it work? And how can the ticket be so cheap that it's disposable? I opened up the tiny NFC chip inside to find out more... 1/15
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 @kenshirriff @kenshirriff Seems wonderful, well, excepted for the "throw it in a paper bin where it won't be correctly recycled" I received a mysterious aerospace computer from the early 1970s, probably for navigation. It is crammed full of flat-pack integrated circuits surrounding a core memory module. Let's take a look inside... 1/17
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 @kenshirriff I need to photoshop it so the display has the characters “P O E”. “Mandrake… do you know why I only drink alcohol or rainwater?” |
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At first glance, I thought this was the map screen from the original Pokémon.
@kenshirriff Intel Inside, can't divide!
@kenshirriff oh that looks like my cuircuit making module in factorio :grin: