Tag: How to Build a Computer

How to Build a Computer 31: Sputtering

 

Today we answer an important question: “How do I coat things in metal; even things that don’t want to be coated in metal?” You want to plate gold onto you Sacajawea dollar, that’s easy enough. You can use electricity to get one metal to stick to another. You want to cover Jill Masterson you use gold paint. But let’s say you’ve got a little plastic doohickey you want to look at under an SEM. Plastic famously refuses to conduct electricity. So how do you defeat the charging problems? (The charging problems that we mentioned last time. You were paying attention, weren’t you?) The answer is you sputter coat it. And this week I’ll be explaining what that means.

Also in the SEM lab; you can tell by the example images they’ve stuck into the window.

Start with an Argon plasma. Hmm… maybe let’s start a little earlier than that. A plasma is a gas where the atoms have an electron stripped off. Also, the stripped off electrons. You’ve got to keep your plasma at a pretty high energy, otherwise your atoms recapture their electrons and you end up with a boring ol’ gas. If you’re the Sun then you can make a plasma by heating up these gases to an enormous temperature. On Earth that’s less convenient, so we use electricity.

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How to Build a Computer 30: SEMsational

 

This is a continuation of last time’s discussion on Electron Microscopy. In that one, we covered the question of why you’d want one of these and gave a summary of how you’d work one. Take some electrons, throw it at your sample, and watch what bounces off for information. Sounds so simple when we put it that way, right? This week we’re talking about what happens when you actually buckle down to do it in practice.

Taken from Chem lab, when there weren’t any chem techs around to stop me.

Okay, just looking at the thing isn’t doing me much good. What’s going on there, and why? Start from the top. That bottle on the left? That’s for liquid nitrogen, used in the x-ray detector. (Neat! Why do we want to detect x-rays? That’s a subject for a future column.) The cylinder on top marked “GEMINI” is your column; the electron gun is in the top, and the rest of it contains the magnets for focusing and directing the electron beam. The cube-ish box it’s sitting on is your sample chamber; the front pulls out to reveal the stage where you’d put your puck holding the samples. The dark grey table surface is granite, used to lend stability to the whole apparatus. The cabinet it’s sitting on contains electronics and the vacuum pumps. Now let’s get to how all that works together.

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Quote of the Day: Computers

 

“On two occasions, I have been asked [by members of Parliament], ‘Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?’…I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.”
Charles Babbage, Passages from the Life of a Philosopher (1864), p. 67

Computers. When designed properly, they do precisely what they are told. They do not interpret, they need to be explicitly instructed on what exactly to do. However, when you get them going, they give you incredible capabilities. During WW2, people would have sacrificed armies to obtain the computing power in your cell phone. Even a simple flip phone has more power than all the computers in existence at the time. Charles Babbage could have revolutionized history, had manufacturing been up to the task — William Gibson’s novel The Difference Engine posits just such a future. (It was the beginning of the Steampunk genre)

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How to Build a Computer 29: Electron Microscopy

 

For the next couple of posts, we’ll be sauntering through the science of measurement. To put it simply, computer bits are really, really small. So as you wander through the world of building them how do you know you’ve made the thing right? Well, let’s start simple. You can just look at ’em. I could go on a great big tear about optical microscopy which is still an important subject, and relevant. The problem with it is that I just don’t find the subject very interesting. Still, you get some neat images.

This is my fingerprint, photographed on the background of one of them hard drive platters I ripped out of that drive in the video. FBI please ignore.

To understand why you need the electron microscope it helps to spend some time with an optical microscope. The majority of the time I spent looking at parts I spent looking through an optical microscope, not on the SEM. Largely because Chem Lab owned the SEM, and they get all fidgety when someone else touches their stuff. Briefly though, I think I can demonstrate the usefulness of an electron microscope with two images.

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How to Build a Computer 28: Video Edition!

 

Coming to you taped from the Wastes of Wisconsin Winter we present a special video edition of how to build a computer. In this post I take apart a hard drive and look at the bits piece by piece. Thrills, chills, blood and laughter, folks this film has it all! And at a price so low I’m practically giving it away.

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How to Build a Computer 27: Data Recovery

 

We’ve covered the physical aspects of a hard disk drive, tonight we’ll touch on the way data is organized on the drive, by covering those two most important topics; keeping secrets and ferreting other people’s out.

In this case describing the times this joke has been used since it was last funny.

We’ll start by deleting files: Let’s say that I’ve got a backlog of old and worn-out memes to purge. That’s no problem, you just move them from the exquisitely detailed and organized archive of these things into the trash can, but that doesn’t actually erase anything. Bill Gates, knowing that we mere mortals are flawed and prone to regret, keeps your trashed files around in case your stale jokes may, someday in the future, be called for again. But we’re stronger than that. So we empty the trash folder (or, pro-tip; on a Windows box if you hold down ‘Shift’ as you delete a file the file doesn’t go to the trash at all; it empties automatically.)

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How to Build a Computer 26: Spindles and Platters and So Forth

 

We’ve discussed what it means to actually store information on a hard disk drive, how you magnetize it and how you pull that information off. Neat stuff, but a bit heavy on the abstract physics. Today we’re going to zoom out a bit and look at the mechanical bits of how hard drives work. Here, let me start you off with a picture. Take a look at these two hard drives (conveniently cracked open for viewing purposes), one I borrowed from the boss man, and the other I picked up off the “Free Stuff” shelf when they moved the engineering department. Tell me which you think stores more data:

None of the above. Neither of is ever going to run again. Look at that dust!

Now I’ve actually got no idea on the history of these two drives, what year they were built, their listed capacity. Couple points of difference tell me the one on the left is older, and stores far less information:

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How to Build a Computer 25: The Magnetoresistive Effect

 

Our story starts with Lord Kelvin, one of the great old school physicists. You can read about his career from John Walker’s old Saturday Night Science. Actually, at the point he enters this story I don’t think Kelvin had made lord yet; he was just some bloke named Thompson. This Thompson fellow was playing around with magnets and electricity and that sort of thing. What he discovered is that you can change the resistance of a wire with a magnetic field. And furthermore that that change in resistance depends on the angle between the wire and the magnetic field.

Let’s take that a little more slowly. Change in resistance when you’re in a magnetic field? Okay, I can buy that; there’s all this nonsense about wires and magnets and whatnot that I’ve been blathering about up until this point. Angle? The resistance in your wire will vary a great deal whether it’s parallel or antiparallel to the magnetic field on your disk. (Antiparallel means parallel, but facing the other direction. The northbound lane on a highway is antiparallel to the southbound lane.) If your wire is running current right-to-left and your magnetic field is pointed left-to-right then your wire’s resistance is at it’s highest because of your antiparallel configuration.

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How to Automate a Job Out of Existence

 

This is an elaboration of a comment I made in @indymb ‘s post “Is there any point in writing to a Congressperson?” and I’m indebted to him and @Misthiocracy (who has experience working for a Canadian Member of Parliament, I understand) for the details on how all this works. Briefly, we’ll look at a simple task done every day in the houses of government and at how we’d train a computer to do it better.

Briefly, as you may have expected, the letter to your Senator isn’t so much read as processed for the minimum amount of information and interaction required. I’ll quote the meat of his description of the process and then describe how I’d go about automating it. You’re encouraged to go back and read his post (and it should go without saying on Ricochet but the comments too).

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How to Build a Computer 24: Reading and Writing

 

Last time we discussed electricity, magnetism, and how you can generate a magnetic field with an electric current. You know what? Let’s jump straight to the kielbasa:

You could start with a salad, but why bother?

If you run a current through the wire you generate a magnetic field in the sausage (which ought to be a magnetizable metal, naturally), and a field between the prongs. Okay, we can use that thing to make a magnetic field, and use it to write fixed magnetic spots to a disk. The question we left off with is ‘how do you read it?’ Actually, I skipped a step. There’s still one important distinction to be drawn in how you write. Why does the magnetic field still write things if the platter isn’t in between those prongs?

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How to Build a Computer 23: Magnets

 

Hard Disk Drives record data using a technology long known to baffle juggalos. The read/write head uses magnets to store information on those disks. How? Why? What does that even mean? Let’s jump in.

What makes a magnet a magnet? Moving electricity. When you get down to the atomic level atoms are magnetic because their electrons are spinning. Glomp a bunch of those atoms together (like sticking magnets one to another) and you have a grain. Get enough grains lined up in the same direction and you have a permanent magnet.

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How to Build a Computer 22: Hard Disk Drives

 

We’re going to take a jaunt entirely out of sequence here, moving from circuits and silicon into larger scale components. Today we’re talking about hard disk drives. Why? Because it’s a fun and interesting technology, because I know a thing or two about it from first-hand experience, but mostly because I’ve got a book to return. And so we’ll take a quick dive into the world of hard disk drives to see what, as the bear over the mountain intended, we can see.

An example HDD. Entirely too dusty to be functional.

Note the term; usually, we refer to these things as ‘hard drives’ and don’t bother to distinguish what kind it is. In the olden days, you had a hard drive and you had a floppy drive. A hard disk drive (hereafter HDD) contains a spinning platter that has the information magnetically encoded on it. A floppy drive also had a spinning platter with information on it, but that spinning part was bendable. For all you youngsters out there your “Save” icon is supposed to look like a floppy disk. It dates back to the times when people actually saved files for storage on one of ’em. The structure of the disks was rigid, you didn’t see the floppy part until you took the thing apart.

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Member Post

 

As a kid in the Boy Scouts we’d go camping occasionally at Fort Gibson. This, you see, was the name the eponymous Mr. Gibson gave to his extensive tract of land along the south fork of the Flambeau River. Being a firm proponent of the principle that Men are just Boys with bigger Toys he […]

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How to Build a Computer 20: Digital Watches

 

Because I’m the sort of simian who still thinks that digital watches are pretty neat, I figured I’d work through a practical example. We know how to represent binary numbers, and we know how to express logic with gates. That’s enough knowledge to be dangerous. From there I worked out how to light the lights on a digital watch face. Here, let me show you. But first a quick disclaimer. This isn’t my area of expertise; odds are there are plenty of ways to do this better or more efficiently. I can say at least that this one works.

Okay, let’s talk numbers. Recall from the discussion of binary that you can express any normal number as a series of ones and zeros. So, for example, you could draw One (that is, the presence of bread) in the 4’s place, one in the 2’s place, one in the 1’s place. 4 + 2 + 1 = 7

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How to Build a Computer 19: Logic Gates

 

Welcome back to How to Build a Computer. You recall where we’re at, right? Hah! Trick question. As if I’d stick to a rational sequence. Today we’re going over some of the details in how you go from electrical circuits doing whatever it is that electrical circuits do and turn that into logic. We’re talking Logical Gates

Logic gates! Each one more logical than the last.

Logic gates are transistor circuits that you can use to modify a signal. Let’s take the NOT gate as an example. If the input is on, the output is off. If the input is off, the output turns on. Whatever you put in, you get not-that coming out. Simple enough. Except the part where you’re creating energy out of nothing; what’s up with that? Well, not pictured you’ve got a five-volt source and a grounded drain. When you’re creating energy out of nothing you’re actually stealing it from that source. Those details make laying out your circuits more complicated but can generally be ignored when you’re drawing logic gates. Heck, as long as I’m recycling my drawings have another:

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Member Post

 

Listen, I’m going to be straight with you. This one is mostly for my fun. I mean, they’re all up largely because I like to hear the sound of my own voice. But this one, this one is a bit superfluous. This is the quantum mechanical explanation for how semiconductors work. I’ve already described the […]

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How to Build a Computer 10001: Binary

 

We’ve just come off a long saunter through the manufacturing process. We’ll go back soon enough I promise you, but I figured that we could stand a changeup. We’ll be visiting the wild and wonderful world of binary today. Despite what you may have been told there will be math.

The 10 Types of People in This World

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Member Post

 

Today we’re talking about strippers. By which I mean the machines and the process of stripping photoresist off of your material once the pattern has been applied. Now, the main problem with the strip operation, before you even get to the chemistry involved, is the number of bad jokes that are available. You don’t start […]

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How to Build a Computer 15: Developing

 

No, this isn’t a story that’s still in progress, this is a process step. ‘Developing’ in this context means you’re chemically removing half your photoresist (either the stuff that was exposed in a positive photoresist or the stuff that wasn’t in a negative photoresist.) And no, it’s not about guys making software either. Look, if you’re going to stop us every single time the chance for a bad joke comes up… actually that’s pretty much the game plan. Carry on.

An exposed photoresist molecule. The cheese is carbon, the sausage is oxygen, and I’m thinking it’s high time to conduct some more chemistry, if you know what I mean.

Recall the cheese and sausage photoresist molecule from earlier: That group on the right, that’s a carboxylic acid group. Keyword there being ‘acid’. Add a base to it and you’ll fizz away the resist like Sean Connery’s chest wound in The Last Crusade. Exactly like it. I think they passed off a science-fair baking soda volcano like it was Hollywood magic. But no matter. Developing.

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The Texas Two-Step

 

In a recent installment of @hankrhody ‘s excellent (and delicious) series on building a computer, he wrote about how to do a binary search. In the comments, I made an oblique reference to a better way to do that kind of matching, referring to something I called the Texas Two-Step.

Now don’t get me wrong; in many situations Hank’s solution is an excellent choice, particularly if you want to do a single, real-time lookup. For a single or only a few lookups, Hank’s way is hard to beat. But what if you want to shuffle the whole deck?

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