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The first kind of knowledge is a sort of "how it all fits together" knowledge, an understanding of things like how extended memory is different from conventional memory or what a superscalar CPU is. It's knowledge of the components and interfaces-the connections between those components-that enables you to diagnose a problem or select the correct upgrade part. You'll learn about this kind of "microcomputer anatomy and physiology" throughout most of the rest of the book-in fact, the extended/expanded and superscalar stuff is in the next chapter.
The second sort of knowledge that you'll need is a different kind, a familiarity with tools and with some simple rules of disassembly. Perhaps it's my personal bias, but I prefer to teach these skills before getting into the concepts of Chapter 3. It may be that I do that because I'm kind of clumsy personally: I'm the kind of guy who forgets to put the plug in the bottom of the oil pan before I start refilling the engine with oil, so this has been hard- won knowledge. That won't be true for all of you-if you're already someone who's comfortable with tools, then you probably don't have to be reminded that screwdrivers go "lefty loosey, righty tighty" - but us klutzes do, at least sometimes, and that's what this chapter is about. There are right ways to take a machine apart and wrong ways; this chapter shows you one of the right ways.
That's why Phillips screws were invented. Phillips screws not only have two slots at right angles to one another, they also have an indentation at the intersection of the two slots; a corresponding peak in the Phillips screwdriver shaft fits nicely into that indentation, helping the screwdriver to stay centered.
Or, at least, that's the idea.
There are two problems with Phillips screws, at least in the PC business. First, the screws that PC makers use seem to be all made of some kind of soft, presumably cheap, aluminum. The slots aren't very deep, and the combination of the two means that it's often easy to strip the heads of the screws. So be careful when removing Phillips screws.
The second problem is related to the first. It seems that half of the computers that I work on have previously been worked by Ignatz the Strong Man, apparently on loan from the circus. People tighten PC case screws as if their data will leak out of the seams otherwise. It's a dumb practice for two reasons-first, it's unnecessary, and second, you'll strip the heads on the screws. Tighten to a snug fit, don't cinch it down like it'll be subjected to a vibration test. And another thought along those lines: there are several sizes of Phillips screwdrivers. I'm aware of size 000, 00, 0, 1, 2, and 3, but I'm sure there are more. Most PC screws are size 1; however, the little ones on the interface cable connectors are size 0. You may come across a case screw (one of the screws that secures the case to the chassis) that's a No. 2. The important point is to use the correct size. Don't try to remove a No. 2 with a No. 1 Phillips; again, you'll strip the head.
Personally, I like electric screwdrivers. The Black and Decker that I got for Christmas in 1989 was just about the most useful present I've ever gotten. (And remember, it's made in the US .... )
Compaq computers have used a third type of screw, called a "Torx screw," for years now. The Torx uses a star-shaped hole in the head of the screw. Torx screwdrivers come in at least 15 sizes, which is a major pain for support people. You'll probably only use sizes T- 10 and T-15, but if you want to disassemble hard disks, then you'll find that some hard disks use smaller Torx sizes.
Why do manufacturers use Torx screwdrivers? Well, it's certainly not because of convenience; whatever they are, they are not that. I think it's because until about 10 years ago, most people didn't have Torx screwdrivers handy, which kept the user's fingers out of the gearbox, so to speak. So a computer company that used Torx fasteners could keep the casual user out. If so, then it was a dumb idea; PC's aren't any good to you if you can't get in them. And anyone who's ever had to change the headlights on a GM car already has a set of Torxes.
While I'm on this topic, let me tell you a quick story. Years ago, I bought a number of PCs from a PC configuration/sales company. We'd specified on the bid that we wanted 100 percent IBM components, as this was 1983 and the clone stuff was a bit iffy on compatibility. The company delivered the PC with seals on the back of the box. When I had trouble installing software on the computer, I broke the seals, took the cover off, and lo! the video board, floppy controller, and hard disk controller weren't IBM products. I called the vendor and explained that he had not fulfilled the contract when he sent us shoddy parts. His answer: that I'd violated the warranty on the computer by removing the seals. (I suppose he would have used Torx fasteners if he'd thought of it.) My answer: after I thanked him for the first really good laugh I'd had in a while, I told him to either take the PCs or outfit them correctly. He did. Now, the moral of the story is not that you should buy IBM parts; that's not necessarily good advice in this day and age. The moral is that you should specify what you want in a PC and make sure that you get it. And if a vendor tries to keep you out of a machine that he sold you, then be suspicious....