On this page I dissect a Performa 6200 CD. See also the Apple Vintage and Obsolete Products page. Images have been enlarged to show texture.


This is what an internal CD-ROM drive looks like outside of its case. Normally, an "external" cd drive is simply one of these guys inside of a fancy-looking case. I should mention here that CD-ROM stands for Compact Disk - Read Only Memory and it would be considered an I/O device. It is very similar to a punch-card reader, but it's a bit faster. Lets do some math... a standard punch card will hold 80 Bytes of information, while a cd will hold 700 MBytes (aka 700,000,000 Bytes). That means that the contents of 8,750,000 punch cards will fit on a single cd. Also, a 24x cd will read information at ~3.7 MBytes per second (aka ~3,700,000 Bytes per second). That means we are talking about 46,250 punch cards per second. Each punch card would have to be traveling well over the speed of sound. Isn't technology great? :-)


And this is what the internal cd drive looks like when you pull its cover off.


You can see how when the tray retracts into the drive the spindle lines up with the hole in the middle of any cd. Just above the spindle you can see the laser that moves back and fourth on a track and reads information off of the disk as the disk spins. The laser is able to do this because it is focused onto a small point in between the layers of plastic in the CD where there is a thin layer of aluminum. The surface of this aluminum is either reflective, or it isn't. By reading the reflections off of the surface of the disk, the drive can read the binary information on the disk. Binary information (1s and 0s) translates into music, or whatever else can be stored on a CD. A writeable cd might not have aluminum in it, but it will have something that is similarly reflective. A cd burner works by simply darkening areas in the CD so that the reflective area isn't reflective.


This is a floppy drive that was pulled out of the computer case. Be glad if you don't immediately recognize it.


This is an internal hard drive. The one that we are looking at here could hold 1 GB (1,000,000,000 bytes) of information before I broke it by taking the top off. Hard drives tend to be able to hold more information now-a-days. For example, I have two in my home computer that can each hold 250 GB of information. Fun stuff.


This is what the hard drive looks like when you pull it apart. Don't try this at home kids. The read/write head you can see there does its job by floating a few millionths of an inch above the platter as the platter is spinning. If the head comes in contact with the disk (instead of floating just above it) it is called a head crash. Head crashes are rather nasty things that tend to completely destroy a hard drive. This is why you back up your computer, folks. Here is a link to a rather nasty head crash. Anyway, the platter of the hard drive is polished very smooth so the heads can safely fly around on them. If something even as large as a speck of dust were to get on the platter, the result would kind of look like a mountain range to the head. The result isn't pretty.


Here is the board the handles the logic. It is normally placed on the bottom of a hard drive. It translates between the disk locations that the Operating System (aka Windows, Linux, or Mac OS X) specifies to read, and the actual electrical signals that move the actuator arm, etc.


This is the first thing that we have looked at which isn't an I/O device. This is the power supply. If you don't purchase a good one, it will go nuts and start frying things in your computer. Want to know what is missing in a $400 PC? More likely than not, a good power supply.


Here is the motherboard from the computer. On a normal computer, you would see a number of cables coming off of it to connect it to the I/O devices that we mentioned and the power supply. This isn't a normal computer, because that odd white slotted thing along the upper left makes all of those connections instead. Something else missing is the big processor and heat sink. You see, back in the old days computers had efficient processors that didn't require enough wattage to power a toaster. On modern PCs, all that energy has to go somewhere once it is used, it just doesn't disappear on its own. So, you end up with 130 watts of heat energy in something the size of a postage stamp. If you do the math, that is more heat energy per square inch than your average clothes iron. Or toaster oven. It gets really hot if you let it. The trick is, the processor would much rather operate at a cold temperature, such as freezing, and if you don't cool it down some how, it will toast itself (literally) and release the magic blue smoke. (The processor operates when the smoke is in it, but stops working when the smoke leaves. It's like magic, you see?) So, on most modern PCs you will see a massive contraption covering the processor that is designed to cool it down to something approaching room temperature. Occasionally, people will go nuts and make rather "special" contraptions to cool their processors further in order to pull a bit extra speed out of the computer. Getting back to the original point, the computer pictured here didn't need one of those heat sinks, so it doesn't have one.


This is the modem card, probably a 14.4 kbit/sec one. Be glad if you have never heard of modems running at this speed, 56k is plenty slow. A "modem" is simply a device that translates binary into a sound wave that can be transmitted over the phone line.


This is a ROM chip. It contains all of the instructions that are used when you first boot the computer up. It does things like checking to make sure that the memory isn't giving errors and/or you have done something stupid. It also loads up your Operating System. It could be called Firmware or BIOS.


This is the ethernet card. The plug for this looks like a phone plug, but is fatter (more wires). We'll talk more about networks later. This one is a 10 Base-T card, and runs at about 300 KBytes per second.


It's RAM (Random Access Memory). These in particular are SIMMs (Single In-line Memory Module). The RAM stores information, just like the hard drive and CD-ROM drive. It has significant advantages and disadvantages over them, though. Its single main advantage is that it is about a million times faster than either the cd or hard drive. To put that in perspective, it is equivalent to either taking a second to get some information out of RAM, or taking a week to get it off of the hard drive. It does have significant disadvantages, though. Not only is space in RAM much more expensive than space on the hard drive (~500 times more expensive), but everything in RAM is erased when you turn off the computer.


This is a nakkid motherboard. You can see where all of the cards that I mentioned above get plugged in. Generally, components in a computer are designed so in order to plug something in wrong, you need to first bend or break it into position. Thus, things tend to fit together like some sort of clever jigsaw puzzle.