Observation
Before removing/installing a new hard drive, it’s important that you spend a few minutes examining the interconnections between motherboard, hard drive, and CD-ROM drive. CD-ROM (or optical) drives and hard drives both fall into the category of IDE devices. You can typically install up to four IDE devices on your computer, in any combination you wish. Obviously, you want to have at least one hard drive in the mix so that an operating system can be installed on your computer.
You’ll notice that there are only two IDE cables. Each cable is designed to support two IDE devices. Thus, on each cable you will see three connectors: one connector that is plugged into the motherboard, and two other connectors that are plugged into your IDE devices. If you choose to install only one IDE device on a particular cable, use the end connector, not the middle connector.
There are some configuration options you will need to be familiar with, but first begin by observing where the two IDE cables connect to the motherboard. The IDE interfaces on the motherboard are not created equal. One is referred to as the Primary IDE interface, and the other as the Secondary IDE interface. The motherboard will be labeled in some fashion so that you can distinguish primary from secondary. The labeling scheme varies among manufacturers: you may see the words ‘Primary’ and ‘Secondary’, the abbreviations ‘Pri’ and ‘Sec’, or the numbers ‘1’ and 2’.
What’s important to note is that you can use the primary IDE interface without using the secondary, but not vice versa. If you have one IDE device, a hard drive for example, it must be placed on the primary IDE interface. If you have two IDE devices, such as a hard drive and a CD-ROM drive, you have two options:
If you opt to use both the primary and secondary interfaces, be sure that your boot device – the hard drive – is placed on the primary.
Aside from connecting your IDE devices to the appropriate interfaces, some additional configuration is required. Here’s why. If you have two IDE devices on the same interface (e.g. hard drive and CD-ROM drive or a second hard drive both connected to the cable of the Primary IDE interface), the CPU needs to know which device to address, since they’re both connected to the same cable. The way the two devices are differentiated is by designating one as what is referred to as the ‘Master’ and designating the other as ‘Slave’.
The way this is done is by using a small jumper that is already inserted onto a pin array that’s on the IDE device. To locate this pin array, you should have a look at the rear of the device.
Notice on the back of the hard drive, for example, the two connectors that are attached. The smaller one is the power connector, and incorporates several multicolored wires that terminate in a small connector that’s plugged into the rear of the device. This supplies power to the mechanical and electronic components of the hard drive (or optical drive).
The second connector is the data cable, a wide flat ribbon cable that is used to transmit data both ways between the CPU and the hard drive.
Adjacent to these two connectors is a small recessed pin array. If you look closely you will see that a small jumper block will be inserted across a pair of the pins. Just make the observation for now; you won’t actually set this on the new drive until you’re ready to install it. Further, until the old drive is out, you may not be able to ascertain which set of pins corresponds to ‘master’ and which to ‘slave’. This information is usually imprinted somewhere near the pin array, either on the plastic housing, or more frequently, on the circuit board that is attached to the bottom of the hard drive. There is also a ‘single’ drive designation; when a drive is the only drive on a particular cable, it can be set to either ‘master’ or ‘single’.
Before swapping out hard drives, there’s one more important observation you need to make. The socket on the motherboard into which the IDE ribbon cable is plugged has 40 pins, as does the corresponding socket on the hard drive. These pins are numbered 1 through 40, although due to space limitations, usually only pin 1 or pin 2 is actually labeled.
In order to make sure the communications path between the motherboard and the hard drive is synchronized, you must make sure that pin 1 on the motherboard socket is connected to pin 1 on the IDE device (hard drive or optical drive). While many ribbon cables are keyed so that they can only be inserted into the socket to assure this match takes place, some cables can be accidentally reversed. Thus, it’s critical that you locate pin 1 on both ends, and make sure the ribbon cable is connected such that pin 1 is connected to pin 1.
There’s a visual aid on the ribbon cable itself to assist you with this. Notice that there is one side of the cable with a wire that is colored differently from the other wires – often red, sometimes blue or green. The convention in the field is to be sure that the colored wire on the ribbon cable is used to connect pin 1 of the motherboard to pin 1 of the connected IDE device. You should abide by this convention.
Items Needed
Note that in most cases the drive is mounted to the drive bay with screws, and is removed from the computer from the inside of the case. There are a few case designs that allow for spring-loaded removal of the drive from the front of the case. There’s also a high-speed variation of ATA called Ultra ATA which requires an 80-pin interface cable.