BIOS OVERVIEW

A typical IDE/ATA interface supports two devices per motherboard controller. Most systems today have two separate motherboard controllers, allowing for a total of four devices to be attached. An EIDE interface can support up to four devices per controller, for a total of eight devices. EIDE is the same as ATA-2. ATA-2 is an improvement on IDE/ATA that also allows for up to four devices per controller, which equates to eight total devices.

For the purposes of the A+ Core Hardware exam, we will focus on the traditional IDE/ATA standard interface that allows for two devices to be attached to each of the two motherboard controllers. This allows us to have a total of four devices—for example, two hard drives, a CD-ROM, and a tape drive unit.

IDE hard drives, CD-ROMs, floppy drives, and oth

er storage devices have jumper settings that determine the role they will play on an IDE interface. A jumper is a plastic and metal clip that is placed on two or more pins. These pins protrude from a device or a motherboard to close a circuit. With these jumpers, you can set the hard drive to be a master or slave drive, or choose cable-select settings.

Note

If you want to specify a certain connector on an IDE data cable, set your jumpers for cable select.

A motherboard typically has a built-in primary and secondary controller (interface). A ribbon cable with a red stripe that represents pin 1 connects the hard drive and an optional device, such as a second hard drive or CD-ROM, to the motherboard’s primary IDE controller. Your primary master hard drive should be attached to the connector at the far end of the ribbon cable. When connecting the data cable to the hard drive, make sure that you match pin 1 on the adapter to pin 1 on the hard drive. The slave device should be connected to the middle connector. And finally, attach the other end of the data cable to the motherboard’s controller, verifying again that pin 1 on the cable matches pin 1 on the controller. The secondary controller can be used to connect two more devices to the motherboard. If you are only using the primary controller to connect devices, you can disable the secondary controller in the BIOS to free up IRQ 15 for other peripheral devices. The first device attached to the secondary controller is known as the secondary master. The second device attached is called the secondary slave.

Note

If you install a second device to an IDE interface, such as a hard drive, and the operating system is plug and play, the operating system will automatically assign a letter designation to the new device.

If you are installing two new hard drives on the same IDE channel, you need to configure one to be the master drive and one to be the slave drive. If you reboot and the slave drive is not recognized by the system BIOS, you should test the slave drive by configuring it to be the master drive, remove the original master, and reboot the system. This will tell you if you have an incompatible or bad drive.

Note

If you notice that a hard drive’s LED light indicator is constantly lit or pulsing, this is a sign that you need to install more memory.

Following are the basic steps to installing a hard drive:

1. Unplug the power cord that is connected to the back of the computer. Put on your antistatic wrist protector.
2. Remove the screws or clips that attach the computer’s case to the system unit itself.
3. Determine whether the hard drive will be installed as a master or a slave device and make the necessary jumper changes on both drives to reflect your decision.
4. Plug one end of the data cable into the hard drive. Ensure that pin 1 on the data cable matches pin 1 on the drive. Plug the center connector into the slave drive if required. Plug the other end of the ribbon cable into the motherboard, also matching pin 1 of the cable to pin 1 on the motherboard’s controller.
5. Connect an available system power connector into the hard drive’s power socket. Do the same for the slave drive if using a slave drive.
6. Anchor the hard drive or drives into an open drive bay with screws.
7. Replace the system unit’s cover. Take your wrist strap off. Plug the computer’s power cord back into the system. Power the computer on.
8. If the CMOS hard drive settings are set to auto-detect, the hard drive or drives should be detected for you. If not, you will have to manually set the drive’s geometry, including the number of cylinders, sectors, and heads, in the CMOS settings.
9. Partition and format the drive or drives if no operating system is present.