Master/Slave Configurations
The hard drive or CD-ROM drive controller’s function is to receive commands to the drive and control the action of the drive itself. The technology incorporated in IDE and ATA devices allows one controller to take over the function of more than one drive. This means that you can install up to two drives on a single ribbon cable. This setup is called a master/slave configuration because one drive’s controller directs the activities of both drives. It is important to note here that most computer systems can support a mixture of IDE and ATA drives.
Installing Master and Slave Hard Drives
1. Determine, which drive, will be the master. (See the “Choosing a Master” From the Classroom for more information).
2. Locate the master/slave jumpers, which can be found on the bottom of the drive or, more commonly, on the end by the power and ribbon cable connectors. In Fig 2-1, the jumpers are located to the left of the power connector and the jumper settings are indicated by the standard settings information on the label.
Fig 2.1 the master/slave jumper set on a typical hard drive
3. Use the drive label information to determine which jumper settings to use for a master or a slave configuration.
4. Set this drive as a master using the jumper(s).
5. Using the procedure explained in Chapter 1, Exercise 1-2, physically install this drive on the end of the ribbon cable and secure it to an available drive bay.
6. Using the proper jumper setting, configure the second drive as a slave.
7. Install the second drive in the middle of the ribbon cable. Your hard drive setup should look similar to the one shown in Fig 2-2. Note the position of the hard drives on the ribbon cable.
The jumpers inform the BIOS about the IDE devices if they are master, slave or cable select. If a device is jumpered as cable select and if it is put in the farthest end from the controller then that device is recognized as master and if it is put in the middle of the cable it is recognized as slave. Whereas for Master and Slave configurations wherever the device is put it is recognized as master or slave. The jumpers vary for different manufacturers and are not the same. Seagate is the only manufacturer whose hard disk when not jumpered is recognized as Slave.
Note: The master drive must be set to the master jumper setting and be installed on the end of the ribbon cable. The slave drive must be set to the slave jumper setting and be installed in the middle of the ribbon cable
Most newer computers will detect the presence of a master/slave configuration and name the drives appropriately: Typically, the master will be drive C, and the slave will be drive D. However, some older computers require you to perform drive detection. In this case, when you start the computer, enter the CMOS settings program, as discussed in Chapter 1. Select the Auto-Detect or Detect Hard Drive option (these options might have slightly different names on different computers). This choice forces the BIOS to search all drive controller connections for the presence and configuration of hard or CD-ROM drives.
Fig 2.2 The finished installation of a master/slave configuration
Devices per Channel
Most newer computers have two hard drive controllers. That is, the motherboard has connectors for two ribbon cables (see Fig 2-3). These controllers are termed primary and secondary. If there is only one drive present, it must be attached to the primary controller. An additional drive can be added as either a primary slave or a secondary master. It is important to note that although they are often referred to as hard drive controllers, these devices are not limited to controlling hard drives; they are also used to control CD-ROM drives.
To add a drive to the secondary controller, simply connect the drive to a ribbon cable and attach the ribbon cable to the secondary controller port on the motherboard, ensuring that the red stripe is aligned with pin 1. You will also of course need to connect a power cable to the drive. There is usually no noticeable performance advantage to configuring a second drive as a secondary master rather than as a primary slave. (See the “Choosing a Master” From the Classroom for a discussion on choosing the master or slave designation.)
As before, the primary master receives the first available drive letter, typically C. The remaining drives are lettered according to this order of priority: primary slave, secondary master, and primary master.
When you add or remove a drive to or from a multidrive system, the drives are automatically relettered so that no letters are skipped. For example, suppose a system includes drives C: , D:, and E:. If drive D: is removed, the E: drive will be relabeled D: the next time the computer is started. Windows operating systems also allow for a drive to be configured to hold a certain drive letter.
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Choosing a Master
How do you determine which drive should be the master and which should be the slave? In many cases, it doesn’t matter which is which. That is, there is no real performance difference between master and slave drives. However, as with most computer configurations, there are some exceptions.
Some operating systems require that the hard drive containing the OS be configured as a master. This is important to note only if you are installing drives that already contain data. If you are installing new hard drives, you don’t have to worry about this; simply load the OS on the master drive after the drives are installed.
When using a mixture of old and new hard drives within the same system, set the newer drive as the master and the older drive as the slave. This setting is a good idea because newer drives can recognize and communicate with older drives, but the reverse isn’t true. An older drive’s controller will typically be unable to control the newer drive.
When using a hard drive and CD-ROM drive together in a master/slave configuration, always set the hard drive as the master and the CD-ROM as the slave because the CD-ROM’s controller is unable to take control of the hard drive. Additionally, some (but not most) CD-ROM drives are designed to work as slaves, even when there is no master present, and they simply cannot be configured as master drives.
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