Eide Master/Slave

EIDE is Enhanced IDE, a newer version of the IDE mass storage device interface standard. It evolved into the ATA/33 specification, then to ATA/66, ATA/100, and the recent revision is Ultra ATA/133. The number associated with the ATA specification indicates the peak data transfer rate. The Ultra ATA/133 can transfer data at a maximum rate of 133 MB/s. The next generation ATA is the Serial ATA. Its features include a peak data transfer rate of 150MB/s, thin cables for easy routing, improved cooling inside a system unit, and hot-pluggable connectors.

The EIDE interface provides a set of two IDE (Integrated Device Electronics) ports.  One is referred to as the primary port, the other as the secondary.  Each port attaches to a cable containing two plugs, and each plug can connect to a device. Thus, a total of four devices can be accommodated: two on the primary, and two on the secondary.  To distinguish between devices on the same IDE port, one device is considered the master, the other the slave, resulting in the following designations:  primary master, primary slave, secondary master, and secondary slave. 

When only one device appears on a port cable, it is not usually necessary to specify it as a master or a slave.  When two devices appear on a port cable, one needs to be assigned as the master, the other as the slave.  These assignments are usually made by setting a switch (also called a jumper) on the drive or using cable select. In older systems, the device must then be added to the machine's configuration information through a dialog with the machine's setup program.  The user may need to consult the machine's documentation to learn how to enter its setup program. Usually pressing F2, ESC, or DELETE (for Pentium machines running Windows) at the start of a reboot will cause a machine to enter its setup program instead of loading the operating system. However, most of the newer systems can automatically detect the added device and configure it accordingly.

EIDE devices usually expect a particular master/slave designation and come ready to assume that role.  Consult the documentation for each device to discover where it expects to reside.  If it must be connected to a location different than it expects, the device itself may have to be reconfigured.   Again, consult the device's documentation to learn how to do this.

2.3.2 Mass Storage

• How Mass Storage Devices Differ from RAM

• Disk Drive Reliability

• Optical Media: CDs versus DVDs

• Magnetic Media

• Optical versus Magnetic

• Solid State

• Comparing Storages

How Mass Storage Devices Differ from ram

Mass storage devices (magnetic disks, optical disks, and magnetic tape) have slow access times and low transfer rates. They are also located far from the processor. These mass storage devices are not even on the motherboard. (Sometimes they are not even in the same box as the motherboard!) But, mass storage technologies also have several important advantages:

• They are nonvolatile—meaning that information is not lost when power is turned off.

• They have huge capacities, measured in billions or even trillions of bytes.

• Their cost per bit stored is far lower than RAM.

• In some cases, they use removable media that can be popped into a drive, used as needed, and then taken out of the drive, or mailed to a friend. Several newer removable disk technologies have appeared since the 3.5-inch floppy (1.44 MB). The Iomega Zip drive uses removable disks with capacities of 100 to 750 MB, and the CD Read/Write drive uses writable optical disks with 650 MB or 700 MB of storage capacity. These days, the compact flash drives (also called thumb drives) which plug into USB ports have taken over the duties of the floppy or Zip drives. The memory capacity of these flash drives range from 128 MB to 16 GB. On the higher end, we now have external hard drives with 1 TB storage capacity. These types of drives are currently popular for making backups of a system's main hard drive, or for transferring large data files from one site to another. On the optical side, we now have dual layer writable DVD disks which have a storage capacity as high as 17GB. As hard drive capacity increases and optical disk technology matures, creating backups on external hard drives and re-writable optical disks has become a popular alternative.