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Drive Interface can be broadly classified into two types. Although each type can have sub-classifications based on minor improvements, the two main types can be identified as ‘Integrated Data Electronic’ (IDE) and ‘Small Computer System Interface’ (SCSI). SCSI devices may require a separate controller and host adapter card to activate the read and write functions. SCSI was developed after the realisation that traditional IDE interface or even ‘Ultra Direct Memory Access’ (UDMA) interface was not fast enough to move huge amounts of data, that are typical when managing multimedia files and processing data on high-end servers. IDE drives are standardised with ‘40 Pin’ connectors, functions and timings of signals and cable specifications to arrive at a compatibility factor for a wide range of IDE interface system buses. Commonly, there are 2 types of IDE interfaces, ‘ATA 1’ known as ‘Integrated Data Electronic’ (IDE) and ‘ATA 2’ known as ‘Enhanced Integrated Data Electronic’ (EIDE). Disk drives have to be absolutely compatible with the drive interface. An IDE type drive cannot be installed onto an MCA bus system. IDE drives have the drive controllers built into the physical body of the disk itself. Each controller corresponds to one physical drive on the system. Logical partitions on the same physical disk are treated as one controller drive. Controllers are special embedded circuitry, which facilitate specific type of data transfers while talking to the device. ‘Direct Memory Access’ (DMA) is a technique for transferring blocks of data directly into system memory thus avoiding complete interaction with the main processor. The motherboard has to have support for DMA data transfer to take place. Some adapters use a technique called ‘Programmed Input/Output’ (PIO), which is faster than DMA transfers in most cases, especially if the motherboard BIOS and device support block-mode PIO. ‘Bus Mastering’ is another technique, which takes control of the bus and can override the DMA controller circuitry of the motherboard to perform faster DMA transfer. Thus transfer can exceed the performance of block-mode PIO, and therefore is relatively more expensive proposition. The motherboard has support for bus mastering. Hard disk drives use either IDE interface or SCSI interface. Compact disc drives use either ‘Advanced Technology Attachment Packet Interface’ (ATAPI) with IDE interface or SCSI interface. Floppy disk drives use the IDE interface and are never manufactured via the SCSI interface. The ‘40 Pin’ data connector cable is used to connect IDE hard disk drives and compact disc drives.