D ISCOVERING IDE D EVICES

IDE OVERVIEW The hard drive controller is responsible for converting signals made by the system CPU to signals that the hard disk can understand. These signals include instructions on where to find data and how to get to that data. The hard disk performs its task, and any data that needs to be returned is sent to the controller from the hard disk. The controller then converts the signals from the hard disk into signals that the system can understand.

IDE OVERVIEW In the past, the controller was on an expansion card, which was connected to the drives via ribbon cables. The goal of IDE was to make the installation of hard disks easier by including the controller on the hard disk, which is where the name comes from: Integrated Drive Electronics (IDE). Originally, IDE was available only in the flavor of hard drives; you did not have any other type of IDE device, such as CD-ROM or tape drives. IDE hard drives had a maximum capacity of about 528MB. Back in the day when IDE was first used, SCSI was better in that respect because it supported eight devices in a chain.

IDE OVERVIEW Original IDE devices have a transfer rate of about 10 Mbps and may have cache on the drive itself. Cache memory is a small amount of memory for storing data frequently used to increase drive performance. Because of its limitations, IDE has been replaced by Enhanced Integrated Drive Electronics (EIDE). EIDE devices have a transfer rate of about 16 MBps. Four devices are allowed in an EIDE chain, with a greater variety available. Note that the capacity of the drives has been dramatically increased with EIDE — it now supports drives of over 200GB

IDE OVERVIEW

IDE/ATA STANDARD A number of hard drive standards have been developed over the last two decades, the first major standard being the IDE standard. The IDE standard, which has been around since 1989, calls for an integrated controller on the drive to manage information entering and leaving the hard disk. IDE drives attach to the motherboard by means of a 40- wire ribbon cable. The IDE standard also allows two drives to daisy chain, creating a master/slave relationship between devices. The master drive is responsible for sending and receiving information in the chain The IDE standard is also known as the Advanced Technology Attachment (ATA) standard, sometimes called the ATA-1 standard.

IDE/ATA STANDARD IDE refers generically to any drive interface in which the controller is built into the drive, whereas ATA refers to the specific implementation of IDE that is used in most PCs. ATA refers to either just the parallel version or both the parallel and serial versions, whereas Parallel ATA (PATA) refers specifically to the parallel version and Serial ATA (SATA) refers specifically to the serial version.

EIDE/ATA-2 STANDARD The EIDE standard allows four drives to be connected to a dual-channel controller. This is usually implemented as a motherboard with two connectors (also known as controllers) — one primary and one secondary. You could then connect two drives off of each controller, making a master/slave chain for each controller. EIDE also supports larger hard disks than the original IDE standard; the original size of an IDE drive was approximately 528MB. The EIDE standard is also known as ATA-2 standard.

ATAPI SPECIFICATION Originally, IDE devices were implemented as hard drives, but an additional ATA specification allows other types of devices to exist on an ATA (or IDE) chain. This specification is the ATA Packet Interface (ATAPI), which allows devices like CD-ROMs and tape drives to exist on an ATA chain. Other types of ATAPI devices are CD writers, DVD devices, and Zip drives.

U LTRA DMA Ultra DMA drives have two major benefits over ATA drives: Speed: Originally, Ultra DMA devices functioned at twice the speed of regular IDE devices. IDE devices execute commands at 16.6 Mbps, whereas Ultra DMA devices execute commands at 33.3 MBps, or 66.6 MBps with ltra DMA/66. Note that there have been improvements to Ultra DMA to include speeds of 133 MBps. Reliability: Ultra DMA devices implement error correction, which provides for increased data reliability compared with IDE, which does not implement error correction.

U LTRA DMA Ultra DMA technology is backward compatible with IDE and EIDE. Ultra DMA/66 requires the use of an 80-wire ribbon cable, which contains the normal 40 wires of an IDE cable plus an additional 40 ground wires to reduce noise on the cable and thus increase performance. The 80-wire cable still uses a 40-pin connector on the end to keep compatibility with IDE.

D RIVE PERFORMANCE The performance of the drive is determined by the Programmed I/O (PIO) mode or DMA mode it supports. The PIO mode or DMA mode is a protocol that determines the transfer rate of the drive.

P RECURSORS TO IDE

PATA AND SATA C ABLE

SATA Development for Serial ATA started when the Serial ATA Working Group effort was announced at the Intel Developer Forum in February The initial members of the Serial ATA Working Group included APT Technologies, Dell, IBM, Intel, Maxtor, Quantum, and Seagate. The original group later became known as the Serial ATA II Working Group, and finally in July 2004 it became the Serial ATA International Organization.

SATA The following SATA specifications have been released by these groups: The first Serial ATA 1.0 draft specification was released in November 2000 and was officially published as a final specification in August The first Serial ATA II Working Group extensions to this specification, which made Serial ATA suitable for network storage, were released in October SATA Revision 2 was released in April It added the 3Gbps (300MBps) signaling speed. SATA Revision 2.5 was released in August In addition to 3Gbps signaling, it added Native Command Queuing (NCQ), staggered spin-up, hot plug, port multiplier, and eSATA support.

SATA SATA Revision 2.6 was released in March It added new internal Slimline and Micro cables and connectors as well as modifications to Native Command Queuing (NCQ). SATA Revision 3.0 was released in It added the 6Gbps (600MBps) signaling speed.