CompTIA+ Installing IDE & SCSI Devices

Introduction Hard disks are larger, faster, and more reliable storage devices as compared to floppy disks. Hard disks have changed in their shape, size, and storage capacity ever since their introduction with the IBM-compatible PCs.Today, the standard hard disk can store and retrieve enormous data much faster than the hard disks used a decade ago.A computer system uses hard disks as the primary storage device for storing the operating system, applications, and data. Typically, a hard drive failure is the most traumatic event that can occur on a computer. If the hard disk crashes and the data are not backed up, the data is lost forever.Currently, the two most widely used hard disk technologies are IDE and SCSI.This tutorial covers the various IDE and SCSI options and configurations

IDE Interfaces

An Integrated Device Electronics (IDE) interface is used to connect Mass Storage media devices to the computer. These devices store large volumes of data. Some examples of this are Hard Disk, CDROM etc. This is the most common interface being used and is actually called ATA (Advanced Technology Attachment). IDE also refers to any device with the controller built-in.Most of the disks today are IDE and these disks have built in controller. They can be plugged into a bus connector on the motherboard or an adapter card. Due to the fact that the controller is on the drive itself, these disks are easy to install and require a minimum number of cables. The short signal pathways improve reliability of the disks.In the actual sense, ATA IDE is a much broader term than what we usually use. Most of the time, this is being referred to, just because this is the most popular interface. There are other types, like MCA IDE and XT IDE.

EIDE The next generation of IDE interface developed by Western Digital and used on IBM compatible computers are EIDE (Enhanced IDE). It is also referred to as ATA-2, Fast ATA or Fast IDE. Features of EIDE are:

• It supports data rates in the range 4 and 16.6 MBps and supports disks up to 8.4GB.
• It supports PIO Modes 3 and 4 and DMA modes 1 and 2.
• It supports four devices that are handled by two channels wherein each of these two channels are capable of supporting two devices that are in a master/slave configuration.Generally, the primary port is connected to a local bus. The address and the IRQ setting is similar to that of a standard IDE system that ensures backward compatibility with the other IDE systems thereby preventing conflicts.

Some of the advantages of EIDE are given below :

1. ATA-2 Enhancements : This is inclusive of all the improvements defined as part of the ATA-2 standard, including the higher-speed transfer modes.
2. ATAPI : This includes support for non-hard-disk ATAPI devices on the IDE/ATA channel.
3. Dual IDE/ATA Host Adapters : This standard specifically includes support for dual IDE/ATA channels, allowing the use of four IDE/ATA/ATAPI devices.

ATA / ATAPI ATA (AT Attachment) and ATAPI (ATA Packet Interface) are the actual names of the mass storage device interface that is often called the IDE and EIDE interface. The word AT is derived from PC/AT the third generation Computer from IBM.Starting with the original PC/AT hard disk, the evolution of ATA/ATAPI interface spans over a period of 20 years. ATA/ATAPI-7 is the current technology and research is in progress on ATA/ATAPI-8. Commonly used to connect the IBM compatible computers to the hard disks, CD ROM's and various other types of disks, the ATA interfaces are the most widely used interface today. Compatibility exists between each ATA standards, which allows a new ATA drive to be used in a computer that might be using an older or earlier ATA specification.ATA / ATA-1 / IDEATA was first introduced and developed by the Control Data Corporation, Western Digital, and Compaq.

• The ATA-1 uses an interface that is 8-bit or 16-bit.
• It possesses a transfer rate of up to 8.3MBps.
• It also supports PIO modes 0, 1, and 2.

However, ATA / ATA-1 interfaces are currently obsolete

ATA / ATAPI (Cont...) ATA-2 / EIDE / Fast ATA / Fast IDE / Ultra ATAATA-2 is often referred to as EIDE and at times the Fast ATA or Fast IDE was a standard that was approved in 1996 by ANSI. It was during this time that ATA-2 introduced the new PIO modes of 3 and 4.

• It is characterized with a transfer rate of up to 16.6 MBps.
• It supports DMA modes 1 and 2and LBA support.
• It also supports disks up to 8.4 GB.

ATA-3 / EIDEThis is also a standard that was approved in 1997 by ANSI. Additional security features and also the new S.M.A.R.T feature are provided in this.ATA-4 / ATAPI-4 / ATA/ATAPI-4In 1998, ANSI approved ATA-4. This included the ATAPI packet command feature and introduced UDMA/33 also known as ultra-DMA/33 or ultra-ATA/33 that supported data transfer rates of up to 33 MBps.

ATA / ATAPI (Cont...)

ATA-5 / ATA/ATAPI-5A standard that was approved by ANSI in 2000 was ATA-5. This added support for Ultra-DMA/66 that supported data transfers of up to 66MBps. It was also capable of detecting between 40 or 80-wire cables.ATA-6 / ATA/ATAPI-6In 2001, ANSI approved ATA-6. This had additional support for Ultra-DMA/100 with a transfer rate of up to 100 MBps.

ATA / ATAPI (Cont...) ATAPIAn extension of ATA is ATAPI. Apart from the hard disk disks, it offers support to devices like the CD-ROM, Tape disks and other computer peripherals. This was altogether a separate standard from ATA before releasing ATA-4 or ATA/ATAPI-4. It includes CD-ROMs, CD-R, CD-RW, DVD, Tape disks and some super-floppy disks such as ZIP and LS-120.

Serial ATA (SATA) Serial Advanced Technology Attachment (SATA) is also popularly known as Serial ATA or S-ATA.

• SATA is a computer bus used to transfer data to and from a hard disk.
• It is a successor of the Advanced Technology Attachment standard (ATA).
• The older technology is now known as Parallel ATA (PATA) which distinguishes it from Serial ATA disks.
• Unlike IDE, which uses parallel signaling, SATA uses serial signaling technology, which makes these cables thinner than the ribbon cables used by IDE hard disks.
• The SATA cables can also be longer thereby permitting you to connect to more distant devices without worrying about signal interference.
• It is capable of transferring the data at 150Mbps.
• SATA replaces the old 40 pin ATA plug and 80 wires ATA cables with simple thin cables that have only seven wires.

The way ATA cable operates is that it assigns one pin and wire to each bit, and with the use of same wire transmits data bi-directionally. However, Serial ATA makes use of two balanced (positive and negative) pair of wires that are devoted for transmitting bits in one direction. Its main feature is that it has a ground wire on both the outside edges along with one wire down the middle that helps in separating the signals moving in each direction. Protection is provided against interference by the ground wire.

Serial ATA (SATA) (Cont...)

Various types of SATA standards are as follows :SATA150First-generation Serial ATA interfaces, also reffered to as SATA150. It uses 8B/10B encoding at the physical layer resulting in an actual data transfer rate of 150 Mbps.SATA300With the release of the Nvidia nForce4 chipset in 2004, the maximum throughput has been doubled (increased) to 300 MB(s), which is very widely referred to as “Serial ATA II”.External SATAIn the beginning, SATA was designed as an internal or inside-the-box interface technology to bring out improved performance and added features to internal PC or consumer storage. Its success led the designers to design SATA outside the box too extending its features. External SATA or eSATA as it is commonly referred to, has a high performance when compared with USB or IEEE 1394 Interfaces. The shielded cables run upto 2 meters outside the box allowing it to connect or take advantge of SATA externally.Benefits of ESATA

• Up to 6 times faster than existing external storage solutions such as USB 2.0 & IEEE1394.
• Robust and user friendly external connection.
• High performance, cost effective expansion storage.
• Up to 2 meter shielded cables and connectors.

Master / Slave / Cable Select Configuring devices on an IDE Cable:

• Each disk has a set of pins at the back end and also a “jumper” which can be removed or attached to a pair of pins in order to close a circuit, and thus configure the hardware acoordingly. The instructions are generally provided on a label attached to the disk.
• It is possible to set jumper in such a way so as to inform the device to be a Master, a Slave, or a Cable Select.

Note: When the jumper is set to Cable Select, the device is capable of sensing that it is connected to the connector at the end of the cable and automatically becomes Master or when connected to the connector in the middle of the cable it automatically becomes Slave.

Master/Slave/Cable Select (Cont...) If you have decided to have two hard disks on your computer then:

1. Set the bootable as primary master and the other one as the secondary master.
2. Set your CD-ROMs as the secondary slave. CD-ROMs usually have four settings: Master, Slave, Cable Select, and Single Drive.

Here, the single drive is used only if it is the only device on the specific IDE channel. Therefore if you intend to have only one hard drive on a primary channel, you use single drive.

Device Per Channel As mentioned above, each IDE channel can support two devices, hard disks or CD-ROMs. For optimal performance it is recommend that you use only one device per channel. If on the other hand, saving an IRQ is more of a priority than optimal performance then you may rearrange your setup and put both devices on the primary channel, and disable the secondary channel.If you are using only the primary IDE channel on a system having a motherboard that contains two built-in controllers, then it is a must that you disable the secondary controller to free up the resources it uses. This is done by entering into the BIOS setup and looking in for the settings that control the IDE controllers, which are usually located in the "Integrated Peripherals" grouping. Once you locate this, disable the secondary IDE controller. You can refer to the settings indicated in the motherboard manual provided by the manufacturer.

Cable Orientation and Requirement While connecting IDE devices on to the computer it is important and necessary to remember that the Master and Slave devices are different for 80-wire cables and 40-wire cables. The 80 wire cable is always given to the Primary connection. Mostly the 40-wire cable is connected on other Secondary connections. This is usually where the lesser used devices like CD ROMs, CDROM Burners and Tape Disks are connected .The latest 80-wire cable has very small wires running from one connector to another. Conversely, the 40-wire cable has larger wires. The reason for this being the newer standard needs the addition and separation of the wires in order to achieve faster speeds.

Cable Orientation and Requirement (Cont...) 40-Wire CablesThe Master device, which is usually a CD-ROM or CD-ROM recorder / burner, still goes on the END, in the older 40-wire ATA cables. However, we need to set the jumpers as Slave. The Master for this 40-wire cable goes on the Middle connector. Problems may be faced only on older computers (the AT type) for which you should read the manual that came with the motherboard or contact the maker of the system.You might try it as a Master and there is a possibility that it may work but that's not the way it is to be done. Incase you want to use the cable select with the older drive on a 40-wire cable you should first consult the maker of the drive for the instructions (the instructions will be specific to the vendor).

Cable Orientation and Requirement (Cont...) 80-wire CablesOn an ATA66/100/133 standard 80-wire cable, the Master hard drive or the boot hard drive is placed on the END of the cable. When using Cable Select, the standard 40-wire ATA ribbon cable and the 80-wire cable give different drive behaviors.The three connectors have typically different colors and attach to specific items:

• The blue connector attaches to the motherboard.
• The black connector attaches to the primary or master drive.
• The gray connector attaches to the secondary or slave drive.

There is a stripe along one side of the cable, which indicates that the wire on that side is attached to Pin 1 of each connector and wire 20 is not connected to anything. Actually, there is no pin in that position. The main purpose of this is to ensure that the cable is attached to the drive in the correct position. Using a cable key was a method through which the manufacturers ensured that the cables were not reversed. Cable key is nothing but a small plastic square that's found on top of the connector on the ribbon cable that clasps onto a notch that's on the connector of the device thus allowing the cable to fix in only one position.