| Back of an IDE or ATA drive. The master/slave jumpers are just to the right of the ribbon cable connector (the far-right connector [a Molex connector] is the power connector). |
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Integrated Drive Electronics (IDE) hard drive were the successor to
ST-506-type drives.
Before ATA drives, the BIOS limited the drive size to 504 MiB. This is because the BIOS could only access a maximum of 1,024 cylinders, 16 heads, and 63 sectors. With 512 bytes per sector, this added up to 528,482,304 bytes. To convert this count to MiB, we must divide it by 1,024 twice (MiB are counted in powers of two, so 1 MiB is 1,024 x 1,024). That gives us 504 MiB. This limitation could be bypassed by special drivers such as Seagate's EasyBIOS or Western Digital's EZ-Drive. Such BIOS extensions resided on the otherwise-unused part cylinder 0 and were loaded by the Master Boot Record.
IDE drives used a 40-pin ribbon cable with one or two drives per cable.
Configured by one or more jumpers
An IDE or ATA drive can be either device 0 or device 1. Device 0 and Device 1 are usually called and labeled "master and slave" respectively. However, the "master" has no control over the slave and no higher priority. You can have a master with no slave on one cable, but to have a slave, you must have a master, too (some later BIOSs allow a slave alone, but don't count on it).
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The following are some available master/slave configurations:
Single/Master (MA)
Single and master mean the same thing.
Master with slave
Some drives require this setting when both a master and slave are on the cable.
Slave (SL)
If the drive is a slave, there must be a master on the cable, too.
Cable Select (CS [ATA only])
Drive cables may have pin 28 disconnected (the wire clipped) to allow the cable select function. When using the cable select configuration, the drive at the end of the cable is the master, and the drive in the middle is the slave.
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The hard drive mounting screww is a short, coarse thread screw, no flange. The screws used to mount a hard disk are usually like the one pictured above. However, any screw with the same thread will do (such as case screws and newer motherboard screws) if the screw isn't too long, resulting in contact with the circuit board in the drive.
Holding the drive in its bay with a single screw is common practice. This is not recommended for computers built for retail sale or computers repaired for the general public. However, this is a considerable labor saver in an environment where you support many computers.
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The red stripe on the ribbon cable is always next to the power connector.
Pin one rule:
Red stripe to pin one.
ST-506-type drives and IDE/ATA drives used a four-pin Molex connector for power. This connector is keyed, so it is difficult to attach incorrectly. However, the Molex connector may be difficult to push into place or remove.
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This is usually automatic. Older systems required the technician to specify the geometry of the drive.
Geometry
Cylinders, Heads and Sectors (CHS)
Usually specified on the drive label.
LBA mode
Required to access more than 512 MB
Obsolete with the later drives.
Now called PATA (parallel ATA)
Two channels (i.e., two cables, like IDE)
Primary and secondary channels
Two drives per
channel (4 drives total)
Each channel can have one master and one slave
ATA Packet Interface
Standard for ATA CD-ROM or
DVD-ROM
If you have a single ATA hard drive and a single ATA CD-ROM or DVD-ROM, putting CD/DVD-ROM on a separate channel from a hard disk is considered best practice. According to Wikipedia, this is a myth, but they don't support this statement. If the CD/DVD-ROM is busy (doing a lot of input, like when watching a movie), it will tie up the channel because it is slower than a hard drive, and only one device can communicate on the cable simultaneously.
Ultra Direct Memory Access
Blue connector on the
motherboard
80 wire cable (as opposed to 40)
" The data wires are separated by ground wires to
reduce crosstalk
" 80-wire UDMA cables are notably thinner and stiffer than
40-wire cables.
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Same as IDE
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