PC Hardware book
High capacity storage devices
Hard Drive hardware
Four types of hard drive interface have been used
with PC computers, first there was the ST506 Interface. This
interface used to be called the ST412 interface but this name was soon dropped
in favour of ST506. These names were the result of using the names of the first
commonly used compact Hard Drives.
ST506 Intervae Hard Drives
The cables used to connect the Interface card to the drive was a
single 34 wire cable that was daisy chained from one drive to the next,
and a 20 wire cable for each drive. These cables usually had edge
connectors on the Drive end.
Another early Hard Drive Interface called ESDI, also used
the same cable configuration as the ST506 Interface. It is not possible to tell
the difference between ST506 and ESDI hardware by sight.
The IDE Hard Drive Interface The third Hard Drive Interface used with
PC hardware was given the name, Inbuilt Drive Electronics (IDE). This interface
was first used on the last 286 based (AT) machines. This Interface uses a 40
wire cable with header connectors on the drive end.
The IDE Interface has undergone great changes and today the
Enhanced IDE standards provide an interface that is very fast is used
with CDROM Drives, Tape Backup Drives and High Capacity
Removable Media Drives. EIDE uses the same 40 wire cable configuration as
the original IDE Interface.
Last but not least, there is the SCSI interface, pronounced
SCUZZI. This interface has been used where very fast performance, or very large
drive size, is important. Today advances to the IDE specification (Enhanced IDE)
has meant SCSI is not as important as it once was for performance and drive
size. The SCSI interface is not specifically a hard drive
interface, it is a universal interface, and can used for
connecting tape back-up drives, some CDROM drives and some Optical Scanner
devices, to PC computers. It is also often used to connect High Capacity
Removable Media Disk drives.
Hard Drive Interface cards
PC/XT Hard Drive Interface
cards
The PC/XT type computer used an ST506 hard drive
interface to connect the Hard Drive to the computers bus. Here is a
PC/XT ST506 Hard Drive Interface card. This interface required two cables
between the interface card and the Hard Drive. The 34 wire cable was "daisy
chained" if two drives were fitted, and each drive required its own 20 wire
cable.
286 (AT) Hard Drive Interface cards
The first
PC/AT type computers used the ST506 Hard Drive
Interface, here is an ISA bus ST506 Interface card. This card also
provides a Floppy Drive Interface.
386/486 Hard Drive Interface cards
The IDE Interface was
first built on a simple card with a Floppy Disk Drive Interface. This interface
was far more simple than earlier Hard drive Interfaces. Most of the interface
electronics is on the actual hard drive, rather than on the Interface card. This
card was usually referred to as an IDE/FDC card or a paddle card.
In this era a typical PC Computer consisted of a System Board, a
Video card, an IDE/FDC card, and an SPG card. The SPG card provided
Serial, Parallel and Games Ports.
As more and more interfaces were put on a single card, the number of cards in
a basic PC computer was reduced to just two. The I/O card and the Video card.
The last generation of ISA bus I/O cards provide, Floppy Drive Interface, IDE
Hard Drive Interface, Serial Ports (usually two), Parallel Port and a Games
Port. These cards were often called, SPG/IDE/FDC cards. Unlike
the PC and PC/XT, the I/O cards used in AT and later PC type computers, do not
have a Real Time Clock, because this function is built into the System Board.
The last generation of 486 System Boards and Pentium System Boards
have the basic I/O functions and the Hard Drive and Floppy Drive Interfaces
built on the System Board.
CDROM hardware
Today most PC computers are fitted with a
CDROM Drive and a Sound card. Here are some photos of typical
modern CDROM drive hardware.
Early CDROM drives used either the SCSI Interface or one of four Proprietary
Interfaces designed by various manufacturers. Today the Enhanced IDE
Interface is the industry standard for CDROM Drives.
The most poplar, x86 Family
XT
Computers (8086)
80286
(16 bits Data Bus)
80386
(The First 32 bits Data Bus) (Compatible with Windows`95)
80486 (High Performance)
Pentium, 5x86
and 6x86 family
Anexos
Terminology Computer Glossary
Connectors
used with PC Computer hardware
Floppy disk drive
hardware
Storage devices
The PC busses
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Ciudad de la Havana - Cuba