Small Computer
System Interface
Small Computer System Interface
➢ The Small Computer System Interface is
a set of parallel interface standards
for attaching disk drives, printers,
scanners and etc to the computers.
➢ It’s a drive interface standards that
had been around as long as the earliest
ATA standards.
➔ Larry Boucher is considered as “Father
of SCSI”.
HISTORY ➔ SCSI is derived from “SASI- Shugart
Associates System Interface”, developed
circa 1978.
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INTERNAL SCSI
➢ Internal SCSI devices are installed inside the
pc & connect to the host adapter through the
internal connector.
EXTERNAL SCSI
➢ Multiple internal devices can be connected ➢ External SCSI devices are connected to the host
together by using a cable with more connector. adapter through the special SCSI external
connector of the host adapter.
○
➢ All external connection have two connection it
the back to allow for daisy chaining of multiple
external devices
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EXTERNAL SCSI
INTERNAL SCSI
➢ A SCSI host adapter is a device used
to connect one or more other SCSI
devices to a computer bus. SCSI HOST ADAPTER
➢ It is commonly called as SCSI
controller, which is not connected to
SCSI protocol.
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TYPES OF SCSI
SCSI 1 (NARROW SCSI)
SCSI 2
SCSI 3 (ULTRA SCSI)
SCSI 1 (NARROW SCSI)
➢ It's used 50 pin cable with maximum
transfer rate 5 MBPS & it used 8 bit
bus. Max 8 devices
➢ It’s used 25,50 or 68 pin cable with a
transfer rate of 10 MBPS.
SCSI 2
➢ It’s originally used 8 bit bus but an
enhancement fast wide SCSI that uses
16 bit bus & 16 devices at 20 MBPS.
SCSI 3
➢ It uses 50, 68 or 80 pin cable & the
common cable is 80 pin single
connector attachment (SCA).
➢ It’s also called Ultra SCSI. also used
in 16 devices.
Types Speeds (MBPS) Speeds (GBPS)
Ultra 160 160 mbps 1.28 gbps
Ultra 320 320 mbps 2.56 gbps
Ultra 640 640 mbps 5.12 gbps
SCSI ID
➢ SCSI devices are controlled by SCSI controller each devices
including the controller is assign SCSI ID using number 0-15.
➢ The controller is normally assigned the highest priority SCSI
ID of 7, it is used as controller ID.
DAISY CHAINING
➢ SCSI Designs are connected together in a daisy chain fashion,
which indicates are devices are connected each other likes
links in a chain state of been connected directly to a central
devices.
➢ Each devices has two connector to support daisy chain
connection.
➢ Additionally the last device the chain must be terminated, so
that the controller know that there are not any additional
devices in the chain.
Terminator
ADVANTAGES
● Its performance is much faster than IDE or SATA.
● Many devices(nearly 16) can be attached at the same
time on a single controller.
● The interfacing for different types of devices is done
through the same cable.
● The devices of same type have common characteristics
so it's easy to replace the old devices.
● The devices are independent so the computer can do
other work.
DISADVANTAGES
● The SCSI drives and hardware are more expensive
than IDE or SATA.
● It may be difficult to configure older models.
THANK YOU ABDUL SAMI (A.K.A 106_Sam)
Cyber Security Researcher,
Any Questions ?
