Server+ Practice Questions

SCSI Bus Width

Home Up Next

Q1.Which of the following are true about Ultra 640 SCSI? [Choose 2 best answers].

A. Maximum transfer speed of 640Mbps

B. 16-bit bus

C. 8-bit bus

D. Maximum transfer speeds of 320 MBPS

Correct Answer: A,B

Explanation:

SCSI Type	Transfer speed	bus
SCSI-1	5Mbps	8 bit bus
Fast Wide SCSI 2	20Mbps	16 bit bus
Ultra Wide SCSI 3	40Mbps	16 bit bus
Ultra 2	40Mbps	16 bit bus
Ultra2 Wide	80Mbps	16 bit bus
Ultra 3	160Mbps	16 bit bus
Ultra320	320Mbps	16 bit bus
Ultra640	640Mbps	16 bit bus

Device support:

Most older specs: SCSI ID - 0=bootable drive, 7=controller, 1-6=any other devices

SCSI 3 ultra-wide, Ultra320, Ultra640: 16 devices, 0=bootable drive, 15=controller

Internal parallel SCSI cables have two or more 50, 68, or 80-pin connectors attached. External cables have 50 or 68-pin connectors at each end, depending on the specific SCSI bus width supported.

The figure below shows the connectors configuration for 80-pin SCA (Single Connect Attachment):

All of these SCSI types are parallel -- bits of data move through the bus simultaneously rather than one at a time. The newest type of SCSI, called Serial Attached SCSI (SAS), uses SCSI commands but transmits data serially. SAS uses a point-to-point serial connection to move data at 3.0 gigabits per second, and each SAS port can support up to 128 devices or expanders.

All the different SCSI varieties use controllers and cables to interface with devices

Note that older types were given for understanding purpose and you are unlikely to get any question on older SCSI types, such as SCSI-1, and 2.

Home Up Next