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.
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