PA-RISC Visualize Workstation Universal Serial Bus

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USB Alternatives
Attribute USB IEEE-1394 async SCSI sync SCSI
Ports per host Open (2 typ.) Typ. 1…4 Open (1 typ.) Open (1 typ.)
Pin count
4 6 50 50 or 68
Cable segment
length
5m 4.5m 6m
(single-ended)
varies
Max. transparent distance
30m 72m Unlimited w/repeaters Unlimited w/repeaters
Topology
Tiered-Star Tiered-Star Parallel Bus Parallel Bus
Device-to-Device I/O?
No Yes Theoretically Theoretically
Hot attach/detach
Yes Yes No No
Device power
Bus or Local Bus or Local Local only Local only
Power available
100 to 500 mA
per port
1.5 A / port N/A N/A
Power management
Yes Yes Only recently Recently
Devices/port controller
127
63
a
a. Bus-to-bus bridges permit transparent access to over 60,000 nodes.
77 or 15
Device enumeration
All All Mostly Usually
Peak transfer rate
1.5 MB/s 50+ MB/s 1.5 MB/s 80 MB/s
Error control
CRC CRC Parity Parity
Flow control
Packet re-send Packet re-send Handshake Handshake