hhheng
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USB2.0 @ 480Mbps....is that so ??
USB2.0 @ 480Mbps , is that so ...?
...not really. This is what I understand :-
USB2.0 does a "round-robin" query on its single channel to ensure a consistent, sustainable output of 12Mbps for every USB2.0 compliant device. If a USB1.1 type is detected, the 12Mbps will be stepped down to 1.5Mbps. It's doesn't matter if there are 8 or 1 device, the speed is still 12Mbps for USB2.0 and 1.5Mbps for USB1.1
So why USB2.0 = 480Mbps ?
...not really. This is what I understand :-
USB2.0 does a "round-robin" query on its single channel to ensure a consistent, sustainable output of 12Mbps for every USB2.0 compliant device. If a USB1.1 type is detected, the 12Mbps will be stepped down to 1.5Mbps. It's doesn't matter if there are 8 or 1 device, the speed is still 12Mbps for USB2.0 and 1.5Mbps for USB1.1
So why USB2.0 = 480Mbps ?
ASKER
Hi kannabis,
I got this piece of info from the USB.ORG weblink :-
<< USB Info: Frequently Asked Questions
Q1: How fast is USB?
A1: High speed USB products have a design data rate of 480 Mb/s. Full speed USB devices signal at 12Mb/s, while low speed devices use a 1.5Mb/s subchannel.>>
..why "..full speed devices signal at12Mb/s and not 480Mb/s.."
Cheers..
Heng
I got this piece of info from the USB.ORG weblink :-
<< USB Info: Frequently Asked Questions
Q1: How fast is USB?
A1: High speed USB products have a design data rate of 480 Mb/s. Full speed USB devices signal at 12Mb/s, while low speed devices use a 1.5Mb/s subchannel.>>
..why "..full speed devices signal at12Mb/s and not 480Mb/s.."
Cheers..
Heng
ASKER
Hi kannabis,
I found more info. Take note below USB speed is 12Mbits/s.
<< Q2: How does this compare to other connections used with PCs and workstations?
A2: Here's a quick list of the maximum transfer rates for various connections in megabits (Mb) and megabytes (MB) per second:
serial port: 115kbits/s (.115Mbits/s)
standard parallel port: 115kBYTES/s (.115MBYTES/s)
USB: 12Mbits/s (1.5MBYTES/s)
ECP/EPP parallel port: 3MBYTES/s
IDE: 3.3-16.7MBYTES/s
SCSI-1: 5MBYTES/s
SCSI-2 (Fast SCSI, Fast Narrow SCSI): 10MBYTES/s
Fast Wide SCSI (Wide SCSI): 20MBYTES/s
Ultra SCSI (SCSI-3, Fast-20, Ultra Narrow): 20MBYTES/s
UltraIDE: 33MBYTES/s
Wide Ultra SCSI (Fast Wide 20): 40MBYTES/s
Ultra2 SCSI: 40MBYTES/s
IEEE-1394: 100-400Mbits/s (12.5--50MBYTES/s)
Wide Ultra2 SCSI: 80MBYTES/s
Ultra3 SCSI: 80MBYTES/s
Wide Ultra3 SCSI: 160MBYTES/s
FC-AL Fiber Channel: 100-400MBYTES/s >>>
Cheers again..
Heng
I found more info. Take note below USB speed is 12Mbits/s.
<< Q2: How does this compare to other connections used with PCs and workstations?
A2: Here's a quick list of the maximum transfer rates for various connections in megabits (Mb) and megabytes (MB) per second:
serial port: 115kbits/s (.115Mbits/s)
standard parallel port: 115kBYTES/s (.115MBYTES/s)
USB: 12Mbits/s (1.5MBYTES/s)
ECP/EPP parallel port: 3MBYTES/s
IDE: 3.3-16.7MBYTES/s
SCSI-1: 5MBYTES/s
SCSI-2 (Fast SCSI, Fast Narrow SCSI): 10MBYTES/s
Fast Wide SCSI (Wide SCSI): 20MBYTES/s
Ultra SCSI (SCSI-3, Fast-20, Ultra Narrow): 20MBYTES/s
UltraIDE: 33MBYTES/s
Wide Ultra SCSI (Fast Wide 20): 40MBYTES/s
Ultra2 SCSI: 40MBYTES/s
IEEE-1394: 100-400Mbits/s (12.5--50MBYTES/s)
Wide Ultra2 SCSI: 80MBYTES/s
Ultra3 SCSI: 80MBYTES/s
Wide Ultra3 SCSI: 160MBYTES/s
FC-AL Fiber Channel: 100-400MBYTES/s >>>
Cheers again..
Heng
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ASKER
Thanks and cheers..
glad I could help
http://www.intel.com/pressroom/archive/releases/us101299.htm