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USB2.0 @ 480Mbps....is that so ??

Posted on 2002-03-30
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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 ?




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Question by:hhheng
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6 Comments
 
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Expert Comment

by:kannabis
ID: 6908492
Here is a spec for USB 2.0.  "40 times faster than the existing USB 1.1."  "The target speed of USB 2.0 is 480 Megabits per second (Mbs)"

http://www.intel.com/pressroom/archive/releases/us101299.htm

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Author Comment

by:hhheng
ID: 6909911
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

 
 
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Author Comment

by:hhheng
ID: 6909919
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


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kannabis earned 50 total points
ID: 6910511
you are getting confused with the Mbps and MBps. This should help you out...

"USB 2.0 will extend the capabilities of the interface from 12 Mbps, which is available on USB 1.1, to between 120-240 Mbps on USB 2.0, providing a connection point for next-generation peripherals which complement higher performance PCs. USB 2.0 is expected to be both forward and backward compatible with USB 1.1, and to result in a seamless transition process for the end user. USB 2.0 is expected to lead to the development of higher performance peripherals that will bring new applications to the PC. Due to these factors, USB 2.0 is expected to supercede USB 1.1, which is already a ubiquitous connector on PC platforms. The rev 0.9 specification is expected to be available in second half 1999. USB 2.0 systems and peripherals are expected in second half 2000.

USB 1.1's data rate of 12 Mbps, is sufficient for PC peripherals such as telephones, digital cameras, keyboards, mice, digital joysticks, tablets, wireless base stations, cartridge, tape, and floppy drives, digital speakers, scanners and printers. The higher bandwidth of USB 2.0 will permit higher functionality PC peripherals, including higher resolution video conferencing cameras, and next generation scanners, printers and fast storage units. The higher data rate of USB 2.0 will also open up the possibilities of new and exciting peripherals."

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Author Comment

by:hhheng
ID: 6911305
Thanks and cheers..
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Expert Comment

by:kannabis
ID: 6911598
glad I could help
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