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Question about regular USB speed

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Old 03-26-03, 12:02 PM Thread Starter   #1
DDR-PIII
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Question about regular USB speed


I've got an external CD-RW and it connected to the computer VIA a USB port, but it's limited to 4x when writng/re-writing, it says when using a USB connection anything higher than 4x or 700kb/sec it wouldnt write very stable, so I'm just wondering how fast is USB 1.0 ? is that what it's called ?
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Old 03-26-03, 12:22 PM   #2
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Hi,

My undestanding is that USB 1.0/1.1 works at 12 Mbps (read Megabits/second) speed. But in reality and due to protocol/packing overheads, you can not expect to reach more than 0.8-1 MBPS (Megabytes/second) sustained transfer rates.
Given that a 1x CDROM speed is 150KBPS, then 0.8/0.15 = 5x approx the maximum reachable reliable speed, which is more or less what you pointed out.

If USB 2.0, then we're talking about 480 Mbps... a completely different animal, being able to easily sustain 33MBPS (UDMA2) speeds.

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Old 03-26-03, 01:19 PM Thread Starter   #3
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Quote:
Originally posted by FTC
Hi,

My undestanding is that USB 1.0/1.1 works at 12 Mbps (read Megabits/second) speed. But in reality and due to protocol/packing overheads, you can not expect to reach more than 0.8-1 MBPS (Megabytes/second) sustained transfer rates.
Given that a 1x CDROM speed is 150KBPS, then 0.8/0.15 = 5x approx the maximum reachable reliable speed, which is more or less what you pointed out.

If USB 2.0, then we're talking about 480 Mbps... a completely different animal, being able to easily sustain 33MBPS (UDMA2) speeds.

Regards
FTC
Ok, thanks, I'm currently just using my legacy USB "on-board" which is 1.0/1.1, If I were to buy a 2/4 port USB 2.0 for my PCI slot would it allow me to write faster ? or would it still be limited by the CD-RW's firmware ?
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Old 03-26-03, 01:31 PM   #4
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the Writer has to be made for USB 2.0 to use it
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