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  1. #1
    Disabled DDR-PIII's Avatar
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    Feb 2002
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    6p6

    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 ?

  2. #2
    Member FTC's Avatar
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    Mar 2002
    Location
    Barcelona, Spain
    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
    AOpen s661FXM-FSN, PM "Dothan" 1.8 @ 2.61Ghz (1.66v),XP90 cooler, Sapphire HD3850 AGP. 2048MB uccc, WD Black 1Tb HDD. PLextor PX712A+PX760A
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  3. #3
    Disabled DDR-PIII's Avatar
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    Feb 2002
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    6p6
    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 ?

  4. #4
    Member Jeff7477's Avatar
    Join Date
    Feb 2003
    Location
    Lincoln, Ne
    the Writer has to be made for USB 2.0 to use it

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