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USB 2 Devices Not Necessarily High-Speed

Posted by timothy on from the words-by-any-other-names dept.

mgcsinc writes "Yahoo is running a story on how some manufacturers of "USB 2.0" devices are making hardware compatible with the USB 2.0 standard, but not necessarily its high-speed component." Sounds like the complaint raised earlier this year.

1 of 268 comments (clear)

  1. A lot of people fail to notice the real issue. by stvangel · · Score: 5, Interesting

    USB as well as FireWire are still a single set of wires. Unless you use some sort of USB router or multiple controllers, all the devices must share a finite amount of bandwidth based on the ratio of their speeds.

    For example: A device running at 2mb speed that sends 500kb in a second uses a full 1/4 of the entire USB bandwidth. This automatically chops the 12mb down to 9mb, and the 480mb down to 360mb. A 12mb device that sends 6mb cuts it in half.

    By the time you have a keyboard, mouse, joystick, mp3 player, external drive, and who knows what else sharing the USB connection, you have a lot of things competing for limited bandwidth with the slower devices taking an inordinate share of the pie. This is one of the reasons I like sticking to the old PS/2 style Mouse and keyboard connectors. Keep these usually slow devices from flooding the connection. Particularily the high-res mice.

    And then when you consider the 2mb/12mb/480mb numbers are the absolute maximum theoretical numbers without overhead, you realize that you get nowhere near this kind of throughput in the first place. Things can get bogged down pretty quickly.

    Personally, I run two separate USB adapters. The built-in USB on the motherboard and a separate PCI USB controller. I leave all the slow things like keyboard and mouse and joysticks on one controller. I put the things that need speed like a dvd burner or mp3 player on the other one and make sure I don't use them at the same time.