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View Full Version : USB2 compatible with USB1 ?



Zaccheus
20th Nov 2002, 14:42
No, of course not.

BUT, I wish to buy one of these (http://www.ebuyer.com/customer/products/index.html?action=c2hvd3N1YmNhdGVnb3J5X3BhZ2U=&subcat_uid=123) external CD-RW's, but they are all USB2.

Now, generally speaking, will these ALSO work with USB1 ports, or do I need USB2?

Vanguard
20th Nov 2002, 17:16
The typical USB ports on the back of the system case (i.e., off the motherboard) are low powered USB1. That is, they only support the slower USB1 spec and they only work for low-powered devices. If you have a high-power device then you need to get a powered USB port hub; the low-power USB1 ports on your mobo get connected to the high-power USB hub, and the high-power device connects to the powered USB hub. I think you can connect maybe 1 high-powered USB device to the mobo USB ports but it depends on how much current the device needs. You can't use the other mobo USB port; it's current is getting sucked up by the high-powered device on the other USB port (i.e., they share the current draw). If the USB device supplies its own power (instead of robbing it from the USB ports) then you don't need a powered USB hub for the high-powered USB device.

USB 2.0 is much faster than USB 1.0. I think USB 1.0 was a 12 Mbit/sec interface. USB 2.0 covers 1.5 Mbps, 12 Mbps, and 480 Mbps (40 times faster than USB 1.0). I don't know if USB2 is a high-powered port; it still might be a low-powered spec in which case you will still need a powered USB2 hub. If the device worked on a USB1 port, it should work on a USB2 port - but not the other way around. However, apparently there were 2 interface specs for USB 1.0 so it is possible that a device for USB 1.0 might not work on USB 2.0; see the link below.

First there was USB 1.0. Then USB 2.0. Now there's USB 2.0 Enhanced (http://www.usb.org/data/press/press20/2002_04_17_intel.pdf). A FAQ is available at http://www.usb.org/faq.html; however, it isn't clear in differentiating USB 1.0 from 2.0. More info is available at http://www.microsoft.com/hwdev/bus/USB/default.asp, http://www.intel.com/technology/usb/index.htm and http://www.usb.org/developers/docs.html.

With the external CD-RW drives, they probably provide their own power via a transformer at the end of the power cord. So you don't need a powered USB hub. They are rated USB 2.0 but should work albeit slower on a USB 1.0 port. Check with the device manufacturer first regarding compliance of their USB 2.0 devices when connected to USB 1.0 ports. Your motherboard, if new enough, may provide USB 2.0 ports. However, many that I've seen still only provide USB 1.0 on the mobo embedded ports that come out the back and you have to connect a card blank with USB ports to headers on the mobo for the USB 2.0 ports. If you mobo doesn't provide USB 2.0 ports, you could insert a USB 2.0 card into a PCI slot.

Zaccheus
21st Nov 2002, 09:19
Thanks.
:)