TiVo Community Forums Archives - SOAK: USB 1.1 vs 2.0

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SOAK: USB 1.1 vs 2.0
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Posted by: AstroDad

My desktop computer is currently USB 1.1. How can I upgrade to 2.0?

If I buy a 2.0 Hub that is backward compatible, does that mean everything will still be 1.1 if thats what the USB it is connected to is, or will it actually speed it up?

Posted by: Satchel

No hub will speed things up...the USB speed is from your CPU...you'll need a USB 2.0 PCI card to upgrade...

Posted by: Drewster

What Satchel said. But, if any device in a single 'chain' is 1.1, then the chain runs at 1.1.

And remember, powered hubs! Always powered hubs.

Posted by: btwyx

quote:
Originally posted by Drewster
What Satchel said. But, if any device in a single 'chain' is 1.1, then the chain runs at 1.1.

I don't know where that idea came from, but its FALSE, FALSE, FALSE.

If you are downstream of a 1.1 hub then a device can only use 1.1 speeds, that's not surprising, its a 1.1 hub, it doesn't know about high speed. (And, btw, 1.1 Hubs are not allowed under the 2.0 spec.) That's the only thing vaguely similar to your statement that's true. It does not affect any devices above the 1.1 hub in the chain.

If you plug a 1.1 device into a root port (ie directly into the computer), that port becomes the root of a 1.1 bus. It does not affect any other devices plugged into any other ports on the same computer.

If you plug a 1.1 device into a 2.0 hub on a high speed bus, that port, and only that port becomes a 1.1 port. The hub translates between high speed (ie what is usually incorrectly called "2.0" speeds) and full/low speed ("1.1" speeds). This does not affect any other devices attached to this hub. The devices attached to this hub do not suffer any slowdown by virtue of the 1.1 device being plugged in. (Apart from the fact that it gets some of the bandwidth.) In fact the 1.1 devices are slowed down by the high speed devices (that's a rather weird and not well know side effect).

Posted by: LoadStar

The correct terms are:
USB High-Speed - 480 MBits/second
USB Full-Speed - 12 MBits/second
USB Low-Speed - 1.5 MBits/second

USB 1.1 and USB 2.0 are the correct terms for the version of the USB standard being used, but 1.1 and 2.0 have NOTHING to do with the speed. USB 2.0 added the specification for USB High-Speed devices, so the two are often (incorrectly) used interchangably. In fact, I know of several instances of devices that are USB 2.0 compliant, but were USB Full-Speed, NOT USB High-Speed, devices.

However... that said, if the device is only USB 1.1 compliant, then it only will support USB Low-Speed and USB Full-Speed, not USB High-Speed. The device must be USB 2.0 compliant to support all three speeds.

To answer the original question in this thread, there is no way to upgrade a controller from USB 1.1 to USB 2.0. The only thing you can do is purchase a PCI card that contains a USB 2.0 host controller, and plug your devices into those USB ports instead.

Posted by: Drewster

Thanks for the correction btwyx.

quote:
If you plug a 1.1 device into a 2.0 hub on a high speed bus, that port, and only that port becomes a 1.1 port. The hub translates between high speed (ie what is usually incorrectly called "2.0" speeds) and full/low speed ("1.1" speeds).

This is what I was trying to say.

Posted by: AstroDad

thanks for the info guys!

Posted by: btwyx

quote:
Originally posted by LoadStar
However... that said, if the device is only USB 1.1 compliant, then it only will support USB Low-Speed and USB Full-Speed, not USB High-Speed. The device must be USB 2.0 compliant to support all three speeds.

If I were being really picky, you should be saying a 1.1 device will support only "USB Low-Speed or USB Full-Speed", and a 2.0 device can't support all three speeds. A high speed capable device is specifically forbidden from supporting low speed. A 2.0 device may support low speed, or it may support full speed (only), or it may support high and fuill speeds.

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