From: Chris Holt <amiga2k_at_cox.net>
Date: Fri, 26 Sep 2003 23:21:22 -0400

There are two modes to the USB 1.1 specification. Low and Full speed.
And yes, low speed devices are the only ones where the shielding and
twisted data cabling is recommended, but not required.

Chapter 6.6 of the USB 2.0 specification (and I have no idea why one would
be reading the 1.1 spec, since it's been superseded, in a fully
backward/forward compatible protocol) lists the requirements for High/full
speed cabling as the same. If you check this vs. the 1.1 specification,
there is no difference in the full speed cables and the high/full speed
cables specified in 2.0.

The only devices that operate on low speed are mice, keyboards and other
devices with very low data rate requirements. No MP3 player is going to
transfer files in low speed mode. No one would buy it!

Chris

On Fri, 26 Sep 2003 20:54:44 -0500, Chris Muth wrote:
> There are two versions of USB 1.1, one that runs at 1.5 Mbit, and does
> not require shielding.
> 1.5 Mbit USB is like for keyboards, mice, and such. The other version
> of USB 1.1 is a 12 Mbit version and requires shielding. There might be
> a length restriction on the unshielded version, I didn't read that part
> of the 1.1 spec.
>
> -Chris Muth
>
>
> On 9/26/03 at 6:17 PM Michael O'Quinn wrote:
>
>
>> On Fri, 26 Sep 2003, Chris Holt wrote:
>>
>>
>>> On Fri, 26 Sep 2003 17:24:48 -0700 (PDT), Michael O'Quinn wrote:
>>>
>>>> It may not be USB 2.0 certified, and if not it may or may not
>>>> work at the higher speed.
>>>>
>>>
>>> There is no USB 2.0 certification for cables. The spec did not
>>> change from the 1.1 specification. That is not to say that many
>>> cable manufacturers did not take advantage of the lesser
>>> requirements of USB
>>>
>> 1.1
>>> and make substandard cables, but simply that the specification for
>>> USB cables has always been the same.
>>>
>>
>> As I understand it, the 2.0 spec requires cables to be shielded,
>> whereas 1.x did not.
>>
>> Of course, that may all be hogwash.
>>
>>
>> Then again, I've noticed that all motherboards I've seen with USB 2.0
>> headers have an extra pin for the cable shield, and that was never
>> (or very rarely) there with USB 1.x.
>>
>> Michael
Received on 2003-09-27