Paul
Fri May 30 11:05:38 PDT 2008
JohnO wrote:
> "Paul" <nospam@needed.com> wrote in message news:g1pbcp$a8n$1@aioe.org...
>> JohnO wrote:
>>> I'm playing with two things, an Intel DG965SS mobo and Microsoft's
>>> UVCView.exe USB tool. UVCView shows that there are seven root hubs, two
>>> of which contain the magic word: Enhanced, which means they are Hi-Speed
>>> USB. The board has ten physical ports.
>>>
>>> When I inventory the physical ports....plug in a device and see which
>>> root hub/port is connected to each physical port, none of the physical
>>> ports match up to the two Enhanced Root hubs shown in UVCView.
>>>
>>> At first glance that would mean I don't have any hi-speed USB ports,
>>> right? But, the Intel product specs claim hi-speed on all ten physical
>>> ports.
>>>
>>> So, is it possible that UVCView isn't showing me the entire story, and
>>> that the mere presence of an Enhanced root hub (anywhere) means I've got
>>> hi-speed everywhere?
>>>
>>> Do some motherboards have mixed USB...some full-speed and some hi-speed?
>>> If so, how do I determine which is which?
>>>
>>> -John O
>>>
>> Using ICH8 datasheet from Intel - Table 13 mentions physical port mapping
>> to
>> controller. Table title is "USB Interface Signals".
>>
>>
http://www.intel.com/design/chipsets/datashts/313056.htm
>>
>> Six USB ports are on one controller, four USB ports on the other.
>> There should be two enhanced entries in UVCView. One should have
>> room for six entries, the other with four entries.
>
> Yep, that's it. and ten other ports, too.
>
>> You should see two Enhanced entries in Device Manager. That
>> would tell you there is a USB2 driver in place.
>
> Yes.
>
>> Then, when you use a test device, which is USB2 capable, and
>> test each USB jack, it should show in the area in
>> UVCView, where there are the six entry and four entry sections.
>> (At least, if UVCView can handle all those entries.)
>
> Aha...if I connect a hi-speed device it *does* show up on one of the
> Enhanced hub/ports. But if I use a slow device, it shows up on a different
> hub altogether. That explains it: There are 20 ports listed, 10 for slow and
> 10 for hi-speed...I get a port based on the device.
>
> I had been using a slow flash drive and a cheap hub, assuming that the
> physical ports were tied to logical ports, but now I see that's not the
> case.
>
> But, just switching to a 2.0/hi-speed hub makes all the difference. This
> gives me a lot to think about and a lot to work with.
>
>
>> The era of "mixed" USB is long past. There was a time, when
>> USB2 just started appearing, where some chipsets only had USB1.1,
>> and a separate NEC chip or similar may have been bolted to the
>> motherboard, to give some USB2 ports. The stacks on the back
>> of the computer, may have mixed the two types together (but the
>> motherboard manual identified which was which).
>>
>> With modern motherboards, that is no longer necessary.
>
> OK, that's good.
>
> Thanks Paul, I appreciate the help on this.
>
> -John O
>
PDF page 218 of the Intel ICH8 document, has a picture of the USB details.
(See "ICH8-USB Port Connections".) There are a total of seven logic blocks.
Two USB2 and five USB1.1 . Each USB1.1 controller, handles a stack of two
ports. The USB2 ones are six ports and four ports respectively.
When you plug in a USB device to one of the ten physical ports,
during the setup, there is a binding between the physical port,
and one of the seven logic blocks. (That is what those little "switches"
in the diagram are meant to represent.) And that is why, a newly plugged
device, will either show up under a "group of two" USB1.1 block,
or a larger grouping used on the USB2 blocks. And that is also why
UVCView shows twenty entries, when the chip has ten ports.
The purpose of putting two USB2 blocks, in this chip, is to increase
the maximum simultaneous bandwidth on USB. A total of 120MB/sec max,
60MB/sec per USB2 controller, is shared over the ten ports. If you
had a couple high resolution web cams, or some other demanding
application, where normally you'd run out of bandwidth, and the
hardware devices would be unhappy (jerky etc), if you plug one
into each USB2 controller logic block, then things could improve.
My ICH5 has eight ports, on one USB2 block. So 60MB/sec is shared
8 ways on my older motherboard. Protocol overhead limits available
bandwidth, and 57MB/sec is a theoretical max, while with a USB2
external hard drive, I might see around 33-35MB/sec on a good day.
Paul
