question on USB 1.1 and 2.0 together

  • Thread starter Thread starter James
  • Start date Start date
J

James

I'm definitely not up to date with the world of hardware these days. The
shortest way for me to ask this is to simply write my assumption, then
question. Please let me know if my assumption is wrong.

assumption: when a 1.1 and 2.0 devices are plugged into the same usb 2.0 bus
both devices have to operate at usb 1.1 speeds.

1) does this mean even having a usb 1.1 keyboard and a fast usb 2.0
harddrive on the same 2.0 bus will kill the harddrive performance?

2) most pc's have many usb ports... are they all typically on one usb bus,
or are there multiple buses? If multiple buses then I assume you could group
1.1 devices on one bus and only 2.0 devices on another bus to avoid bringing
the 2.0 devices down?

a mix of assumptions and questions there... if someone could set me straight
on this I would really appreciate it.

thanks.
 
I'm definitely not up to date with the world of hardware these days. The
shortest way for me to ask this is to simply write my assumption, then
question. Please let me know if my assumption is wrong.

assumption: when a 1.1 and 2.0 devices are plugged into the same usb 2.0 bus
both devices have to operate at usb 1.1 speeds.

1) does this mean even having a usb 1.1 keyboard and a fast usb 2.0
harddrive on the same 2.0 bus will kill the harddrive performance?

2) most pc's have many usb ports... are they all typically on one usb bus,
or are there multiple buses? If multiple buses then I assume you could group
1.1 devices on one bus and only 2.0 devices on another bus to avoid bringing
the 2.0 devices down?

a mix of assumptions and questions there... if someone could set me straight
on this I would really appreciate it.

thanks.
Click to expand...

Not sure about combining USB 1.1 and USB 2 devices on the same bus but
I know for certain that if the on-board USB ports can do both USB 2
and USB 1.1. Each port are paired to one USB root hub and depending
on the motherboard, the root hubs are independent from each other.
 
thanks for the input.

I'm definitely not up to date with the world of hardware these days. The
shortest way for me to ask this is to simply write my assumption, then
question. Please let me know if my assumption is wrong.

assumption: when a 1.1 and 2.0 devices are plugged into the same usb 2.0
bus
both devices have to operate at usb 1.1 speeds.

1) does this mean even having a usb 1.1 keyboard and a fast usb 2.0
harddrive on the same 2.0 bus will kill the harddrive performance?

2) most pc's have many usb ports... are they all typically on one usb bus,
or are there multiple buses? If multiple buses then I assume you could
group
1.1 devices on one bus and only 2.0 devices on another bus to avoid
bringing
the 2.0 devices down?

a mix of assumptions and questions there... if someone could set me
straight
on this I would really appreciate it.

thanks.
Click to expand...

Not sure about combining USB 1.1 and USB 2 devices on the same bus but
I know for certain that if the on-board USB ports can do both USB 2
and USB 1.1. Each port are paired to one USB root hub and depending
on the motherboard, the root hubs are independent from each other.
 
Keep in mind that *all* of today's devices and ports are USB 2.0. What we
really mean is Low speed, full speed, and Hi-Speed. Even Intel is attempting
to change its language this way, but the message isn't making it to their
tech support people.

A low-speed keyboard and hi-speed flash on the same port MAY slow that port
to low-speed. The port will detect what's out there, and switch between the
hi-speed controller and the low/full speed controller. As to what actually
happens, it seems easy to test, right? For a real test get a copy of
UVCView.exe (A MS tool that's available all over the place) to expose what
each port is up to. I have another program here called bench32 that measures
USB performance.

Paul helped me with this a few months ago:
http://www.intel.com/design/chipsets/datashts/313056.htm
Go to page 218. Might not be your chipset, but the description may be
enlightening. Here's the original thread: http://tinyurl.com/6ntax7

-John O
 
James said:
I'm definitely not up to date with the world of hardware these days. The
shortest way for me to ask this is to simply write my assumption, then
question. Please let me know if my assumption is wrong.

assumption: when a 1.1 and 2.0 devices are plugged into the same usb 2.0
bus both devices have to operate at usb 1.1 speeds.

1) does this mean even having a usb 1.1 keyboard and a fast usb 2.0
harddrive on the same 2.0 bus will kill the harddrive performance?

2) most pc's have many usb ports... are they all typically on one usb bus,
or are there multiple buses? If multiple buses then I assume you could
group 1.1 devices on one bus and only 2.0 devices on another bus to avoid
bringing the 2.0 devices down?

a mix of assumptions and questions there... if someone could set me
straight on this I would really appreciate it.
Click to expand...

The USB1 and USB2 hardware on your motherboard are physically different
systems. Whichever type of devices that you plug in, they are all
automagically routed to the correct hardware ports which transparently
achieves your point 2. The practical upshot is: that you can freely mix
USB2 and USB1 devices on your motherboard ports without worrying if one is
going to affect another. This is also true of USB2 hubs.
 
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