I'm confused on my USB's


J

jw

I have a machine with a MACHSPEED K8M8MSR2-VC motherboard with four
USB ports on its rear plus two headers with two USB ports each, one of
which isn't connected, the other is. ***The one that is connected is
stated to be USB2 in the MACHSPEED manual. That gives me a total of 6
USB ports.

I have just connected my new IOGEAR GCS1764 4-machine KVM that has
two USB inputs for keyboard and mouse plus two utility USBs for my
printer peripherals plus one USB for each of the computer connections.
The KVM is connected to the USB port flagged above as '***', since I
wanted USB2.

My MACHSPEED keeps giving me a warning that a USB device can run
faster if it were connected to a USB2 port of which it tells me THERE
ARE EIGHT as follows:

VIA USB2.0 ENHANCED CONTROLLER
USB ROOT HUB (8 PORTS)
UNUSED PORT
UNUSED PORT
UNUSED PORT
UNUSED PORT
UNUSED PORT
UNUSED PORT
UNUSED PORT
UNUSED PORT

I don't understand why I am getting the error nor do I understand
where all the USB ports are. Does anyone?

Thanks

Duke
 
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J

jw

My KVM manual says it is USB1.1. I should have thought of that. And
now that I think of it - there ARE eight USB ports total on the KVM.
Dumb me!

Forget I asked.

Duke
 
P

Paul

My KVM manual says it is USB1.1. I should have thought of that. And
now that I think of it - there ARE eight USB ports total on the KVM.
Dumb me!

Forget I asked.

Duke

The latter part might not be true.

You have four USB jacks on the back of the computer. And
you also have two 2x5 USB headers, each of which holds two
ports. That gives a total of 8 USB physical ports.

What you see in Device Manager, is a listing of "logic blocks",
not physical USB ports. A "logic block" controls some number of
ports. The physical ports are not enumerated in Device Manager
(instead, plugged in devices are what is enumerated). I have
a VT8237, and Device Manager shows four VIA "Rev 5" logic blocks,
and an "Enhanced" logic block, for a total of five USB entries
in Device Manager.

VIA Rev 5 or later USB Universal Host Controller \
VIA Rev 5 or later USB Universal Host Controller \__ USB 1.1
VIA Rev 5 or later USB Universal Host Controller /
VIA Rev 5 or later USB Universal Host Controller /
VIA USB Enhanced Host Controller <--- USB 2.0

A USB 1.1 logic block typically controls up to two ports.

A USB 2.0 logic block typically controls six ports. In the case
of your VT8237, it appears they decided to support up to eight
ports with the same logic block.

Sharing a logic block, limits the total bandwidth available on all
the ports. The USB2 logic block runs at up to 60MB/sec. That bandwidth
is shared over up to eight ports. If only one port is busy, it has
access to all the bandwidth. If you were running eight USB webcams,
things might start to bog down because of that sharing. Each port
is not totally independent of the others, and if somehow you could
arrange enough activities on the USB ports, performance would
suffer. Run a bunch of webcams, then try to transfer a file to
your USB hard drive, and the file transfer would be slow.

Now, at the physical port level, when you plug in a USB device, there
is a negotiation that goes on. Initially, the port might run at USB 1.1
rates, and if the driver figures out both ends support USB 2.0, the
physical port can be reconfigured.

And that means, each USB physical port, has a switch on it. The switch
either connects the USB port to a "USB 1.1 logic block" or connects
it to the "USB 2.0 logic block". In the following example, there
are four logic blocks. Three USB 1.1 ones. One USB 2.0 one.
There is enough hardware there, to support six physical ports.
Each physical port has the two position switch, selecting
either USB1.1 or USB2.0 logic for its operation. Your VT8237
would probably have an additional USB 1.1 logic block, plus
have a couple more lines on the USB 2.0 logic block, to support
a total of eight physical ports.

+-----
- - - ----| USB 1.1
| Logic
- - - ----| Block
+-----

+-----
- - - ----| USB 1.1
| Logic
- - - ----| Block
+-----

+-----
- - - ----| USB 1.1
| Logic
x-------------| Block
/ +-----
Physical_port_on_back_of_computer ---x
+-----
x-------------|
|
- - - ----|
|
- - - ----| USB 2.0
| Logic
- - - ----| Block
|
- - - ----|
|
- - - ----|
+-----

If you use a utility like UVCView, the display shown, bears a
resemblance to the picture I just drew. This tool lists the
logic blocks, and whether a physical port has been switched and
connected to it.

http://www.die.de/blog/content/binary/usbview.png

In that example screenshot, there are three USB2 devices,
connected to 1,3,4 spigots on the USB 2.0 logic block. So
three physical ports are likely involved, and all three
ports ended up connected to the USB 2.0 logic block. That
is how I interpret that example screenshot.

If the KVM is limited to USB 1.1, that would account
for operation at 1.1 speeds and the error/warning
dialog box.

Paul
 
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J

jw

The latter part might not be true.

You have four USB jacks on the back of the computer. And
you also have two 2x5 USB headers, each of which holds two
ports. That gives a total of 8 USB physical ports.

What you see in Device Manager, is a listing of "logic blocks",
not physical USB ports. A "logic block" controls some number of
ports. The physical ports are not enumerated in Device Manager
(instead, plugged in devices are what is enumerated). I have
a VT8237, and Device Manager shows four VIA "Rev 5" logic blocks,
and an "Enhanced" logic block, for a total of five USB entries
in Device Manager.

VIA Rev 5 or later USB Universal Host Controller \
VIA Rev 5 or later USB Universal Host Controller \__ USB 1.1
VIA Rev 5 or later USB Universal Host Controller /
VIA Rev 5 or later USB Universal Host Controller /
VIA USB Enhanced Host Controller <--- USB 2.0

A USB 1.1 logic block typically controls up to two ports.

A USB 2.0 logic block typically controls six ports. In the case
of your VT8237, it appears they decided to support up to eight
ports with the same logic block.

Sharing a logic block, limits the total bandwidth available on all
the ports. The USB2 logic block runs at up to 60MB/sec. That bandwidth
is shared over up to eight ports. If only one port is busy, it has
access to all the bandwidth. If you were running eight USB webcams,
things might start to bog down because of that sharing. Each port
is not totally independent of the others, and if somehow you could
arrange enough activities on the USB ports, performance would
suffer. Run a bunch of webcams, then try to transfer a file to
your USB hard drive, and the file transfer would be slow.

Now, at the physical port level, when you plug in a USB device, there
is a negotiation that goes on. Initially, the port might run at USB 1.1
rates, and if the driver figures out both ends support USB 2.0, the
physical port can be reconfigured.

And that means, each USB physical port, has a switch on it. The switch
either connects the USB port to a "USB 1.1 logic block" or connects
it to the "USB 2.0 logic block". In the following example, there
are four logic blocks. Three USB 1.1 ones. One USB 2.0 one.
There is enough hardware there, to support six physical ports.
Each physical port has the two position switch, selecting
either USB1.1 or USB2.0 logic for its operation. Your VT8237
would probably have an additional USB 1.1 logic block, plus
have a couple more lines on the USB 2.0 logic block, to support
a total of eight physical ports.

+-----
- - - ----| USB 1.1
| Logic
- - - ----| Block
+-----

+-----
- - - ----| USB 1.1
| Logic
- - - ----| Block
+-----

+-----
- - - ----| USB 1.1
| Logic
x-------------| Block
/ +-----
Physical_port_on_back_of_computer ---x
+-----
x-------------|
|
- - - ----|
|
- - - ----| USB 2.0
| Logic
- - - ----| Block
|
- - - ----|
|
- - - ----|
+-----

If you use a utility like UVCView, the display shown, bears a
resemblance to the picture I just drew. This tool lists the
logic blocks, and whether a physical port has been switched and
connected to it.

http://www.die.de/blog/content/binary/usbview.png

In that example screenshot, there are three USB2 devices,
connected to 1,3,4 spigots on the USB 2.0 logic block. So
three physical ports are likely involved, and all three
ports ended up connected to the USB 2.0 logic block. That
is how I interpret that example screenshot.

If the KVM is limited to USB 1.1, that would account
for operation at 1.1 speeds and the error/warning
dialog box.

Paul


Thanks


Duke
 

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