A limit on number of USB hubs in Windows 7?


Y

Yousuf Khan

I've got three 4-port hubs on my system. From time to time after a
reboot, some of them don't enumerate properly, and you have to unplug
and replug them. Is there some way in software to get Windows to rescan
them? Of course that won't do any good if the USB hub that your mouse
and keyboard are on is the one that doesn't get enumerated properly, but
I'm tired of reaching into the back to unplug them.

Also is there a known limit on how many USB devices that can be put into
a single machine? I have at least over a dozen USB devices connected at
a time usually, sometimes more.

Yousuf Khan
 
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G

Gene E. Bloch

I've got three 4-port hubs on my system. From time to time after a
reboot, some of them don't enumerate properly, and you have to unplug
and replug them. Is there some way in software to get Windows to rescan
them? Of course that won't do any good if the USB hub that your mouse
and keyboard are on is the one that doesn't get enumerated properly, but
I'm tired of reaching into the back to unplug them.

Also is there a known limit on how many USB devices that can be put into
a single machine? I have at least over a dozen USB devices connected at
a time usually, sometimes more.

Yousuf Khan
There's a limit, but it's pretty big, like 256 total devices, IIRC.

Hubs shouldn't matter. Four ports on a hub shouldn't be different from 4
ports without a hub, again pleading IIRC...

But for some reason USB hubs don't always play well with every device or
every computer. Maybe your variable performance depends on the whole
constellation of what is plugged into each hub on a particular Tuesday?

I can't get into Safe Mode on this computer if I have my mouse and keyboard
plugged into a hub, even with one keyboard I have where the mouse port is
on the keyboard...
 
A

Al Dykes

I've got three 4-port hubs on my system. From time to time after a
reboot, some of them don't enumerate properly, and you have to unplug
and replug them. Is there some way in software to get Windows to rescan
them? Of course that won't do any good if the USB hub that your mouse
and keyboard are on is the one that doesn't get enumerated properly, but
I'm tired of reaching into the back to unplug them.

Also is there a known limit on how many USB devices that can be put into
a single machine? I have at least over a dozen USB devices connected at
a time usually, sometimes more.

Yousuf Khan
Are they all powered hubs?
 
R

R. C. White

Hi, Yousuf.

Like Gene, I can't recall for sure but I think the limit is 127 USB devices.

And like Al, I wonder about power to - and through - the hubs.

My own experience was with my wireless desktop (keyboard and mouse). They
use the 2.4 GHz transceiver, which plugs into a USB port. When I plugged it
into my only 4-port hub, the keyboard worked fine - until time to reboot,
when there was no communication with the keyboard during startup, making it
impossible to choose the Windows version to dual-boot. So I moved the
transceiver to the back of the computer, plugging it into a USB port
directly on the motherboard. Then I could dual-boot just fine - but the
keyboard often went to sleep right in the middle of typing a message like
this post. It would seem dead for about 2 minutes, then resume normal
performance. After trying many other fixes, I finally realized that the
hub's connection was to an add-on USB on a PCI card. So I moved the hub's
USB to that mainboard USB port and put the keyboard transceiver into the hub
again. Problem solved! ;<)

While I haven't tried to do the arithmetic for the amount of power and how
it gets divided, I suspect that the hub was not getting enough power from
the add-on card to satisfy the keyboard. Or the hub couldn't handle the
connection until Windows started and loaded its driver. In other words, the
number of USB devices was not a problem (there are no more than a half-dozen
total on my system), but the connection pathway from the mainboard to the
device created a partial roadblock. The more-direct connection provides
more power, and it probably also simplifies the data pathway.

So, how and where are each of your hubs plugged in to your computer?

RC
--
R. C. White, CPA
San Marcos, TX
(e-mail address removed)
Microsoft Windows MVP
Windows Live Mail 2010 (15.3.2804.0607) in Win7 Ultimate x64

"Yousuf Khan" wrote in message
I've got three 4-port hubs on my system. From time to time after a
reboot, some of them don't enumerate properly, and you have to unplug
and replug them. Is there some way in software to get Windows to rescan
them? Of course that won't do any good if the USB hub that your mouse
and keyboard are on is the one that doesn't get enumerated properly, but
I'm tired of reaching into the back to unplug them.

Also is there a known limit on how many USB devices that can be put into
a single machine? I have at least over a dozen USB devices connected at
a time usually, sometimes more.

Yousuf Khan
 
A

Andrew

Yousuf Khan said:
I've got three 4-port hubs on my system. From time to time after a reboot,
some of them don't enumerate properly, and you have to unplug and replug
them. Is there some way in software to get Windows to rescan them? Of
course that won't do any good if the USB hub that your mouse and keyboard
are on is the one that doesn't get enumerated properly, but I'm tired of
reaching into the back to unplug them.

Also is there a known limit on how many USB devices that can be put into a
single machine? I have at least over a dozen USB devices connected at a
time usually, sometimes more.

Yousuf Khan
Go to Device Manager and right click on the root.
Select "Scan for hardware changes"
 
Y

Yousuf Khan

There's a limit, but it's pretty big, like 256 total devices, IIRC.
Yeah, but that would be the official specification limit. I'm thinking
more along the lines of the unofficial "real" limits.

It also seems to be operating system dependent. Sometimes Windows XP or
Linux seem to have less trouble seeing these hubs, sometimes not. This
is all on the same machine, of course.
Hubs shouldn't matter. Four ports on a hub shouldn't be different from 4
ports without a hub, again pleading IIRC...
I even had a 7 port hub once, but that was a nightmare, it had the worst
problems of them all being enumerated. The 7 port hubs are also
internally daisy-chained, where one 4 port hub plugs into another 4 port
hub, so I assumed it was due to this.
But for some reason USB hubs don't always play well with every device or
every computer. Maybe your variable performance depends on the whole
constellation of what is plugged into each hub on a particular Tuesday?
That's basically the best way to describe it. :)
I can't get into Safe Mode on this computer if I have my mouse and keyboard
plugged into a hub, even with one keyboard I have where the mouse port is
on the keyboard...
I also seem to have trouble getting some of my hubs to show up as USB
2.0 hubs, meaning working at 480-Mbps. They are all listed as USB 2.0
hubs but usually two of them seem to fall back down to the USB 1.1
15-Mbps speed. One will always show up at the full 480-Mbps speed, but
the other two will go back to lower speeds.

Yousuf Khan
 
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Y

Yousuf Khan

Are they all powered hubs?
No, one of them was, and that was the one with the biggest problems. The
problems got slightly better when I removed the power cord from it.

When it was self-powered, eventually it started crashing the machine.
Not right away, but the problems got worse and worse until the machine
got unstable and crashed. When I removed the power cord from it, it
would just sometimes fail to enumerate, but it wouldn't crash the machine.

Yousuf Khan
 
Y

Yousuf Khan

So, how and where are each of your hubs plugged in to your computer?
All of the USB hubs are connected directly through the motherboard's own
USB ports, no separate add-in USB card involved here.

Yousuf Khan
 
Y

Yousuf Khan

Go to Device Manager and right click on the root.
Select "Scan for hardware changes"
Actually I've tried that before, and it only rediscovers anything after
I unplug and replug.

Yousuf Khan
 
D

Dave \Crash\ Dummy

Yousuf said:
I've got three 4-port hubs on my system. From time to time after a
reboot, some of them don't enumerate properly, and you have to unplug
and replug them. Is there some way in software to get Windows to
rescan them? Of course that won't do any good if the USB hub that
your mouse and keyboard are on is the one that doesn't get enumerated
properly, but I'm tired of reaching into the back to unplug them.

Also is there a known limit on how many USB devices that can be put
into a single machine? I have at least over a dozen USB devices
connected at a time usually, sometimes more.

Yousuf Khan
I don't know squat about USB, but you might avoid the mouse/keyboard
uncertainty by using the PS/2 connectors (if available) for them, instead.
 
G

Grandfather of TOS

get better quality hubs, make sure all of them are the same brand.

"Yousuf Khan" wrote in message
I've got three 4-port hubs on my system. From time to time after a
reboot, some of them don't enumerate properly, and you have to unplug
and replug them. Is there some way in software to get Windows to rescan
them? Of course that won't do any good if the USB hub that your mouse
and keyboard are on is the one that doesn't get enumerated properly, but
I'm tired of reaching into the back to unplug them.

Also is there a known limit on how many USB devices that can be put into
a single machine? I have at least over a dozen USB devices connected at
a time usually, sometimes more.

Yousuf Khan
 
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S

Shoe

I don't know squat about USB, but you might avoid the mouse/keyboard
uncertainty by using the PS/2 connectors (if available) for them, instead.
I've been having a problem with my wireless keyboard and mouse for a
long time. They don't work at boot until the OS starts and they will
not wake the computer from sleep (Windows 7). Another response in
this thread said that they should be connected directly to a port on
the motherboard. Mine was connected to a slot on an expansion card. I
moved the plug to the motherboard and it fixed the problem. It
appears as if the computer sees hub connections and expansion card
connection differently than motherboard connections. Problem solved
for me - thanks to the person who posted that solution. By the way, I
talked to Intel online chat and they said the problem was that my
motherboard is not fully compatible with Windows 7, even though there
is no problem when the OS is running.
 
A

Antares 531

I've got three 4-port hubs on my system. From time to time after a
reboot, some of them don't enumerate properly, and you have to unplug
and replug them. Is there some way in software to get Windows to rescan
them? Of course that won't do any good if the USB hub that your mouse
and keyboard are on is the one that doesn't get enumerated properly, but
I'm tired of reaching into the back to unplug them.

Also is there a known limit on how many USB devices that can be put into
a single machine? I have at least over a dozen USB devices connected at
a time usually, sometimes more.

Yousuf Khan
I don't have anything in the way of an answer, but I have a similar
problem with my computer, running Windows 7 with all the updates. This
is a home-built computer with an AZUS P7P55D motherboard. I have a
DYNEX hub plugged into the motherboard's USB connection on the back of
the computer, then have my keyboard and mouse plugged into this DYNEX
hub. It will lock up, or freeze, from time to time, and I have to
un-plug if from the motherboard connection, then plug it back in to
get the keyboard and mouse back to normal. This will occur in a random
way, and I have not figured out anything that could be causing it.
Just un-plugging the DYNEX hub for a moment then plugging it back in
seems to get things resolved, and it may work well for several days,
or it may go kaput again within a few minutes or hours.

Gordon
 
R

R. C. White

Hi, Gordon (and Shoe).

Hubs need drivers. These don't get loaded until after Windows starts - so
they can be used during the start-up process BEFORE Windows gets loaded.

Mainboard ports generally are supported by the BIOS. So settings in CMOS -
not in Windows - can make them become active very early in the boot process,
long before the dual-boot menu appears on the screen. Some older mainboards
don't support this, but all newer ones should.

Your keyboard "lock up, or freeze" sounds just like mine, as described in my
earlier post in this thread. I fixed this by moving the USB transceiver to
a mainboard port - but then, as Shoe said, I couldn't switch OSes at boot
time. When I finally moved the hub's USB plug to the mobo port, it solved
both problems. The blue light on the hub port that holds the transceiver
lights up early in the boot process. And the hub is about 2 feet closer to
the keyboard than the mainboard port on the back of the computer case, so
the keyboard gets a better and more consistent signal from the transceiver.

My 4-year-old mobo has lots of USB ports. Four are direct connections on
the backplane. The mobo also has 3 sets of pins supporting 2 external ports
each; I've connected 2 of these to USB brackets on the back and one to the
front of the computer case, giving me 6 more ports. These are all USB 2.0.
Plus a PCI card (USB 1.0) left over from my former system, which I plugged
in "just because", giving me a total of 12 USB ports. The 4-port hub uses
one of the backplane ports, upping the count to 15. ;^} The main benefit
of the hub - besides being closer to the keyboard - is that I can plug in my
SD card reader without fumbling blindly on the back of the computer case.

RC
--
R. C. White, CPA
San Marcos, TX
(e-mail address removed)
Microsoft Windows MVP
Windows Live Mail 2010 (15.3.2804.0607) in Win7 Ultimate x64


"Antares 531" wrote in message

I've got three 4-port hubs on my system. From time to time after a
reboot, some of them don't enumerate properly, and you have to unplug
and replug them. Is there some way in software to get Windows to rescan
them? Of course that won't do any good if the USB hub that your mouse
and keyboard are on is the one that doesn't get enumerated properly, but
I'm tired of reaching into the back to unplug them.

Also is there a known limit on how many USB devices that can be put into
a single machine? I have at least over a dozen USB devices connected at
a time usually, sometimes more.

Yousuf Khan
I don't have anything in the way of an answer, but I have a similar
problem with my computer, running Windows 7 with all the updates. This
is a home-built computer with an AZUS P7P55D motherboard. I have a
DYNEX hub plugged into the motherboard's USB connection on the back of
the computer, then have my keyboard and mouse plugged into this DYNEX
hub. It will lock up, or freeze, from time to time, and I have to
un-plug if from the motherboard connection, then plug it back in to
get the keyboard and mouse back to normal. This will occur in a random
way, and I have not figured out anything that could be causing it.
Just un-plugging the DYNEX hub for a moment then plugging it back in
seems to get things resolved, and it may work well for several days,
or it may go kaput again within a few minutes or hours.

Gordon
 
A

Antares 531

Thanks, R.C. This does explain some things, but I'm still not sure
what causes my computer's mouse and keyboard to lock up. This usually
happens long after booting up or coming out of hibernation. It occurs
while I'm working, and for no specific reason that I've been able to
figure out. That is, it happens without any unusual computer commands
or activity. I can be typing or viewing some message like this one and
the lock-up will occur. I pull the USB cable out of the socket and get
the normal ding-dong that indicates some hardware change has been
made. Then when I plug the USB cable back in I hear the ding-dong
again and the mouse/keyboard are again functioning normally.

I'm reasonably convinced that my problem is caused by the DYNEX hub.
It may be on the verge of failure, for some reason. That is, I can
plug the keyboard and mouse into the computer's other USB ports,
without the DYNEX hub and this problem doesn't occur...at least I've
never had it happen. But, plugging the mouse and keyboard in,
directly, without the DYNEX hub means laying the USB cords across my
desktop, and that is a bit messy. I use the DYNEX hub to effectively
lengthen the keyboard and mouse USB cords so I can route them beneath
my desktop. I have a little pull-out shelf just above my knees that
holds the mouse and keyboard, but the distance from there to the back
of the computer is too great to plug them in without bringing the
cords up and over the desktop.

This DYNEX hub has a provision for a power input, but I am not using
this, since my mouse and keyboard do not need it.
 
R

Rodney Pont

I use the DYNEX hub to effectively
lengthen the keyboard and mouse USB cords so I can route them beneath
my desktop. I have a little pull-out shelf just above my knees that
holds the mouse and keyboard, but the distance from there to the back
of the computer is too great to plug them in without bringing the
cords up and over the desktop.
You can get USB male 'A' to Female 'A' extension cables in various
lengths and can get to 5m before you need an active cable with a
repeater in, see:

http://www.cclonline.com/product-categories.asp?category_id=178
 
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R

R. C. White

Hi, Gordon.

Well, I made an obvious typo in the first sentence of my last post. It
should say:
Hubs need drivers. These don't get loaded until after Windows starts - so
they can NOT be used during the start-up process BEFORE Windows gets
loaded.
Have you tried plugging your DYNEX hub's INPUT cable into one of the other
ports? Find a port that makes your keyboard work properly without the hub.
Then move the keyboard's USB connector from there to the DYNEX hub - and
move the hub's connector to where you just unplugged the keyboard.

That was all it took for my unpowered cheapie $10 Targus hub from Wal*Mart
to work for my rig. My hub plugs into one of the 4 mainboard ports, then
its 6' cord lets its 4 connectors lie on top of my computer case, just about
3 feet from my keyboard. My theory is that this eliminates any kind of
driver for the hub itself (except what is built into Win7), letting signals
(and power) travel straight through from the mobo/BIOS/USB/hub/USB
transceiver - then wirelessly to the keyboard.

RC
--
R. C. White, CPA
San Marcos, TX
(e-mail address removed)
Microsoft Windows MVP
Windows Live Mail 2010 (15.3.2804.0607) in Win7 Ultimate x64

"Antares 531" wrote in message

Thanks, R.C. This does explain some things, but I'm still not sure
what causes my computer's mouse and keyboard to lock up. This usually
happens long after booting up or coming out of hibernation. It occurs
while I'm working, and for no specific reason that I've been able to
figure out. That is, it happens without any unusual computer commands
or activity. I can be typing or viewing some message like this one and
the lock-up will occur. I pull the USB cable out of the socket and get
the normal ding-dong that indicates some hardware change has been
made. Then when I plug the USB cable back in I hear the ding-dong
again and the mouse/keyboard are again functioning normally.

I'm reasonably convinced that my problem is caused by the DYNEX hub.
It may be on the verge of failure, for some reason. That is, I can
plug the keyboard and mouse into the computer's other USB ports,
without the DYNEX hub and this problem doesn't occur...at least I've
never had it happen. But, plugging the mouse and keyboard in,
directly, without the DYNEX hub means laying the USB cords across my
desktop, and that is a bit messy. I use the DYNEX hub to effectively
lengthen the keyboard and mouse USB cords so I can route them beneath
my desktop. I have a little pull-out shelf just above my knees that
holds the mouse and keyboard, but the distance from there to the back
of the computer is too great to plug them in without bringing the
cords up and over the desktop.

This DYNEX hub has a provision for a power input, but I am not using
this, since my mouse and keyboard do not need it.
 
A

Antares 531

You can get USB male 'A' to Female 'A' extension cables in various
lengths and can get to 5m before you need an active cable with a
repeater in, see:

http://www.cclonline.com/product-categories.asp?category_id=178
I guess I should try this...extension cables...I was just trying to
minimize the clutter of cables and hardware on my desktop when I went
for the DYNEX hub and put it under the desktop, with only one cable
instead of two, hooked to the back of my computer.
 
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A

Antares 531

Hi, Gordon.

Well, I made an obvious typo in the first sentence of my last post. It
should say:

Have you tried plugging your DYNEX hub's INPUT cable into one of the other
ports? Find a port that makes your keyboard work properly without the hub.
Then move the keyboard's USB connector from there to the DYNEX hub - and
move the hub's connector to where you just unplugged the keyboard.

That was all it took for my unpowered cheapie $10 Targus hub from Wal*Mart
to work for my rig. My hub plugs into one of the 4 mainboard ports, then
its 6' cord lets its 4 connectors lie on top of my computer case, just about
3 feet from my keyboard. My theory is that this eliminates any kind of
driver for the hub itself (except what is built into Win7), letting signals
(and power) travel straight through from the mobo/BIOS/USB/hub/USB
transceiver - then wirelessly to the keyboard.

RC
I tried plugging the DYNEX hub into some of the ports other than the
one that is located by the motherboard's conventional round sockets
(can't remember what they're called) but the result was the same. I
don't have these lock-up problems very frequently...two or three times
a week, usually.

The only setup that seemed to get around these lock-up problems was to
plug the keyboard and mouse into the computer's USB sockets on the
front panel of the computer...with no USB hub.
 

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