USB distance limits?

2 Apr 2005 7:29 AM

Norm

Has anybody any experience with longer USB cables?
I know there is some theoretical limit like 6 or 10 feet, but I also know
with RS232 there used to be a limit of 50 feet. I know I was able to quite
reliably run over 200 feet, so I am wondering how far USB can actually go.

2 Apr 2005 8:23 AM

philo

"Norm" <normgrant***@yahoo.ca> wrote in message

news:bRr3e.872473$Xk.206063@pd7tw3no...

> Has anybody any experience with longer USB cables?
> I know there is some theoretical limit like 6 or 10 feet, but I also know
> with RS232 there used to be a limit of 50 feet. I know I was able to quite
> reliably run over 200 feet, so I am wondering how far USB can actually go.
>
>

it depends on the speed of the device and
the current draw.
although i do recall reading that there is a 6 foot limit...
i know as a fact that i;ve seen 20 foot cables being sold in computer
stores...

have a look on google you should get a lot of results

2 Apr 2005 10:33 AM

Veritech

the 20 foot thing is normally some manufacturer trying dupe people.

its like ide cables, the offical spec says that should be no longer than
24cm ( i think), after that data corruption becomes an issue, yet tons of
makers have 48cm cables. So really you should avoid them, but when needs
must, i guess you got no choice.
Show quoteHide quote

"philo" <ph***@privacy.net> wrote in message
news:4N2dnZ78udP5y9PfRVn-3g@athenet.net...
>
> "Norm" <normgrant***@yahoo.ca> wrote in message
> news:bRr3e.872473$Xk.206063@pd7tw3no...
>> Has anybody any experience with longer USB cables?
>> I know there is some theoretical limit like 6 or 10 feet, but I also know
>> with RS232 there used to be a limit of 50 feet. I know I was able to
>> quite
>> reliably run over 200 feet, so I am wondering how far USB can actually
>> go.
>>
>>
>
> it depends on the speed of the device and
> the current draw.
> although i do recall reading that there is a 6 foot limit...
> i know as a fact that i;ve seen 20 foot cables being sold in computer
> stores...
>
>
> have a look on google you should get a lot of results
>
>

2 Apr 2005 11:33 AM

Crazy John

> the 20 foot thing is normally some manufacturer trying dupe people.
>
> its like ide cables, the offical spec says that should be no longer than
> 24cm ( i think), after that data corruption becomes an issue, yet tons of
> makers have 48cm cables. So really you should avoid them, but when needs
> must, i guess you got no choice.

i'd say it's bullsh*t i've got 90cm ide cable and everything is ok... it
depends on the particular pc i guess...

2 Apr 2005 12:21 PM

JANA

It really depends on the device at the end of the cable, and how much
current the device is pulling from the port. I've used 10 feet, and it
worked. I have had other devices that after 6 feet, they start to give
problems. For example, I would not exceed 4 or 5 feet for a USB hard drive,
or a DVD burner. But, for a simple mouse, this may work up to 10 feet.

--

JANA
_____

"Norm" <normgrant***@yahoo.ca> wrote in message

news:bRr3e.872473$Xk.206063@pd7tw3no...
Has anybody any experience with longer USB cables?
I know there is some theoretical limit like 6 or 10 feet, but I also know
with RS232 there used to be a limit of 50 feet. I know I was able to quite
reliably run over 200 feet, so I am wondering how far USB can actually go.

2 Apr 2005 3:46 PM

Alceryes

"Norm" <normgrant***@yahoo.ca> wrote in message

news:bRr3e.872473$Xk.206063@pd7tw3no...

> Has anybody any experience with longer USB cables?
> I know there is some theoretical limit like 6 or 10 feet, but I also know
> with RS232 there used to be a limit of 50 feet. I know I was able to quite
> reliably run over 200 feet, so I am wondering how far USB can actually go.
>

USB 2.0 specs say no longer than 4 meters.
http://www.usb.org/home
With that said it also depends on the quality of the cable and how thick
it's shielding is. The better the cable the farther it will work 'out of
spec'.

--

"I don't cheat to survive. I cheat to LIVE!!"
- Alceryes

2 Apr 2005 5:15 PM

William W. Plummer

Alceryes wrote:

Show quoteHide quote

> "Norm" <normgrant***@yahoo.ca> wrote in message
> news:bRr3e.872473$Xk.206063@pd7tw3no...
>
>>Has anybody any experience with longer USB cables?
>>I know there is some theoretical limit like 6 or 10 feet, but I also know
>>with RS232 there used to be a limit of 50 feet. I know I was able to quite
>>reliably run over 200 feet, so I am wondering how far USB can actually go.
>>
>
>
> USB 2.0 specs say no longer than 4 meters.
> http://www.usb.org/home
> With that said it also depends on the quality of the cable and how thick
> it's shielding is. The better the cable the farther it will work 'out of
> spec'.

I believe the issue is delay time. The bit rate is 480 MHz or close to
2 ns per bit. A 4 meter cable has a delay of about 15 ns. So any
back-and-forth signaling must not add many round trip delays in order to
get the data flowing. Cable quality is important but will not change
the speed of light.