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Does Cable Quality Matter?

"Get quality cables!"  "Poor cables mean poor speed and performance!"  "Upgrade you cables for better performance!"

These are something that you hear time and time again (I think I might have been responsible for saying them a few time myself).  There's this idea running through the PC world like a golden thread that quality equates to speed.  It's not only in the PC universe either, walk into any store selling audio and video gear and you will see grey plastic "budget" cables next to hi-tech, metallic, futuristic looking cables that sell for upwards of twenty times the price.

But do cables matter?  Well, I decided to find out by looking at a single USB 2.0 device and seeing whether the performance was better or worse when the device was hooked to the PC USB port direct or with a low-quality, low-cost, no-name cable in-between the device and the port.  I was planning on trying this experiment using a cable branded as "high quality" but I didn't have a USB A to A cable like that so that will have to wait for another day.  Anyway, best performance should be available with the device connected straight to the port and that should degrade with an inferior cable being used to transmit the 0s and 1s back and forth.

So, for this experiment I used:

  • My standard PC which is fitted with a USB 2.0 expansion card based on the NEC chipset.
  • A 1Gb disgo pro USB flash memory device.  The box rates this device as having 24Mb/s write speed and 14Mb/s read speed.
  • A no-name USB A to A M/F extension cable (this cost pennies).  This is 60cm long.
  • A SKYcable blue/red LED USB indicator.  This is the kind of thing that you fit between the device and the port that glows when the port is inactive and flashes when data is transferred.  It's partly a "cool" and "WOW!" feature but it also does make finding ports at the back of the PC or a loose cable dangling a lot easier.  The instructions make no reference to this being USB 1.1 or 2.0 so this is also worth a look at.
  • Speed testing would be carried out using two applications

The Tests

The tests are simple and consist of three parts:

  1. Connect the disgo pro to the USB 2.0 port directly and test
  2. Connect it with the cable and test
  3. Connect it with the cable and the SKYcable USB indicator and test

Files moved using Disk Bench would consist of a 1Mb file, a 100Mb file and a 500Mb file.

All tests were carried out under normal PC running conditions to simulate real-world use.  No modifications were made and no applications of services switched off.  Conditions were similar for all three tests.  Disk Bench results averaged over three runs.

The Results

The results are very interesting indeed.

First, the results using Disk Bench.

PC to disgo pro (Mb/s)

  Direct connection Cable connection Cable & LED
1Mb 4.763 4.763 4.001
100Mb 8.988 9.510 8.322
500Mb 7.839 7.552 8.655


disgo pro to PC (Mb/s)

  Direct connection Cable connection Cable & LED
1Mb 9.092 12.502 14.288
100Mb 14.925 16.477 14.474
500Mb 14.724 14.763 14.318

Results here are somewhat inconclusive.  While it would appear that PC to disgo pro transfer (in other words, write speed) of 1Mb and 100Mb files are adversely affected by the cable + LED indicator combination (by an average of 1.18 Mb/s for the 100Mb file), transfer of files from the disgo pro to the PC (read speed) seems to be only slightly affected by the LED indicator.  Cable quality in both tests seems to have little effect, and actually seems to improve performance when transferring 100Mb files.

The results from the full sequential read test carried out by HD Tach RW are more conclusive.  Here are the results.

Direct connection

Click for larger image - use back button to return

Cable connection

Click for larger image - use back button to return

Cable + LED

Click for larger image - use back button to return

Here we get the following results:

Connection Average read speed (Mb/s)
Direct 16.8
Cable 16.7
Cable + LED 16.6

Here we see that a direct connection offers around 100Kb better average read speed than a cable connection and about 200Kb better than the cable + LED combination.


So, does cabling make a difference?  Answer - yes, well, maybe, a little.  

If you are a standard user, then I doubt seriously that any cable that works and is constructed well enough so that ends don't fall off will work and you're unlikely to notice any difference.  If you want pretty cables of cables with warranty then feel free to pay the money but to be honest you'd be far better putting the money towards better hardware that attaches onto the cable (the disgo pro I used here being a good example).

However, if you are a speed freak and want everything to be as fast as possible, then paying the extra is something you'll do.  

Another benefit of high-quality cables not covered here is their robustness, long life and warranty, however for the price that you will pay for one cable you could probably buy a dozen cheaper cables that are just as adequate.

Future tests

  • Compare different brands of cable
  • Compare and contrast the effects of cable length (the USB specification limits the length of a cable between full speed devices to 5m or approximately 16ft 5inch.  For a low speed device the limit is 3m or 9ft 10inch).

Adrian Kingsley-Hughes
Last updated: April 4th 2004
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