Strange behavior of 3rd party 30 pin USB cables

[baryon]

I have an iPhone 4S. I have an original Apple 30 pin connector, and two 3rd party ones as well. The two 3rd party cables were purchased 5 years apart in different countries, they look and feel very different, yet they both exhibit the same strange behavior: when I plug them into my MacBook Pro's left side USB port, my iPhone constantly vibrates as it toggles between charging/not charging non-stop. The battery icon will go green, then white, then green, etc, forever, changing about 5 times per second.

When I plug them into the right side USB port, the iPhone charges normally without erratic behavior. Now when I use my original 30 pin connector on either side USB port, the iPhone charges normally as it should.

When I use the 3rd party cables with a USB charger or power bank, they work fine, the iPhone charges fine. Only when I plug the 3rd party cables on the left side USB port on the MacBook Pro do I get constant erratic on/off charging.

There is nothing wrong with the USB ports on my MacBook Pro, as other devices work fine, and the original 30 pin cable works fine.

Has anyone heard of this before? What's going on? What makes a 3rd party 30 pin connector so different than a factory one?

While Lightning cables have a chip in them, as far as I know, 30 pin connectors are just simple wires connecting the 4 USB pins with 4 pins on the iPhone. How can they behave so differently?

 

[JPack]

While Lightning cables have a chip in them, as far as I know, 30 pin connectors are just simple wires connecting the 4 USB pins with 4 pins on the iPhone. How can they behave so differently?

http://www.eetimes.com/document.asp?doc_id=1321845

 

[baryon]

http://www.eetimes.com/document.asp?doc_id=1321845

That should explain it, thanks! I guess something extra happens when charging from a computer vs. charging from a regular USB charger or power bank, and this "extra" step isn't going through well with the 3rd party cable.