Help me - I don't understand USB entries in Device Manager

I have two ASUS P4B533-VM MOBOs The MOBO has three USB 'headers'
connected to six ports (two per header). The DeviceManager entries
for USB in each differs and I wonder why.

One has the following (note that there are four pairings). The other
has similar but only three pairings. Can anyone suggest what this
means?

Thank you

Class: Universal Serial Bus controllers
Device: Intel(R) 82801 DB/DBM usa Universal Host Controller - 24C2
Resource:
IRQ: [00000016]
10: [0000D800 - 0000D81 F}
Device Drivers:

Class: Universal Serial Bus controllers
Device: Intel(R) 82801 DB/DBM usa Universal Host Controller - 24C4
Resource:
IRQ: [00000019J
10: [OOOOD400 ~ 0000041 F]
Device Drivers:

Class: Universal Serial Bus controllers
Device: Intel(R) 82801 DB/DBM usa Universal Host Controller - 24C7
Resource:
IRQ: [00000018}
10: [00000000 ~ 0000001 F]
Device Drivers:

Class: Universal Serial Bus controllers
Device: Intel(r) 82801 DB/DBM usa 2.0 Enhanced Host Controller - 24CD
Resource:
IRQ: [00000023]
MEM: [FEBFF400 - FEBFF7FF] Device Drivers:

Class: Universal Serial Bus controllers Device: usa Root Hub No
resources used. Device Drivers:
Class: Universal Serial Bus controllers Device: usa Root Hub No
resources used. Device Drivers:
Class: Universal Serial Bus controllers Device: usa Root Hub No
resources used. Device Drivers:
Class: Universal Serial Bus controllers Device: usa Root Hub No
resources used. Device Drivers: