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- USB 2.0 Hub or PCI card
November 23, 2005, 5:26 am
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Re: USB 2.0 Hub or PCI card
From a bandwidth perspective, each chip you add to the system,
has its own 480 megabit/second logic block. Now, a practical
limitation is caused by the PCI bus, which could not support more
than two USB2 devices running flat out. (Not all Southbridges
will connect their USB2 block the same way internally, so the
internal bus limitations may have been eliminated. They
don't all have to do it the same way.)
Consider your efforts to transfer files between two external
USB2 disk enclosures. With just the motherboard USB2 connectors,
and even if you were using an external hub box, the bandwidth
is limited to 480Mbit/sec total. Each drive could average
a bit less than 30MB/sec, as the total must be less than
If you use an added USB2 PCI card, the picture looks like
this. You put one drive on a motherboard connector, the
other drive on the USB2 PCI card connector. You will
end up being able to transfer more MB/sec this way, than
in the diagram above. The difference probably won't be
that big, but it should still be different.
______________________________ <-- Potential congestion
point is system busses,
| | and the connection method
| Mobo | PCI up here, may differ between
/ \ USB2 / \ USB2 modern and older chipsets.
| | | |
/\ /\ /\ /\
In most practical situations, these are non-issues, and would
give no visible improvement. (I mean, how often do you connect
two USB2 disks to a computer.) I would personally select the
USB2 PCI card myself. As Kony points out, NEC is a good chip
brand on the card itself.
You can use the picture collection on Newegg, to see what chip
is on some of the popular USB2 card types. Select "PCI to USB"
in Type, then click Go, then click "View Pic" link under each
picture. You'll need to save the picture to disk, and magnify
it with an image tool, to see the chip name.