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- Posted on
- About USB 3
July 30, 2010, 10:50 am
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How common is USB 3 integration on current entry to mid-range
motherboards? Is lack of USB 3 likely to be a major hindrance
over the next couple of years for general desktop use?
I'd be willing to check out the situation myself except that my
ISP is in the middle of one of its frequent phases of giving
really poor service. We have no realistic alternative ISPs where
I live. So I'll appreciate inputs from those who already possess
the facts or are willing to look them up. Thanks in advance.
Re: About USB 3
Most USB 3 devices will be backwards compatible, so a USB board will still
be useful for many years, albeit slower performance. PCI add-in USB boards
are now easily had and are only a few pounds, so I wouldn't worry about it
too much. Some of the newer boards do now ship with a couple of USB3 ports
alongside 2 or 4 USB 2 ports, but it won't be standard across the board (no
pun) for a good few months yet, I would say.
Re: About USB 3
USB3 is a separate chip, soldered to a lot of new motherboards.
The chip they're using, is a NEC brand chip, with a PCI Express x1
lane interface. To run flat out, that chip should be connected
to a PCI Express x1 Rev.2 slot (500MB/sec), rather than a
Rev.1 slot (250MB/sec). The chip will work with either of
those, but if for some reason, you need all the bandwidth
available from USB3, the Rev.2 capable slot is better. Many
video card slots are Rev.2, but using a video slot for a
card like that is a bit of a waste. (Typically, the video
card slots are Rev.2 or 500MB/sec per lane, but the other
tiny add-in PCI Express slots are Rev.1. You'd have to
look hard, for exceptions.)
(USB 3 add-in card using PCI Express x1 connector - max speed on Rev.2)
At least one motherboard using that chip, has some crazy limitation
where the chip speed changes, as a function of the PCI Express slot
configuration (i.e. how you're using the other slots). But many
other motherboards will have that function fixed in speed, one
way or another. (I.e. Always stuck with Rev.1 x1 slots.)
The rumor is, that Intel is holding back on introducing USB3
on the Southbridge, and choosing to launch it at the same time
as they launch "Light Peak". AMD, on the other hand, has
integrated SATA III on their Southbridge, but hasn't offered
a USB3 native port yet. Both companies probably want to make
sure their launch is a clean one - ATI had a "slow" USB2
implementation once on a Southbridge, and they would not need
a "black eye" from repeating that experience. So both companies
are probably choosing to let NEC have its fun, before jumping in.
(NEC was also the first company to offer a USB2 chip, as far as
I know. The first USB2 driver may have been tested on a NEC chip.)
(AMD has SATA III)
There is one USB3 card, which uses a bridge chip, to get around the
Rev.2 slot issue. By using a bridge chip, the requirement
changes from x1 Rev.2 to x4 Rev.1 or Rev.2. But x4 slots aren't that
common, so you'd probably end up using a video card slot for this
card anyway. If you price around, this thing is a steal.
(U3S6 card - read all the reviews, before you buy it!)
So you can add the function cheaply, if it isn't soldered
to the motherboard. I'd probably try to get Rev.2 slots on
my motherboard, but I doubt there is enough info in adverts,
to make it easy to do that.
Using USB3, this table of calculated bandwidths, shows it
will be possible to hit 336MB/sec on a storage device. So
if you had a SATA III SSD, inside a proper USB3 enclosure,
and the UAS protocol is used, the transfer rate is supposed
to reach 336MB/sec. That would be a case, where the Rev.1 x1
PCI Express slot, at 250MB/sec, just would not do - you'd want
your Rev.2 slot at 500MB/sec for that :-) But who does
backups to a $600 SSD drive ? You're more likely to use a
125MB/sec 2TB hard drive inside the enclosure, and then it
doesn't matter what kind of slot you use for the add-in
Re: About USB 3
Thanks, Paul. That clears up a lot of things. Now I don't see any
pressing need to hunt for a USB3 mobo and probably pay a premium
price for it.
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