[opendtv] USB 3.0 guns for Firewire
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 20 Sep 2007 10:32:45 -0400
From the beginning, it was predictable that USB and 1394 were ultimately
going to solve exactly the same problems. Eventually, these things do
shake out. Except that I would have chosen 1394 over USB, since it was
already the faster of the two, and did not require a bus master. But
these things don't always evolve in logical ways.
Bert
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USB 3.0 guns for Firewire
Rick Merritt
(09/18/2007 11:06 PM EDT)
URL: http://www.eetimes.com/showArticle.jhtml?articleID=201807389
SAN FRANCISCO, Calif. - Intel Corp. announced it is working with a
handful of companies on a specification that could push the USB's
theoretical throughput beyond 4 Gbits/second, ten times its current
rate. The USB 3.0 spec aims to deliver 300 Mbytes/second of usable data
at the applications level and add new quality of service capabilities
that could challenge the 1394 interconnect also known as Firewire.
At their inception in the early 1990's, USB aimed at keyboards and mice
with a 1.1 spec running at less than 12 Mbits/s. Firewire targeted audio
and video applications such as camcorders at 100 Mbits/s and faster.
But over time USB has seen widespread adoption and swung to speeds
approaching 480 Mbits/second while Firewire has been much less broadly
adopted. With the latest move announced at the Intel Developer Forum
here USB aims to leapfrog Firewire.
Aiming at long term expandability, Intel engineers have tested a basic
version of the new protocol in software simulations at 5 and 25
Gbits/second, said an Intel engineer. The link is media agnostic and
will run over copper and optical cables.
The interconnect, also called SuperSpeed USB, aims to serve any
flash-based device including USB drives, camcorders and media players.
One design goal is to keep abreast of the transfer speeds of flash
chips.
"We don't want to be the bottleneck in the system," said Jeff
Ravencraft, an Intel executive overseeing the USB 3.0 initiative.
Hewlett-Packard, Microsoft, NEC, NXP and Texas Instruments are helping
define the new spec which will be put up for a design review at a
two-day event in San Jose in November. Intel said the group will issue a
call for contributors to the final spec soon. It hopes to finish the
spec early next year and see first silicon implementing it emerge in
early 2009.
USB 3.0 will adopt a new physical layer using two channels to separate
data transmissions and acknowledgements to hit its higher speed targets.
In place of the polling and broadcast mechanisms used in USB today, the
new spec will employ a packet-routing technique and only allow data
transmissions when end devices have data to send.
The new link also will support multiple flows per device and is capable
of maintaining separate priority levels for each flow. The capability
could be used to end interrupts that cause jitter in video
transmissions. The flow mechanism also can enable native command queuing
to optimize disk drive traffic.
Proponents said USB 3.0 could supplant Firewire which they said is
losing backing from companies such as Sony who have switched to USB 2.0
for products such as camcorders. "Most people see 1394 as declining,"
said Masami Katagiri, a senior engineering manager helping define USB
3.0 at NEC Electronics America Inc. (Santa Clara, Calif.)
"It seems like a big jump for them and such a different approach that it
could be a challenge to get silicon out in early 2009," said James
Snider, executive director of the 1394 Trade Association that defines
Firewire.
A variety of products, including many external hard disk drives, are now
using 1394 to deliver connections offering a maximum physical layer
throughput of 800 Mbits/second. The group hopes to finish a spec early
next year to push that to 3.2 Gbits/second, Snider said.
The new speed grade will continue to use the same cables and connectors
defined for the current 1394b standard. Those cables and connectors have
been rated for speeds up to 10 Gbits/s. The trade association is
reviewing proposals for a 10G Firewire spec, he added.
Apple Inc. has been invited to join the USB 3.0 promoters group but has
not yet responded to the invitation. Apple has been a longtime supporter
of Firewire which it uses in all its iMacs for media applications
currently beyond the reach of USB.
Katagiri of NEC said Apple could be forced to switch from Firewire to
USB 3.0since Intel is now its major silicon supplier and will be using
USB 3.0 eventually in its chip sets.
Nevertheless, USB 3.0 has its challenges. Katagiri said the spec
probably will have to reduce the five-meter reach of USB 2.0, perhaps to
as little as two meters. In addition, host controllers will have to have
significantly more intelligence because they manage routing of data
transmissions.
On the other hand, the USB 3.0 group is looking at new techniques for
supporting isochronous data transmissions that could provide an edge
over features found in Firewire, he added.
For its part, the 1394 has been studying use of Firewire over distances
as great as 100 meters on Category 5/6 cable and optical fibre, Snider
noted. It is also exploring versions for use in the home and car over
coax cables.
Whether the USB group can leapfrog the throughput, quality of service
and time to market of 1394 remains to be seen. Many of the same
participants running the USB 3.0 initiative also oversee the wireless
USB work based on ultrawideband.
"We have a lot on our plate," said Ravencraft who leads both efforts for
Intel.
The wireless USB initiative announced today its targets for a version
1.1 of its specification. The new version raises throughput targets from
480 Mbits/second to 1 Gbit/second over three meters.
Katagiri of NEC said the throughput targets are a stretch because most
companies are still shipping first-generation wireless USB devices only
hitting rates of 40 Mbits/second.
"We have to make the protocol more efficient," Katagiri said. "If we go
for a Gbit we will need to deliver at least 500 Mbits/s," he added.
The 1.1 spec will support band groups at 6 GHz and above in addition to
the 3-4 GHz bands supported by wireless USB 1.0. It aims to lower power
consumption by an undisclosed amount. It also will adopt the techniques
of near-field communications for letting two devices identify themselves
to each other with a simple contact.
Currently the USB Implementers Forum has certified a handful of
notebooks and hubs for the 1.0 spec. The WiMedia Alliance is expected to
certify the first 1.0 products shortly.
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