Intel Corp and Microsoft Corp, both of the US, NEC Corp of Japan, and three other firms have jointly standardized the USB 3.0 next-generation interface, achieving transfer rates at least ten times higher than existing USB standards. The six firms have created the USB 3.0 Promoter Group to promote the standard, and plan to finalize the specifications in the first half of 2008.
Copying 25GB of Video in 70s
Several points have been revealed about the upcoming USB 3.0, namely (1) the peak data transfer rate is at least ten times that of USB 2.0; (2) connectors are downwardly compatible with existing USB standards; and (3) two new copper wire pairs have been added. Optical transfer will be added as an option for the future.
The maximum data transfer rate of USB 3.0 appears to be settling down at around 5Gbps. The target USB 3.0 transfer speed is described by Promoter Group chair Jeff Ravencraft: "USB 2.0 is capable of copying a 25-Gbyte high-definition video between equipment in 13.9 minutes, but it should only take about 70 seconds with USB 3.0." This works out at 5Gbps.
Engineers working with high-speed interfaces, however, seem to be quite worried about how radiated electromagnetic interference (EMI) will be handled with the 5Gbps data transfer rate. One engineer working at an electronic component manufacturer commented, "We were finally able to control EMI with USB 2.0 by using a variety of noise-reduction components, but it will be pretty difficult to suppress EMI at ten times that speed."
Send/Receive Lanes
The connector will retain compatibility with USB 2.0, which means that while the external shape is the same, five new pins for high-speed transfer have been added on the interior (Fig 1). When work first started on the USB 2.0 standard there was prolonged debate about whether or not to maintain compatibility with the USB 1.1 connection, the previous generation. In USB 3.0, however, downward compatibility was one of the first specs mentioned, and was assigned a high priority in standardization.
The higher speed was made possible by adding two shielded, twisted pairs for high-speed transfer, in addition to the existing signal lines: one dedicated to send, and the other to receive. Compared to USB 2.0, pumping both send and receive through one pair, it is much easier to boost data transfer rates. The Promoter Group refers to the specification as "dedicated IN and OUT lanes".
The transfer protocol has also been improved (Table 1). Until now, data transfer timing, or scheduling, was always handled by the host, which used polling to determine the timing for sending data to the device. In USB 3.0 host polling is no longer needed, and the sending device can freely set its own send timing. This slashes the time needed for polling (overhead) and provides a boost in transfer speed, while also contributing to lower power consumption.
The new spec also supports device virtualization. Multiple virtual machines (VM) running on the host (personal computer, etc) operating system can now access a single device simultaneously. Device resources in this case, such as storage capacity in an external hard disk drive (HDD), for example, are split, so that the VMs act just as if there are actually multiple devices.
Optical Transfer
Optical transfer is also scheduled to be newly incorporated in USB 3.0, but there is still a difference of opinion within the organization as to when it should be implemented.
Intel is eager to implement it, explaining that optical transfer will be advantageous in the future to achieve rates of 20 or 30 times those attained with existing USB. NXP Semiconductors of the Netherlands, on the other hand, feels that USB 3.0 should be created with copper cable first, leaving optical transfer for the future. Some people in the field have expressed curiosity as to why Intel should be so eager to implement optical transfer; there has been much speculation as to what Intel's ultimate goal is.
Intel plans to overhaul totally the architecture of the PC, including internal buses, over a period of several years, and industry sources have suggested that it will want to use optical wiring running at speeds of 10Gbps to 40Gbps. An engineer at a US manufacturer involved in developing the UB 2.0 standard believes that Intel is keen to implement optical transfer now because the firm hopes to utilize the technology in optical wiring in the future. Optical transfer is likely to remain an important topic at the Promoter Group for a while to come.
From September 2007 the Promoter Group began accepting "contributors" - corporations that want to participate in the standardization process (Fig 2). The USB 3.0 Developers Conference (a provisional name) is scheduled to be held in California this month (November 2007), with tens of contributors expected to attend.
by Hiroki Yomogita
(http://techon.nikkeibp.co.jp/article/HONSHI/20071024/141223/)
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