Usb 3.0 Information

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After a lengthy gestation period, the third generation of the Universal Serial Bus is making its way to the market. But is it already obsolete?

Consumer electronics and computer vendors used the Consumer Electronics Show this past January to launch USB 3.0, an update to the popular standard external data transfer interface. The new speed of USB 3.0 generated a lot of interest.

The Universal Serial Bus (USB) has done wonders for creating a standard interface on PCs. Prior to the USB port, PCs were a mishmash of various proprietary ports, often single-vendor efforts. There was no effective means for transferring files between two PCs. If you’ve been around PCs long enough, you remember LapLink, for transferring files between two PCs, a popular application that relied on proprietary software and a thick cable connected to the serial port.

USB freed us from proprietary solutions, proprietary software, and perhaps best of all, bent pins. Ever bend a pin when plugging in a PS/2 mouse or keyboard? It’s a recipe for a bad hardware day.

The USB standard has had long lags between revisions but made up for it with quantum leaps in speed. The first version shipped in 1996, and featured a data rate of 12 Mbits per second. USB 2.0, released in April 2000, specified 480 Mbit/s, a forty-fold increase over the 1.0 specification.

USB 3.0, also known as SuperSpeed USB, has throughput of up to 5 gigabits per second. That’s even faster than the 3Gb/sec of SATA hard drives and 1Gb/sec. of high-end networking in the home. There’s 10Gb Ethernet, which has no mass market use, and is meaningful only in data centers – not on an enterprise laptop. So unless you have one of those new 6Gb SATA drives, you won’t max the speed of a USB 3.0 cable.

As a more direct comparison, it would take 14 minutes to transfer 25GB of data over USB 2.0, but just four minutes with USB SuperSpeed.

USB is standard on every PC that ships these days. Even though yours has USB 2.0 built-in, add-in cards support USB 3.0, and there are PC Card cards for laptops as well. You can buy a PCI card with two ports for as little as $39, and a host of external drives and case enclosures. If you’re into building systems, there are also motherboards with USB 3.0 as well.

External storage in particular has embraced USB 3.0 because the new hardware standard finally allows for external drives that can operate at a speed comparable to internal drives. A USB 3.0 drive wouldn’t require an external power supply, drawing power for the drive through the USB cable. Old external drives using USB 2.0 usually required an external power supply; in some cases, they used two USB 2.0 ports at the same time to get the power and throughput they needed.

USB 2.0 was such a bottleneck that a stopgap was introduced called eSATA, which allowed for external drives that used a SATA hard drive interface. Well, USB 3.0 pretty much that out to pasture.
What’s New?

The USB Implementers Forum, which coordinated development of the spec, used the same physical plug with both USB 1.0 and USB 2.0, so it was possible to plug a 1.0 device into a 2.0 port, or a 2.0 device into a 1.0 port. In the case of the latter, the USB 2.0 device simply ran at 1.0 speed.

But with USB 3.0, even though the plug looks the same, the cable has extra wires. Because of this, it will not work in a 2.0 port. The edge of a USB 3.0 plug is colored blue so you know it’s a 3.0. The USB 3.0 cable has nine wires, compared with the five in a USB 2.0 cable, even though it’s the same thickness.

Likewise, the end of the cable that connects to a USB device, such as a printer or external drive, is also different from the old USB 2.0 connector. Because of this, you can’t use USB 3.0 cables to connect USB 2.0 devices. Also, if your drive, scanner, printer, camera, or whatever is a USB 3.0 device, then you must use a 3.0 cable.

On the plus side, you will be able to plug USB 3.0 devices and cables into the USB 2.0 ports on your current computer, but you won’t get the speed advantage.

With nine wires, USB 3.0 has two additional lanes of traffic for data, and the traffic can flow bi-directionally. USB 2.0 can only do single-direction transfers. If a device and computer were to send data back and forth, the two devices had to take turns exchanging data.

Also, USB 3.0 supports asynchronous transfers between devices. In USB 2.0, the host controller had to ask for data and then the device sent it. Imagine you want a book from someone. The USB 2.0 way would require you to ask for the book’s contents one page at a time, and would request each page one after the other. The USB 3.0 way simply hands you the book.
Power to the USB

USB 3.0 SuperSpeed has a higher power draw. A USB 3.0 device can get up to 50% more power through the port than through 2.0. This permits powering much more powerful devices instead of just little thumb drives or small digital cameras.

But another big change in USB 3.0 is very important: They ended a feature in 2.0 called polling. When a USB device is plugged into the port, the computer keeps polling the port. This keeps the device and computer from going into low power states and drains the battery at a faster rate. That’s not big deal on a desktop, but on a laptop it matters.

At one time or another you probably used a notebook running on battery power, then plugged in a USB device and left it there. Next thing you knew, the battery was at 20%. That’s because the computer kept polling the USB device, sucking up its battery power.

USB 3.0 will be interrupt-driven, so if nothing is happening with the device, the machine doesn’t poll it. If you are working on a Word document, it won’t poll the device until you actually read or write to disk. This will allow the CPU to go into a low power state and thus preserve battery life.
Your Move, Intel

Intel is a member of the USB working group but has been rather quiet about USB 3.0. In late 2009, Nvidia (no friend of Intel), told anyone who would listen that Intel would not put USB 3.0 support in its chipsets until 2011, and Intel chipsets are dominant in the x86 market (unless you go for AMD).

Later, that rumored delay date was pushed out to 2012. The motherboards and add-in cards you see now with USB 3.0 use chipsets from NEC, and other vendors are reported to be so frustrated with Intel’s foot dragging that they may do their own.

So why would Intel sabotage an industry effort in which it participates? Most likely because it has its own solution in the works, called Light Peak. Intel first showed it at the Intel Developer Forum (IDF) in September 2009 and gave an update in June of this year.

Light Peak is a fiber optic wire connection. It uses the same size connector as USB but the wires are thinner than a shoe lace, as opposed to the rope-like thickness of USB. But much more important: Light Peak can transmit data up to 50 meters. USB tops out at five meters, and that’s pushing it.

The other plus of Light Peak is its speed. It can transmit 10Gb of data per second bidirectionally, twice that of USB 3.0. At the June update, Intel showed it running on a laptop computer, streaming high-definition video while transferring multiple gigabytes of files at the same time.

Would Intel favor Light Peak over USB 3.0? Why not? It has a technically superior product that could easily be used inside computers as an alternative to the much slower SATA as well as external connectors, and Intel would get all of the royalties instead of sharing them with a consortium.

They aren’t hurting the industry by not producing a USB 3.0 chip, just inconveniencing it. Other vendors are making USB 3.0 chips, after all. And USB 2.0 is so entrenched it will take a while for mainstream support to come about.

Windows 7 does not have USB 3.0 support in it yet. There are rumors Microsoft will add native USB 3.0 to the first Service Pack for Windows 7. Currently, the USB 3.0 support requires drivers from the chipset maker, but Microsoft will reportedly make it native with SP1. The beta still has not been announced as of this writing, so at this point it’s all conjecture.

The future is going to be much faster. Which road we take is not entirely clear. It all depends on what Intel chooses to support. As a major supplier of chipsets, the direction it takes could be make or break, or at the very least a headache for one side.

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