Over the last few years, the Universal Serial Bus (USB) has become the universal interface. Starting in 1995, when USB 1.0 could only transfer 12 Mbps (Megabits per second), the standard started up slowly. But when USB 2.0 came along in 2000, with its 480 Mbps, the days were numbered for PS/2, serial, parallel, and even the FireWire interface. So, why hasn't USB 3.0, also known as SuperSpeed USB, with its 5 Gigabits per second (Gbps), become the interface of choice since its introduction in 2008? Well, there are several reasons.
Why you want USB 3.0
This is pretty simple. It's fast. It's even faster than eSATA (External Serial Advanced Technology Attachment). When I tested USB 3.0 against eSATA last year, I found that in practice neither was quite as fast as their specifications suggests -- on reads my USB drive averaged 90 MBps, while the eSATA drive came in at 75 MBps. But, when it came to writing to the disk eSATA still processed data at 75 MBps while the USB drive dropped to 62 Mbps.
USB 3.0, like the other USB standards before it, also has the advantage though of being able to supply power to its devices. An eSATA device requires a separate power supply.
The USB 3.0 standard also uses interrupts instead of “polling” when a device is plugged in. With polling, when a USB device is plugged into the port, the computer keeps checking on it to see if needs anything. This keeps the computer from going into low power states and can quickly drain a battery. That's bad news on a laptop. By using interrupts, USB 3.0 doesn't waste time or energy on an idle device, this in turn saves battery life.
When a device does need power though. USB 3.0 supplies 50% more power draw. That means instead of just thumb drives you can power up external drives.
In addition, even if your PC doesn't have a USB 3.0 port, you can buy a PCI (Peripheral Component Interconnect) card with two ports for about $25. There are already multiple USB 3.0 compatible external hard drives and case enclosures from vendors such as Buffalo Technologies; Seagate and Western Digital.
So, put it all together and you can see why USB 3.0 should be popular.
But it's not. It's still a fair amount of trouble to find computers with USB 3.0 built in. Today, HP, Sony, and Dell offer only a handful of PC withs USB 3.0.
Why USB 3.0 hasn't caught on
USB 1.0 and 2.0 ports and devices were interchangeable. Of course, any such combination would only go as fast as 1.0's 12Mbps. But with USB 3.0, even though the plug and PC connection look the same at a casual glance, they're not really compatible with the older models.
Instead of four wires, the USB 3.0 cable has eight wires. One is power, one is for the ground, two for USB 2.0 data ), and four wires for SuperSpeed data. If you take a closer look at a USB 3.0 cable you'll see that one edge of the plug is colored blue. The end that plugs into your USB 3.0 drive, scanner, printer, or camera, however, is not the compatible with a USB 2.0 device. So, while you can plug a USB 2.0 device with a USB 2.0 cable into a USB 3.0 port or a USB 3.0 device with a USB 3.0 cable into a USB 2.0 port, you can't use a USB 3.0 cable to connect a USB 2.0 device. Got that?
In short, you can't switch out USB cables willy-nilly if you're using USB 3.0. Since, at a quick glance you may mistake a USB 2.0 cable for a USB 3.0 one, it's a small, but vexing, problem.
By itself, that's not a big deal. Far more important is that Windows 7, even with SP1, still doesn't natively support USB 3.0. You can use USB 3.0 ports and devices of course, with the right device drivers, but in 2011, what Windows user worries about device driver compatibility? Mac users have the same problem. Even Snow Leopard doesn't have built-in USB 3.0 support. It's another annoying hitch. Ironically enough, Linux, which is always getting grief for not supporting this or the other device, is the only operating system with USB 3.0 support baked in.
On top of that, even though Intel was a member of the USB working group that helped create the USB 3.0 specification, it was only at Computex in Taiwan on May 31st 2011 that Intel finally committed to supporting USB 3.0 on an actual product line. Intel will ship the "new" USB on its Ivy Bridge chipset.
Don't get too excited yet though. Ivy Bridge, the successor to Sandy Bridge, has just had its release date moved back to March 2012. If you want a motherboard with USB 3.0 already built in sooner than next year, you can look to AMD. The other CPU chip giant has announced that its A75 and A70M Fusion chipsets will include USB 3.0. These chipsets are already shipping.
So why has Intel been such a stick in the mud? Well, Intel has its own high-speed interface agenda to push: Thunderbolt, formerly known as Light Peak, which Intel first showed at the Intel Developer Forum (IDF) in September 2009.
Thunderbolt is a fiber optic wire connection. It uses the same size connector as USB but even thinner wires. Unlike USB 3.0, which in theory can reach out to three meters with Gbps speeds but in practice goes to about two meters, Thunderbolt can transmit data up to 50 meters.
Thunderbolt can also be used with PCI Express and DisplayPort. Thus, it can be used both for devices and for display high-definition video. Intel also promises that you'll be able to power devices through it.
On top of that, Thunderbolt, although it's not here yet except in labs, can transmit 10Gb of data per second bidirectionally, twice that of USB 3.0. Need I add that it too is going to be included on the Ivy Bridge chipsets?
Unlike USB 3.0, though, which is an industry wide standard, Thunderbolt is Intel specific. So, while in many ways Thunderbolt does sound like it will better than USB 3.0, you'll only be able to use it with Intel equipment and with hardware that's been manufactured by vendors under an Intel license. Historically, proprietary inputs and outputs don't do well in the mass-market. You'll recall that, FireWire, Apple's take on the IEEE 1394 High Speed Serial Bus, never really took off even though it was far faster than its competitors.
So what's a user to do? Well, even though USB 3.0 has not taken off as quickly as many of us thought it would, I believe in the long run it will win out and become the next universal PC input/output (I/O) system. While Apple, Intel, and Microsoft have all failed to support it properly, it's still the most flexible, high-speed and open I/O out there and I foresee trouble ahead for Thunderbolt getting the kind of universal support that earlier versions of USB have gotten.