Maximizing Hi-Speed USB (USB 2.0)
Why you need USB 2.0 now and how to retrofit it to your system for maximum utility and ease of use

USB 2.0, now known as Hi-Speed USB, has quickly become the must-have variety of USB, thanks to widespread adoption by vendors of a wide variety of USB-based hardware. From inkjet printers to external drives, from scanners to keychain drives, the market is quickly becoming flooded with Hi-Speed USB devices. Even if most of your existing devices support USB 1.1 (known simply as USB), Hi-Speed USB host adapters can manage multiple devices better than USB 1.1 host adapters when equipped with the right type of hub.

In this article, you learn how to make sure Hi-Speed USB ports are enabled, what USB 1.1 devices you should attach to these ports, how to upgrade your existing USB 1.1 hubs and cables, and what to look for in a Hi-Speed USB hub which will be used to support multiple USB 1.1 devices.

Understanding USB Speeds and Levels

USB nomenclature is getting increasingly complicated with the development of two versions of USB and three speeds of USB devices. Table 1 helps sort it out for you.

Making Sure Hi-Speed USB Ports Are Enabled

Hi-Speed USB runs at speeds up to 480Mbps, compared to the 12Mbps full-speed and 1.5Mbps low-speed options available with USB 1.1 0(now known simply as USB). If you use Windows XP and try to plug a device designed for use with Hi-Speed USB into a regular USB port or hub, youll see an error message similar to the one shown in Figure 1.

Figure 1. Windows XP warns you of a mismatch between a Hi-Speed USB (USB 2.0) device and a USB 1.1 port.

This can be an unpleasant surprise if you thought you had Hi-Speed USB ports that were ready to work. Unlike USB 1.1 ports, Hi-Speed USB ports sometimes require some effort to configure, both from a BIOS standpoint and a driver standpoint.

If your system uses an Intel chipset that provides Hi-Speed USB ports, you need to enable the High-Speed USB support option. Look for this option in the USB Configuration submenu. If you dont enable this option, your Hi-Speed USB ports will work like USB 1.1 ports.

The second problem, even if your ports are already enabled for Hi-Speed USB support, is driver support. Some vendors provide Hi-Speed USB support for Windows XP as well as earlier versions on the driver CD or disk supplied with the motherboard, but other vendors do not supply a Windows XP-compatible driver.

If you use Windows XP and you dont have vendor-supplied Hi-Speed USB drivers, you need to download and install Service Pack 1 for Windows XP. Get it from http://www.microsoft.com/WindowsXP/sp1/default.asp.

After you download and install Service Pack 1, follow these steps to install Hi-Speed USB support:

1. Right-click on My Computer and open the System properties sheet.
2. Click the Hardware tab.
3. Click the Device Manager button. The device might be listed in the Other Devices category or in the Universal Serial Bus controllers category with a name similar to Enhanced USB Host Controller.
4. Double-click the device to open its properties sheet.
5. Click the Driver tab.
6. Click Update driver.
7. Let Windows search for the driver. It will find a suitable driver in the new driver collection installed as part of Service Pack 1.
8. After the driver is installed, you can use the Hi-Speed USB ports with Hi-Speed USB devices.

Using Your Hi-Speed USB Ports Wisely

After you install or enable Hi-Speed USB ports, its tempting to plug all of your existing USB devices into the faster ports. However, you should keep low-speed (1.5Mbps) USB devices such as keyboards and mice or other pointing devices connected to your systems original (built-in) USB ports. These devices dont produce enough traffic to benefit from the superior management of Hi-Speed USB.

Theres a second reason to keep your USB keyboard plugged into your computers built-in USB ports instead of those provided by an add-on host adapter: depending upon your system, your USB keyboard might not work until Windows starts if it is plugged into an add-on card instead of the motherboard.

Upgrading Your USB Infrastructure: Hubs and Cables

USB hubs and cables have been popular since the first USB 1.1 ports were introduced several years ago. Hubs serve three purposes:

• USB hubs enable you to make USB ports available in a more convenient location than the rear of your PC (such as on top of your tower PC or on your desk)
• USB hubs extend the permissible distance between a USB device and the computer by providing a short-distance connection between the device and the hub
• USB hubs enable a single USB port to support multiple devices

Unfortunately, Hi-Speed USB ports require Hi-Speed USB hubs. If a USB (1.1) hub is plugged into a Hi-Speed USB port, the ports in the hub are limited to the same 12Mbps speed as if they were plugged into a USB port. When you upgrade to a Hi-Speed USB host adapter card or motherboard with Hi-Speed USB ports, you need to replace your existing USB hubs.

You can add a conventional Hi-Speed USB hub which plugs into the rear of the system and uses an AC adapter, but if you want to reduce desktop clutter and eliminate the need for yet another AC adapter, consider a drive bay-mounted Hi-Speed USB hub. These are produced by companies such as Belkin (www.belkin.com), SIIG (www.siig.com), and others. Figure 2 shows how SIIGs four-port Hi-Speed USB hub (C) works with its companion five-port Hi-Speed USB host adapter card (A) and a desktop USB hub (F).

(Click to enlarge)

Figure 2. The SIIG Hi-Speed USB host adapter card (top left) can connect to the SIIG Hi-Speed USB host adapter (top right) and to a desktop USB hub (bottom center) with USB or Hi-Speed USB A to B cables.

In Figure 2, B is a Hi-Speed USB A to B cable, while E is a standard USB A to B cable. D is the Y-splitter cable used to borrow power from a Molex power connector used to power hard disks and optical drives. G is the power cable for the desktop hub (F). Figure 3 provides a close-up view of the A and B connector ends on a typical USB cable.

Figure 3. Both USB 1.1 and Hi-Speed USB cables for devices have an A-connector (top) and a B-connector (bottom). The A connector plugs into USB ports on add-on cards and systems, while the B connector plugs into external devices such as hubs and printers.

In theory, any USB cable should be compatible with both USB 1.1 and Hi-Speed USB ports and devices. However, cables made especially for Hi-Speed USB typically feature better shielding than USB 1.1-compliant cables. High-quality shielding is necessary to handle the fast signaling levels supported by Hi-Speed USB. Consequently, some experts estimate that only 30% of cables marketed as USB 1.1 will provide top-speed performance with Hi-speed USB ports and devices. For best results, you should plan to replace USB cables you plan to use with your new Hi-Speed USB ports and devices with Hi-Speed USB cables.

Choosing the Right Hub for Use with Multiple USB 1.1 Devices

One of the often-mentioned benefits of moving up to Hi-Speed USB devices is Hi-Speed USBs ability to cope with multiple streams of USB 1.1 data. This capability depends upon the presence of a feature know as a transaction translator (TT) in a Hi-Speed USB hub. The TT places the data streams from USB 1.1 devices into the Hi-Speed USB data stream. To provide the superior functionality of Hi-Speed USB with USB 1.1 devices, each port on a Hi-Speed USB hub needs a separate TT. Unfortunately, many hubs use a single TT for all the ports, and these hubs slow down drastically when two or more USB 1.1 storage devices running at 12Mbps are in use at the same time.

Some models of Hi-Speed USB (USB 2.0) Hub controller chips made by Cypress Semiconductors (www.cypress.com) SMC (www.smsc.com), and VinChip Systems (www.vinchip.com) include a multiple-TT design (there may also be others which include this feature). However, its difficult to determine from packaging or from online writeups whether a particular Hi-Speed USB hub uses a controller chip which supports multiple TTs. If you need to connect multiple 12Mbps USB devices (printers, scanners, keychain or other external drives, and so on) to a Hi-Speed USB port via a hub, you should check with the vendors of the hubs you are considering to determine which hubs support this feature.

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