A: I think you're referring to the much-publicized, USB power-distribution issue.  One advantage of the Universal Serial BtLs is that power to attached peripherals is provided by the USB connector, not separate power adapters.  USB is a hub-andspoke system: You plug a hub into your PCs USB port.  Then you plug USB devices into the multiple connectors on that hub, including another hub into which you can plug still more USB devices and hubs.  You can connect up to 127 peripherals per USB port this way.

But for a USB hub to power devices properly, the wiring from the PCs port to the hub and from the hub to the peripheral must be the proper gauge (diameter) to handle up to 500 milliamps for each device.  For a USB cable running up to a meter long, the suggested wire gauge is 26 - For two-incter cables, 24-gauge wire is recommended.  For even longer USB cables, 20-gauge wire is used.

if the wire gauge is too small, there may be inadequate voltage at a USB device, which can cause the peripheral to malfunction and crash the PC.  In extreme cases, the USB device may even be damaged.

Not all hardware designers have read the USB specs carefully, and there are a number of USB cables and hub devices that do not handle power distribution properly.  Look for hubs that are specifically rated to supply 500 milliamps (0.5 amps) per device.  For more USB information, check with the Universal Serial Bus Implementers Forum (wwwusb.org), an industry group sponsored by more PAGE 76 BAY AREA COMPUTER CURRENTS

 TO USB or Not to USB

have wen the backs of a lot of PCs in my time, and the cables there are more tangled than the web of a politician's lies.  Connecting printers, PDA cradles, scanners, and mice to your PC means wrestling with a thick tangle of cords.  Pass-through ports and Y-spli"ers add to the clutter.  And because they don't work for all devices, you often have to paw through the thicket, unscrewing and replacing cables.  It's not a pretty sight.

The universal serial bus could help clear out this rat's nest.  USB ports, which have been standard on new PCs for the last year or two, can transfer data 10 times faster than parallel ports and a storming 100 times faster than RS-232 serial ports.  A single USB port can theoretically host up to 127 USB devices.  And since a USB port can supply up to five volts per periph ral, from scanners to digital cameera@, it eliminates the need for power cables and AC adapters.

That's the debit side of the balance shmt.  But USB isn’t all smooth safling.  While most contemporary USB devices work pretty much as advertisedsomething you couldn't say two years ag@there are still some pitfalls.  I installed and managed four USB-compliant peripherals recently.  The process wasn't painless, but it beat crawling around and unscrewing serial cables at the back of a dusty PC.

IS YOUR SYSTEM READY FOR USB?

Before buying a USB peripheral, make sure your system can support it.  First, check to see whether there are USB ports on your system.  Most PCs released in the last year or two have PAGE 64 BAY AREA COMPUTER

USB ports installed, either built into the motherboard or on a PCI interface card.  Apple's new imac also sports built-in USB ports.  If you don't see one or two rectangular slots somewhere on the back of your PC, chances are you dowt have USB installed.  You can get USB via a third-party PCI expansion card for your PC or a PC Card for your laptop from several vendors, including ADS Technologies and Amedia.  You should expect to pay between $50 and $70 for a USB card, but check www usbstuffcom/hubs for availability and pricing.

Nest, make sure your BIOS supports USB.  Most PCs released since 1997 have USB-savvy BIOSS.  These include PhocnixBIOS 4.0 and later, Award Plug and Play version 1.2 and later, and AMIBIOS 98.

But that doesn't mean the support is always enabled.  According to some USB vendors, a common tech-support headache is walking customers through their BIOS setups to enable USB support.  Save yourself a call and do it yourwif.  Run your PC's CMOS Setup and start looking for USB functions. @ith the Award BIOS, for e@mple, look under Integrated Peripherals for USB Support and press the Page Down key to change Disabled to Enabled.  If you're installing a USB keyboard (such as the ones from Belkin Components or Microsoft), you'll also need to enable USB keyboard support.

Finally, get the right operating system.  Many USB devices will work under Windows 95 version 4.00.950B or 4.00.950C (also known as OEM Service Release versions 2.1 and 2.5, respectively).  But some of them insist
on Windows 98. To find out what ver-sion of Windows you have , double-click the System  panel and click theGeneral tab. if the' version number is either 4.00.950B O' 4.00.950C, you're clear. To make sure  the USB Ports are being seen by Windows, click the “Device Manager tabb"and make sure there's a USB listing. (it might be under the Other devices item. If so, you're  squared away. If not, and you're running OSR 2.1 or 2.5, you'll need to run a file called Usbsupp.exe found on the Windows 95 installation CD-ROM.

How to make USB work?

Connection Basics

Connecting a peripheral device to a PC is generally  quite simple, as long as your computer is USB-ready. The first step is to be sure that your PC has USB
                  ports, that the USB bus is installed in your PC, and
                  that the ports are connected to the bus. The quickest
                  way to check USB readiness is to open Start |
                  Settings | Control Panel | System | Device Manager
                  and look for "Universal serial bus controller" as a listed device. Click on the
                  device for more detail to be sure that both a USB universal host controller and a
                  USB root hub are installed. If any of these elements are missing, you'll need to
                  refer to your PC documentation or BIOS to find how to enable the devices.

                  Windows 98 automatically loads USB support, but if you're running Windows 95
                  OSR 2.1, be sure to load USB support from the operating-system CD-ROM if
                  "Universal serial bus controller" isn't listed on your Device Manager screen.
                  With the Windows 95 CD inserted, just click on the file Usbsupp.exe found in
                  the Other/Usb subdirectory.

                  With USB support installed, attaching a device usually entails plugging it into
                  one of typically two USB ports on the back, side, or front of a PC. You should
                  connect the device with the PC and operating system running. After Windows
                  detects the new device on the USB bus, both Windows 95 and Windows 98
                  typically display an "Unknown Hardware Detected" message for a few seconds.
                  This message disappears automatically as the process continues, but it can be
                  disconcerting for novices and is the first indication that even with the improved
                  USB support, Windows 98 isn't entirely user-friendly for USB.

                  The next step in the installation process varies by device, but for those
                  peripherals that don't require their own software loaded first, the operating
                  system generally recognizes the device identification or type and asks for the
                  Windows CD-ROM. At this point Windows often displays its second, third, and
                  even fourth bits of user-awkwardness. You'll probably be asked for the
                  operating-system CD several times during the installation process. Regardless
                  of whether the required drivers have already been loaded, the installation routine
                  insists on reloading them and persists in not remembering where the Cabinet
                  files are, even after you point to the proper subdirectory the first time. The
                  silliest phenomenon occurs if you unplug a USB peripheral and then plug it
                  back into a different USB port on the same computer: Even if the device was
                  completely installed and running perfectly when plugged into the first port,
                  switching ports means you have to reinstall the drivers. We hope future
                  operating-system releases will be more system-aware.

                  Some USB peripherals, including the Epson Stylus Color 740 ink jet printer and
                  HP ScanJet 4100c scanner, require that you run included software before
                  making the initial device connection. Often you can connect the device and read
                  drivers from the installation disks directly. In testing for this article we followed
                  manufacturers' instructions and had no problems.

                  If you're attaching just one or two USB peripherals to your PC, you can do so
                  directly; once you've installed each device, you should be able to plug and
                  unplug it at will with no problems or surprises. The expansion potential of USB
                  and the growing number of peripherals, however, suggest that most users will
                  end up with more devices than USB ports on their PCs, which means using
                  USB hubs.

Hub Happiness

                  Continued from Connection Basics

                  USB hubs allow you to hook up multiple devices to
                  your computer via a single USB port, and you can
                  daisy-chain hubs for even more ports. Using hubs is
                  simple in theory, but you're more likely to be
                  successful if you understand a little about how the
                  USB bus provides data and power.

                  The aggregate USB data-transfer rate for a PC is 12 Mbps, approximately the
                  speed of a typical Ethernet LAN connection. The total power supplied via a USB
                  channel is 0.5 amps, or 500 milliamps (ma). The PC's USB controller and
                  internal hub manage the devices, using a step called enumeration, in which
                  each USB device is identified in turn, sharing data bandwidth and power as
                  required.

                  There are bus-powered hubs available that have no external AC power adapters
                  and draw all power from the PC bus, but if you use bus-powered hubs you limit
                  further connectivity levels (hubs plugged into hubs) and may even preclude
                  using more than one peripheral on a hub. With bus-powered hubs, the total
                  500-ma load may be taken up by a single device. This is particularly a problem
                  with devices that don't have their own power connectors, such as bus-powered
                  USB digital videoconferencing cameras.

                  A better idea is to use powered hubs. Not only does a powered hub add an AC
                  adapter to plug in, but good ones provide a full 500 ma per port. To determine
                  hub power required, count the USB downstream ports on a hub and multiply by
                  0.5 amps. Next look on the hub's AC adapter for the amperage rating. A good
                  powered hub would have an AC adapter rated for at least 2 amps for a four-port
                  hub and at least 3.5 amps for a seven-port hub. Having a bit more than minimal
                  power is even better, to provide the electricity to run LED status indicator
                  lamps. You'll also want to make sure the hub supports per-port switching, a
                  feature that prevents one failed device from taking down the whole chain.
                  Without it, if one device attached to a hub has a short, the whole hub and any
                  further generation hubs and devices will likely lose power. Per-port switching
                  isolates each port and shuts down only the port into which a shorted device is
                  plugged.
 

Correct Cables

                  Continued from Hub Happiness

                  One key to success in attaching USB devices is to
                  choose the right cables. Many devices come with
                  attached cables that should be connected directly to
                  PC USB ports or to hubs. Some faster devices such
                  as printers, scanners, drives, and speakers use
                  detachable cables. A detachable cable has a
                  square-end plug, which fits into the device, and the
                  more familiar flat USB connection end, which plugs into a PC or hub port. As
                  with other peripheral-connection types, the best connection is the one that uses
                  the shortest cable for the job with adequate-gauge wire and shielding.

                  Because part of the impetus of the USB specification was the need to keep
                  prices low, the specification has precise definitions of the minimum cable gauge
                  per length. Using a longer cable than indicated can cause an unacceptable
                  voltage drop, resulting in unreliable performance or connection failure. The
                  USBIF specifically forbids the use of extension cables and passive
                  pass-through connectors on devices such as keyboards or monitors because of
                  the potential for voltage drop. While some vendors have reported success using
                  extension cables, for the most reliable performance it's better not to use them.

Reality Check

                  Continued from Correct Cables

                  USB Products

                  A wide variety of USB peripherals are now available:
                  keyboards, mice, joysticks and game controllers,
                  printers, scanners, digitizers, digital cameras, video
                  cameras, speakers, modems, network connectors,
                  hard disks, removable storage devices, fingerprint
                  readers, and hubs. The USBIF maintains a list of products on its Web site
                  (www.usb.org). While the earliest devices usually included drivers to work with
                  Windows 95 OSR 2.1, often with mixed results, many of the newer USB
                  peripherals support Windows 98 only. Buyers should be aware that some
                  peripherals with multiple connection ports may purport to support both Windows
                  95 and Windows 98, but that on closer inspection they connect via USB only
                  with Windows 98 systems and require another connection--such as a parallel
                  port for a printer or analog connection for speakers--on Windows 95 PCs.

                  Reality Check

                  It sounds good, but does it work in the real world? In order to test this, we
                  devised a plan with several purposes. We wanted to see how well a selection of
                  typical USB peripherals installed individually and in multiples. We also wanted
                  to observe the installation differences between a Windows 95 OSR 2.1 system
                  and one with Windows 98 and between a native and an upgraded Windows 98
                  system.

                  Our test process involved attempting to install each USB device on each of the
                  platforms that supported it. If a device's documentation precluded use with
                  Windows 95 or specifically required Windows 98, we didn't attempt to force it to
                  work on the older operating system. We decided in advance not to call vendor
                  support lines or access Web sites in cases of problems, but we did plan to
                  check written and online documentation included with the product if necessary.

                  We tested on two desktop PCs. The first, a Micron Millennium Max 400, was a
                  native Windows 98 system with Phoenix BIOS 4.0 Rel 6.0, a 400-MHz Pentium
                  II processor, and 128MB of RAM. The second test-bed was an NEC PowerMate
                  P2166M with AMI BIOS 1.00.03, a 166-MHz Pentium MMX CPU, and 32MB of
                  RAM. We tested the devices on the NEC system with both Windows 95 OSR
                  2.1 and the Windows 98 upgrade.

                  The devices used in testing represented a cross section of USB peripheral
                  classes: a Belkin 3-Button USB Mouse (www.belkin.com), a Digital Persona
                  U.are.U fingerprint reader (www.digitalpersona.com), Entrega 4-Port and 7-Port
                  USB Hubs (www.entrega.com), an Epson Stylus Color 740 ink jet printer
                  (www.epson.com), an HP ScanJet 4100cI flatbed scanner (www.hp.com), an
                  Iomega USB Zip 100 removable storage device (www.iomega.com), a Kodak
                  DC260 Digital Zoom Camera, (www.kodak.com), a Microsoft Digital Sound
                  System 80 and Natural Keyboard Elite (www.microsoft.com), and a Xirlink C-it
                  PC Camera-Model XVP-510 video camera (www.xirlink.com).
 

Individual Device Installation

                  Continued from Reality Check

                  The Belkin mouse requires Windows 98, so we didn't
                  attempt to install it under Windows 95. On both
                  Windows 98 systems the mouse was recognized as a
                  Cypress USB mouse. The systems looked for and
                  loaded the human interface device file (Hiddev.inf) from
                  the Windows Cabinet files, and then the mouse
                  started working immediately without a restart. The
                  USB mouse and a standard PS/2 mouse worked simultaneously.

                  The Microsoft Natural Keyboard Elite also worked only under Windows 98.
                  Others have written that this keyboard can at times be made to work under
                  Windows 95 OSR 2.1, but the Microsoft Web site specifically states that the
                  USB adapter for the keyboard is supported only under Windows 98. As with the
                  mouse, the systems recognized the keyboard, requested Cabinet files, and
                  activated the device without a reboot. The Microsoft product could be used
                  simultaneously with a PS/2 keyboard, so it's a good choice for some
                  multiple-player games.

                  The Digital Persona U.are.U worked identically on all three test-beds. To install
                  this device, first you run the company's software, which recognizes the
                  operating system and automatically loads the correct drivers. Next you plug in
                  the device, help it find the Cabinet files if they're not in the default location, and
                  then run the U.are.U software a second time to initialize the device's fingerprint
                  authentication system.

                  When you run the required HP ScanJet 4100c installation software, the program
                  automatically turns off the PC to allow you to plug in the scanner, an
                  unnecessary remnant of pre-USB peripherals. You plug in the scanner and
                  restart the PC. After you reboot, the New Hardware wizard asks for the Cabinet
                  files. The scanner successfully installed on the Windows 95 system and on the
                  native and upgraded Windows 98 systems.

                  The Epson Stylus Color 740 printer supports a USB connection only under
                  Windows 98. With Windows 95 you must connect via parallel port. The
                  installation software instructs you to turn off the PC to plug in the printer, but
                  that step isn't necessary; again, it's a leftover from pre-USB peripheral
                  configuration. The printer worked fine on both Windows 98 systems.

                  The Xirlink C-it PC Camera installed and worked well under both Windows 95
                  and Windows 98. As with several of the other devices, you're instructed to
                  install the bundled software before plugging in the camera. On the Micron PC
                  the system also looked for Cabinet files, but with the NEC PC, installation
                  proceeded automatically without further user intervention in the Windows 98
                  upgraded and Windows 95 OSR 2.1 configurations.

                  After we installed the Kodak DC260 Digital Zoom Camera's software,
                  connecting the camera via USB cable was easy under both Windows 95 and
                  Windows 98 in both versions. The only glitch was a software default to normal
                  serial communications, reset via a Kodak connection preference menu.

                  You can install and use the Iomega USB Zip 100 drive without rebooting the PC
                  if you want to copy the drivers manually from the installation disk. If you run the
                  normal Iomega installation software, the system needs to be restarted for the
                  drive to be recognized. This drive worked fine with both versions of Windows 98
                  but does not support Windows 95.

                  The Microsoft Digital Sound System 80 speakers were somewhat problematic.
                  Because the speakers have both analog and audio USB connectors, you can
                  use the speakers with Windows 95, even using OSR1. But the digital
                  capabilities of the speakers are supported only under Windows 98, and then
                  fully only if the CD-ROM drive or DVD-ROM drive in the system supports digital
                  audio extraction (DAE), a capability for which the speaker software tests. On
                  the NEC Windows 98 upgraded system, the speakers supported two-way
                  volume and muting via the speaker-mounted buttons and supported on-screen
                  controls via USB connection, but the CD-ROM drive did not support DAE and
                  therefore would not play digital audio.

                  The NEC system was also able to reboot with the speakers attached via USB
                  cable--a significant factor, since that was not possible with the Micron desktop
                  system with Phoenix BIOS. As reported elsewhere by PC Magazine, it's
                  common for desktop Phoenix BIOS revisions with USB support to hang during
                  the boot sequence if any USB device with a configuration descriptor longer than
                  248 bytes is attached, as was the case with the Microsoft speakers. The
                  workaround is to unplug the speakers when you reboot and then plug them
                  back in again after the system comes up. The real answer will be a fix from
                  Phoenix.

                  The Entrega hubs loaded fine using Cabinet files on the Windows 98 systems
                  and using a driver supplied on a floppy disk on the Windows 95 OSR 2.1
                  system. It wasn't necessary to reboot the systems to start using the hubs.

Multiple Device Installation

                  Continued from Individual Device Installation

                  Windows 95 OSR 2.1: The NEC Windows 95 OSR 2.1
                  test-bed supported only five of the test devices: the
                  Digital Persona fingerprint reader, Entrega hubs, HP
                  scanner, Kodak digital camera, and Xirlink video
                  camera. With the hub installed, each of the other four
                  devices installed easily, without losing the connection
                  to any of the existing devices. Once all four were
                  installed, all the devices worked at the same time. Although Windows 95
                  supported only a limited subset of the test devices, even on a machine with only
                  32MB of RAM the system was able to run all the connected devices.

                  Windows 98 upgrade: Our NEC system with the Windows 98 upgrade
                  supported all nine peripherals plus two Entrega powered hubs, but the system
                  required the most patience of the three test-beds. We started by plugging in the
                  keyboard, mouse, Kodak digital camera, and Iomega Zip 100 drive, in order, into
                  the seven-port hub, and all worked fine. Then when we added the fingerprint
                  reader, we couldn't access the camera's CF disk. Rebooting once brought up
                  the camera and the Zip 100 drive, but the fingerprint reader wasn't active. After
                  we rebooted a second time, all five devices were active and stable.

                  After plugging the four-port hub into the remaining port on the seven-port hub,
                  we then added the Xirlink camera. Again we lost the Kodak camera, but
                  rebooting brought all devices back. Adding the speakers, scanner, and printer
                  did not cause other devices to get lost during USB enumeration, possibly
                  because these last four devices all install via their own software.

                  Once all devices were plugged in, we tried two tests to strain the system. The
                  first test entailed starting the Xirlink video-monitoring software and then running
                  the scanner or printer. In each case, the camera image on the computer display
                  went to a green screen because of a lack of system resources. After rebooting
                  and finding all devices stable once again, we attempted to use the HP copy
                  utility to scan a photo on the HP scanner and print it directly on the Epson
                  printer, attached to the same USB chain. This test didn't work, and the scanner
                  was lost, though the printer stayed active. We rebooted and switched the
                  scanner USB cable to the PC's second USB port (it was the sole device on that
                  port) and were able to run the copy utility and both scan and print via USB on
                  the same PC in one operation. Even though the scanner had to be attached to
                  the second USB port, this was an impressive demonstration of USB's ability to
                  keep track of devices working together.

                  Native Windows 98 system: The last multiple-device test was run on the Micron
                  native Windows 98 test-bed. The results of plugging the devices in one at a time
                  were similar to the process on the upgraded Windows 98 system, with multiple
                  reboots at times necessary to attain a state of stable recognition for all devices.
                  The biggest difference involved the Microsoft speakers, which, because of the
                  Phoenix BIOS problem mentioned above, had to be unplugged each time the
                  system was rebooted. After all nine devices and the two hubs were plugged in
                  and running, the system remained stable.

                  The Micron PC's CD-ROM drive did support DAE, so we started an audio CD
                  playing (with the analog cable unplugged so we'd be sure the sound was
                  coming via USB), started up the Xirlink video-monitoring software, scanned a
                  photo with the scanner, and then printed the scanned image. All during the
                  scanning and printing, we kept waving at the camera to watch for image
                  degradation and kept the CD playing so we could listen for loss of audio
                  throughput. The bottom line was that no degradation of video or audio quality
                  was noticeable, a testament to the system's ability keep track of all the content
                  and the benefit of 128MB of RAM.

                  The last test was to try the scanner copy utility on the same USB chain. Not
                  unexpectedly, the requests of the two devices conflicted, and as with the
                  upgraded Windows 98 system, the scanner was lost. As with the other system,
                  however, plugging the scanner into the Micron PC's second USB port enabled
                  direct copying from the USB scanner to the USB printer.

                  In sum, the Windows 98 native system worked similarly to the Windows 98
                  upgraded system, with the exception of a Phoenix BIOS conflict with the
                  speakers during system booting and a better ability to handle multiple data
                  streams because of the Micron PC's greater memory resources.
 
 

USB Tips and Tricks

                 Continued from Last Words: It Works!

                 Universal Serial Bus offers several important advantages over older designs. It
                 cuts costs by eliminating add-in cards and using a standard connector and cable
                 type.; it's fast; it makes adding components easier by virtually eliminating system
                 resource conflicts; and best of all, it allows up to 127 devices to be plugged into
                 one PC.

                 1. A USB-equipped PC typically has two USB ports on the back, side, or front.

                 2. If you have many USB devices, it's best to use powered hubs. Also look for a
                 hub with per-port switching, which prevents a failed device from disabling a whole
                 chain.

                 3. The USB specification calls for a two way data channel that supports device
                 hot-swapping and it has an aggregate data rate of 12 megabits per second,
                 approximately the speed of a typical Ethernet LAN connection. (The rate for
                 low-speed devices, such as keyboards, is 1.5 Mbps.)

                 4. Some devices, including keyboards and monitors, offer pass-through
                 connections. These can cause voltage drops, which might result in unreliable
                 performance. It's better to use a hub with more ports or a second hub.

                 5. No cable should be more than 5 meters long. For best results, use the
                 shortest cable practical and one with adequate-guage wire and shielding. Avoid
                 extension cables, which can cause volatage drops.
 

Sidebar: USB Dos and Don'ts

                  Continued from USB Tips and Tricks

                  Do run Windows 98. A limited selection of peripherals
                  run under Windows 95 OSR 2.1; for the widest
                  selection of devices and for the best results when
                  attaching multiple peripherals, Windows 98 is
                  required.

                  Do have your Windows 98 CD-ROM disk handy. You'll
                  probably be asked to insert the CD the first time you install each new peripheral
                  on either USB channel, even if the files or drivers needed are already installed.
                  To save time have the CD ready, or better yet, install the Windows 98 CAB files
                  in a subdirectory on your C: drive if you have room.

                  Don't use bus-powered or underpowered hubs, which can significantly restrict
                  the number of supported peripherals. Instead, use self-powered USB hubs with
                  at least 500 milliamps per channel. Hubs should also feature per-port switching,
                  so one bad peripheral won't shut down all devices on a hub, and LED indicators
                  for device status.

                  Don't use cables longer than 5 meters, and don't use extension cables or
                  connectors, including passive pass-through connectors on monitors or
                  keyboards. While extension cables and connectors are available, significant
                  signal degradation is a risk if you use them.

                  Do check that previously installed components still work after you install a new
                  USB peripheral. Our testing showed that rebooting the system after installing a
                  new USB peripheral often suffices to get everything working again, but it is
                  common for individual devices to stop working during installation of a new
                  peripheral.
 

USB Links & Resources

                  
                  USB Tips -- Help Channel TipZone
                   Make a Connection with USB -- FamilyPC
                  Are USB Ports The Wave Of the Future? -- Internet Business
                  USB is making connections -- Equip