Waiting for the Universal Serial Bus
by Alan Zisman
(c) 1997. First
published in Canadian Computer Wholesaler, March 1997
As we?ve said in the past few issues, expect big
changes in computer
hardware design for 1997. Last issue, we saw how Intel?s MMX multimedia
processor additions were the first major addition to their processor
instruction
set since 1985?s 386.
This issue, we?re going to take you for a ride on the
bus?the PC?s expansion
bus that is. But like the city bus, a computer?s bus works more or less
the same way?but for data signals rather than for commuters. Like
commuters,
however, your computer?s data signals get on the bus at various places,
and get off at their own individual stops?but travel on a single bus
along
the way. A well designed bus makes sure that a wide variety of
passengers
can go along for the ride, and that all get where they?re going as
quickly
as possible.
Your PC has an internal bus, providing connections
between the CPU and
the RAM, as well as the classic ISA (Industry Standard) 16-bit bus,
typically
holding your sound card and modem, and the more modern, more powerful
PCI
bus, for the more demanding video, network, and hard drive connections.
PCI provides a 32-bit bus running at 33 mhz, with a peak throughput of
132 megabytes per second. Enhanced PCI versions offering (either)
double
the speed (fast) or double the width (wide) are possible, but it?s
unlikely
that we?ll see them put into effect in the near future.
Some PCs have added a SCSI connector to either the ISA
or PCI bus?plugging
in an expansion card to allow a total of seven devices to be
daisy-chained,
lined up one after another, at least theoretically with little
configuration
necessary. This matches the capability that has been standard in
Macintosh
models since the Mac Plus of 1987. SCSI, however, has never been more
than
a minority-taste on PCs, partly due to the extra configuration needed
to
get the SCSI card itself up and running, and the extra cost of the SCSI
devices themselves.
Still, PCs users have envied the ease with which Mac
owners could plug
in add-on devices to their system?s external bus. In the past year or
two,
we?ve seen the PC?s parallel port being used more and more as a sort of
poor-person?s SCSI?devices from Zip drives to QuickCams to Snappy video
capture gizmos have all plugged into the computer?s printer port. But
like
while a clever work-around, the printer port is much slower than real
SCSI?my
parallel port Zip drive, for example, is less than half as perky as a
SCSI
model.
ENTER THE USB
This is the year that we should start to see the
answer. Systems including
the new Universal Serial Bus standard promise to eliminate the need for
separate connectors for (count ?em) keyboard, mouse, game, serial, and
parallel ports?replacing all with a couple of USB ports. This should
produce
a cleaner system, with easier configuration, and better performance.
A typical PC is limited to two parallel ports and four
serial ports?and
the serial ports are limited to a throughput of 115 kilobits per
second.
By comparison, up to 127 devices can be connected to a USB port, with
data
travelling at 12 megabits per second. The four-pin USB connector
includes
two powered pins, so that plugged-in devices won?t need external power
supplies. The first device plugged in, perhaps a keyboard, will act as
a hub?additional devices will be plugged into it, not directly into the
computer. (Some USB devices, such as mice, should be hubless?able to
plug
directly into the system. And yes, Mac users, the longtime Apple
Desktop
Bus (ADB) has enabled you to plug your mouse into your keyboard?but
with
much less power and speed than USB will offer. Try plugging your
scanner
or printer into your Mac?s keyboard!)
USB supports hot plugging and plug and play?that means
that devices
can be plugged in while the computer is running, and that the operating
system will (hopefully!) identify the devices, and provide drivers as
needed.
USB hardware is included on a few models from major
manufacturers?the
IBM Aptiva S78 and Toshiba Infinia, for example. New Pentium and MMX
motherboards
have pins allowing for easy addition of USB ports, but typically (as of
early 1997), OEMs are not yet including the USB ports themselves. Here
we have a classic chicken and egg dilemma?there aren?t many USB devices
available yet? the Toshiba model ships with a USB keyboard, but the
Aptiva
or the USB-capable Sony PCV-90 don?t come with anything to plug into
the
new port. And until recently, there hasn?t been any system-level
software
support for USB?Toshiba had to write proprietary drivers.
Even Microsoft?s recent OEM-SR2 (Service Release 2)
version of Win 95
lacked USB support?now, however, Microsoft has released a patch for SR2
that provides this support. More class device system drivers are
expected
to be built into Microsoft?s two 1997 operating systems?Memphis
(Windows
97) and NT 5.0, just beginning testing for release dates later this
year.
These make it easier to add create drivers for specific classes of
peripherals?cameras,
speakers, scanners, what-have-you. A single USB connection could
support
all of these, along with high speed cable modems or ADSL modems, which
currently need to be plugged into an Ethernet card.
But even with support in the operating system, it?s
going to take a
while for peripheral devices to trickle onto the market? a number were
shown at last Fall?s Comdex, including monitors from Sony, NEC, Daewoo,
and more. Canon showed off a USB printer, while several manufacturers
showed
off keyboards. Panasonic has promised a USB digital camera and a USB
speaker,
early in 1997.
As a result of this tentativeness from the motherboard
manufacturers,
peripheral manufacturers, and Microsoft, It will be a couple of years
before
we?ll be able to entirely do away with the mess of conventional ports
and
wires.
My suspicions? USB won?t be a serious contender until
later in 1997
at the earliest. Buyers should not, however, buy a system that isn?t
USB-ready?at
a minimum, they should be able to add USB ports onto their new system
when
operating system and peripheral support becomes more of a reality. OEMs
need to make sure that the systems they?re shipping provide such
potential.
USB isn?t the only new bus architecture, however. Also
expect to see
AGP (Accelerated Graphics Port) to speed up bottlenecks in today?s
graphics
adapters, and Firewire (at least, not another three letter acronym).
Officially
called IEEE 1394 (I?ll keep calling it Firewire, thanks), it provides
an
external bus starting at 100 Mbps (compared to USB?s 12 Mbps). More on
these next month.