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Publisher7.1 High-Capacity FDD Types
Although many
types of high-capacity FDDs have been announced, and some have even
been produced in small numbers, the only high-capacity FDDs that have
achieved even moderate market penetration are the Iomega Zip Drive
and the Panasonic SuperDisk Drive. The following sections detail
these drives.
7.1.1 Iomega Zip Drive
The Iomega
Zip Drive is the direct descendant of the Iomega Bernoulli Box, a
mass storage device that was a popular (and expensive) add-on for IBM
XT/AT systems and compatibles throughout the 1980s. The first
Bernoulli boxes used 8-inch 10 MB cartridges. Later models used
5.25-inch cartridges that ranged from 20 MB to 230 MB. Various
single- and dual-drive Bernoulli Box models were available, but they
never achieved mass-market success because the drives were very
expensive and used expensive cartridges that required periodic
replacement.A Bernoulli cartridge was in effect a large floppy diskette contained
in a plastic shell. As the disk rotated, differential air
pressurecalled the Bernoulli Principle, hence the
namepulled the disk toward the heads, with which it remained
in contact while the drive was spinning. This meant that Bernoulli
cartridges wore out relatively quickly, and many users spent as much
on cartridges as on the drive itself. But, in the days when hard
drives were slow and held only 10 or 20 MB, the Bernoulli Box was a
reasonable solution for people who needed a lot of disk storage for
databases and similar applications. The Bernoulli Box was as fast as
a hard drive, or nearly so, and one could expand storage simply by
buying additional cartridges, a revolutionary concept in those days.By the late 1980s, as hard drives increased in size and performance,
the Bernoulli Box was becoming obsolescent. But the technology was
still sound, so Iomega repositioned the Bernoulli Box in a smaller,
cheaper form as supplemental rather than primary storage, and named
it the Zip Drive. In effect, Iomega shrunk the Bernoulli Box and its
cartridges to a standard 3.5-inch form factor. The Zip Drive was
inexpensive, had large capacity and reasonably high performance for
the time, and so became a popular accessory for those who needed
removable, transportable storage.As the 1990s ended, the Zip Drive had fallen prey to the march of
technology, just as the Bernoulli Box had a decade earlier. Although
Iomega increased the capacity and performance of the Zip Drive
marginally, other technologiesnotably CD
writersprovided superior and less-expensive solutions in the
niche formerly dominated by the Zip Drive. The Zip Drive might
ultimately have replaced the standard floppy drive but for two
problems: its inability to function universally as a boot floppy in
standard systems, and the very high cost of Zip disks. Had those
problems been addressed, the Zip Drive might have become ubiquitous.
They were not, and so the Zip Drive is rapidly fading from the scene.As the market for the Zip Drive disappears, Iomega still claims
"millions of users" for the Zip
Drive. That sounds impressive until one realizes it means that 1
billion or more systems have been built without Zip Drives. So, in
fact, although millions of Zip Drives have been sold, they are now
seldom installed in new systems and have become very much a niche
product. But those millions of drives do make the Zip Drive a
standard of sorts, to the extent that there can be any standard in a
market as fragmented as high-capacity FDDs.Iomega currently produces three versions of the Zip Drive, which are
detailed in the following sections.
7.1.1.1 The Zip100 Drive
The Zip100
Drive has been made in numerous variants, including internal
ATAPI/IDE and SCSI models and external parallel port, SCSI, and USB
models. Iomega once produced the Zip Plus model, which had both SCSI
and parallel port interfaces, but that model is no longer made. In
addition to the standard internal models, Iomega produces several
specialized internal IDE units designed to fit particular notebook
systems. Various third-party manufacturers have produced internal and
PC Card models for specific notebook computers.Unfortunately, Zip Drives cannot read, write, or boot from standard
3.5-inch 720 KB or 1.44 MB floppy disks, which makes it impractical
to use them as the sole floppy drive in most systems. Zip100 drives
use a 3.5-inch disk cartridge that's about twice as
thick as a standard 3.5-inch floppy diskette and stores a nominal 100
MB. Zip100 disks can be read and written by Zip100 and Zip250 drives,
but Zip100 drives can use only Zip100 disks. The Zip750 Drive can
read Zip100 disks, but not write them.
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disks, Zip disks must be formatted before data can be stored on them,
although preformatted Zip disks are readily available. You can format
a Zip disk in one of two ways. A long format requires 10 minutes or
more and corresponds to a full format on a standard floppy disk. The
long format actually formats the entire disk and verifies the
surface. A short format requires only 10 seconds or so, and
corresponds to a Quick Format on a standard floppy disk. The short
format simply zeroes out the FAT and root directory without actually
formatting the disk or verifying its surface. As with standard
floppies, a short format can be done only on a disk that has
previously had a long format done on it.Regardless of
interface, all Zip100 drives provide track-to-track, maximum, and
average seek times of 4 ms, 55 ms, and 29 ms, respectively. Because
all Zip100 drives spin at 2,941 RPM, average latency is about 10.2
ms, yielding average access times of about 39 milliseconds, much
slower than a hard drive but noticeably faster than CD and DVD
recorders. The typical start time for Zip100 drives is about three
seconds, which is the delay between inserting a disk and when that
disk can be read or written. Overall, regardless of the interface,
Zip100 drives "feel" somewhat
faster to us than standard floppy drives when reading or writing one
or a few small files, and much faster when writing many (or large)
files.The sustained transfer rates, burst transfer
rates, and average throughput of Zip100 drives vary according to
interface:
- All Zip100 drives
provide a minimum sustained transfer rate of 0.79 MB/s, which is
determined by the drive mechanism.All Zip100 drives have a potential maximum sustained transfer
rate of 1.40 MB/s, again determined by the mechanism and internal
interface, but in practice only the ATAPI/IDE and SCSI models are
likely to achieve anything near this rate. In our experience,
parallel models provide slower sustained transfers, much slower if
the parallel port is an older model or is misconfigured. USB models
are limited by the USB interface to 12 Mb/s, which translates to a
maximum sustained transfer rate of 1.20 MB/s.The burst transfer rate of Zip100 drives
is limited by the internal interface to 26.7 Mb/s, but again only the
ATAPI/IDE and SCSI models are likely to come close to that rate. The
parallel and USB models are limited by their interfaces to less than
~20 Mb/s and 12 Mb/s, respectively.Iomega specifies the typical throughput for all Zip100 drives
as 60 MB/minute, except the parallel model, which it specifies as 20
MB/minute. Based on our own experience, those numbers may be a bit
high. Using an ATAPI/IDE or SCSI Zip100 drive, it typically takes us
between two and five minutes to copy a full disk to or from a fast
hard drivenoticeably slower than the rated
throughputand it takes much longer if many small files are
being copied. We also find that the parallel and USB models are
correspondingly slower than their rated throughput in real-world use.
7.1.1.2 The Zip250 Drive
When the
Zip100 Drive was introduced, its capacity and performance were
reasonable for the time. In those days of smaller hard drives, many
people could back up their entire hard disks to one or two Zip100
disks. But as the years passed, faster systems with larger and faster
hard drives were introduced and newer versions of applications
programs continued to generate larger and larger datafiles. Iomega
realized that the Zip100 Drive was fast becoming too small and too
slow to be useful for many users, so it introduced the Zip250 Drive,
which provides more than twice the capacity and somewhat higher
performance.The Zip250 drive has been made in the same interfaces as the Zip100
Drive: ATAPI/IDE, parallel port, SCSI, and USB. Iomega also produces
PC Card and FireWire adapters that allow the USB Zip250 Drive to be
used with those interfaces. Like the Zip100 Drive, the Zip250 Drive
cannot read, write, or boot from standard 1.44 MB diskettes. The
Zip250 Drive accepts both Zip100 disks and Zip250 disks, although
we've found that using Zip100 disks negates the
performance benefits of the Zip250 Drive.The Zip250 Drive uses the same rotation rate as the Zip100 Drive, and
provides comparable seek and access times with one exception. The USB
Zip250 Drive specifies average seek time as less than 40 ms,
noticeably slower than the other models. ATAPI/IDE, parallel port,
and SCSI Zip250 Drives specify sustained transfer rates of 1.2 MB/s
minimum and 2.4 MB/s maximum, although in our experience the parallel
port model in fact has about half the transfer rate of the SCSI and
ATAPI/IDE models. The USB Zip250 Drive provides maximum sustained
throughput of 1.4 MB/s when using the USB interface, 0.9 MB/s with
the PC Card adapter, and 2.3 MB/s with the FireWire adapter.
7.1.1.3 The Zip750 Drive
When the
Zip250 Drive was introduced, we thought the Zip Drive had reached its
limits. Iomega proved us wrong by introducing the Zip750 Drive, which
triples the capacity and throughput of the Zip250 Drive.The Zip750 drive is available with ATAPI/IDE, USB, and FireWire
interfaces. Like the Zip100 and Zip250 Drives, the Zip750 Drive
cannot read, write, or boot standard 1.44 MB diskettes. The Zip750
Drive reads and writes Zip750 and Zip250 disks, and reads Zip100
disks.The Zip750 Drive spins disks 25% faster than the Zip100 or Zip250
Drive, and accordingly has an average access time (seek plus latency)
of a couple of milliseconds faster than older models. The higher data
density and rotation rate of the Zip750 allow a sustained transfer
rate of 7.3 MB/s, three times that of the Zip250, when using the
ATAPI, USB 2.0, or FireWire interface. When used with a USB 1.1
interface, the Zip750 Drive transfers data at only 0.9 MB/s, but that
is a limitation of the interface rather than the drive. The
difference in transfer rates between the Zip100/250 Drives and the
Zip750 Drive is quite noticeable. To us, a Zip 100 or Zip250 Drive
feels like a fast floppy drive, whereas a Zip750 Drive feels like a
slow hard drive.Despite the faster performance of the Zip750 Drive, we think it is
likely to sell in small numbers because the Zip750 lacks
compatibility with the Zip100 drive and because Zip disks remain very
expensive per byte stored. If you must have a Zip Drive, the Zip750
Drive is the one to get, but we suggest you think carefully before
you buy any Zip Drive at all.
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7.1.2 SuperDisk Drive
The only
serious competitor to the Zip Drive in the high-capacity floppy drive
segment is the SuperDisk Drive, which was developed by Panasonic,
Compaq, Imation, and others. SuperDisk Drive disks closely resemble
standard 3.5-inch 1.44 MB diskettes, but are distinguishable by their
triangular media shutter and trapezoidal labeling space. SuperDisk
disks can be read and written only in a SuperDisk Drive.The SuperDisk Drive was intended to be a universal replacement for
the standard 3.5-inch 1.44 MB FDD, a goal that it failed to achieve.
The SuperDisk Drive was originally available only in the 120 MB
LS-120 model. In 2001, Panasonic finally began shipping the
long-promised 240 MB LS-240 model to OEMs. Although a few system
makers, notably Compaq, bundled SuperDisk Drives with some models,
the SuperDisk Drive has always been a distant second to the Zip Drive
in popularity.
