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.
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 pressure?called the Bernoulli Principle, hence the name?pulled 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 technologies?notably CD writers?provided 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.
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.
Like standard floppy 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 drive?noticeably slower than the rated throughput?and 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.
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.
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.
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.