Making your peripherals play nicely
August 2, 1999
by Stan Miastkowski
(IDG) -- Does this scenario sound familiar? You've just bought a brand-new peripheral--removable-media drive, CD-Rewritable drive, tape backup drive, whatever--that hooks up to your PC's printer port. Like most parallel port peripherals, it has a pass-through connector that lets you hook up your peripheral and your printer at the same time. But then things go downhill fast. The peripheral doesn't work, or works at the speed of a racing snail. And your printer just sits there, or spits out reams of incomprehensible gibberish that looks like something from an alien spaceship.
You've got a dreaded parallel port compatibility headache, a not-uncommon malady, as parallel port peripherals remain one of the popular add-on purchases for PC users. The bottom line is, printer ports were designed for printers. But their capability to transfer data at relatively high speeds makes them irresistible to peripheral makers who design easy-to-hook-up peripherals. It all started about five years ago with the seminal (and now ubiquitous) Iomega Zip drive.
Early parallel port peripherals didn't cause many problems--but lately, user complaints have become more common. Why the change?
"It's a can of worms," according to Mike Ludgate, director of new product development for Iomega. And the problems are two-pronged. Printers are more intelligent, often sending detailed status reports to Windows through bidirectional communications. This is how the printer alerts you that it's out of paper or low on toner. As this data flows through the parallel port peripheral, it can get confused or even stop in its tracks.
Iomega parallel drives have a reputation for a minimum of compatibility problems, but Ludgate says the company extensively tests peripherals from other manufacturers and often finds devices that "grab the parallel port and won't let go," causing printer failure the next time you try to print. And the only way around it is to shut down your PC and restart.
Printer manufacturers are concerned about the problem, too, because their technical support lines often take the trouble calls. A major problem is the lack of a standard for the way parallel port peripherals access and control a PC's printer port, says Donald Burr, a product manager with Epson America.
"There are so many variations of products that hook up to a printer port and allow pass-through connections to our printers that we can't test them all," he says. Burr's suggestion for the best way to eliminate compatibility issues: "Use USB peripherals instead."
Under the Printer Port Hood
Part of the reason for parallel port peripheral problems is in the relatively complex communication process that occurs when you turn on your PC. Your PC's BIOS--the essential communications layer between the PC hardware and the operating system--"asks" the I/O chip on your PC's motherboard (which controls your PC's serial and parallel ports) to report the devices that are connected to the printer point, and the way the port is set up. The process is known as a handshake.
Most of the problems that users run into with the parallel port version of the company's drives can be traced to motherboard makers who scrimp on the I/O chip, according to Martin Fishman, vice president of sales and marketing for Castlewood Systems, makers of the Orb removable-media drive. Although I/O chips are inexpensive (usually no more than a few dollars) Fishman says the hot PC competition means vendors often buy lower-cost I/O chips to save a dollar or two, setting the stage for possible problems.
Inside that innocent I/O chip is a lot more intelligence than meets the eye. It contains a library of references to different kinds of parallel port devices, plus programming code that optimizes the parallel port's speed to the speed of connected devices. Lower-cost chips lack the extensive intelligence needed for optimum setup, and make "best guesses" on configuration, Fishman says. If they're wrong, compatibility problems can result. Castlewood tries to get around possible problems with low-cost motherboard chips by bundling its parallel port Orb drives with a utility that tunes the drive to the chip's capabilities.
Unfortunately, there's no way to tell what kind of I/O chip is in your PC. Because it's almost always soldered to the motherboard, there's no way to replace it.
Setting the Port
Your PC may have only a single printer connection, but to get top performance from your parallel port peripheral and minimize the potential for printer conflicts, you need to set the port for optimal data flow. You do this from your PC's BIOS setup program. The details of accessing it vary by manufacturer, but the most common method is to press the delete key during system start-up. Somewhere in the setup--usually in the section named Chipset Features Setup or something similar--you'll find the parallel port settings. Typically, you'll see three settings:
Some PCs don't have separate EPP and ECP settings in their setup routines, opting instead for combination ports, usually marked as EPP/ECP. This is, by the way, a good indication that your PC has a high-end I/O chip, which can automatically detect the type of peripherals connected to your parallel port and can configure themselves for the optimal transfer speed.
Dodging Compatibility Problems
You can take several other steps to boost your chance of making a parallel port peripheral and an attached printer work simultaneously.
Ultimately, the best way to avoid parallel port compatibility problems is to attach only one device to your PC's printer port. But that doesn't mean you can't consider purchasing parallel port peripherals. Here are several relatively simple solutions.
You can add a second (or even a third) parallel port to your PC by purchasing an add-in card. They're relatively inexpensive and easy to install. ISA add-in cards with a single parallel port cost about $20 to $25; PCI versions (for the fastest speed and best compatibility), about $50. Dual-port cards for adding a second and third port go for about $60. Two suppliers are Lava Manufacturing and SIIG.
With most PCs now equipped with USB ports, you can also hook up a printer (but not a parallel port peripheral) to a USB port by way of a converter. Entrega Technologies' USB-to-parallel converter sells for about $50.
And with many of us using internal modems and mouse ports, many PCs have unused serial ports. Aten Technology offers several models of serial-to-parallel converters ($65 to $90) that let up hook up a standard parallel port printer. Like USB converters, they can be used only with printers, not parallel port peripherals. But assigning either your serial or USB port to your printer can free up your PC's parallel port for the exclusive use of a peripheral.
So many peripherals, so few ports
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