Classic Computer Magazine Archive COMPUTE! ISSUE 160 / JANUARY 1994 / PAGE 86

How to choose a CD-ROM drive. (includes related articles about playing audio CDs on computer CD-ROM drive and caching a CD-ROM drive) (Multimedia PC)
by Richard O. Mann

If you haven't already bought a CD-ROM drive for your PC chances are that you'll buy one soon.

Market researchers estimate that over 6 million CD-ROM drives will be sold in 1993 and a staggering 18 million will be sold in 1994. If you're one of the 18 million who'll be buying in 1994, you've got some homework to do. If you buy a drive to work with your existing sound card, you'll face the whole lineup of drives; if you buy it as part of a multimedia kit, your choices will be more limited. Even if you buy your drive as part of a kit, you'd better know something about the drive that's included - it's too easy to get stuck with less-than-adequate equipment.

The problem is that CD-ROM drives come shrouded in a cloud of technobabble: Average seek time, sustained throughput, SCSI-2, XA specs, multisession capability, and High Sierra compatibility are just some of the terms you'll see. Relying on different measures, at least three major manufacturers claim their drives are the fastest on the market, while others emphasize the particular performance specification that makes their products look the best.

There are no absolutes, and there's no way to pick out the fastest, most reliable, or overall best value. But doing a little homework to understand the terms will help you identify the drives that'll best fit into your system.

Lesson 1: Speed

Double speed. This is the most important measure and the easiest to understand. The original CD-ROM drives spun their platters at the same speed used by audio CD players. By 1992, it was obvious that simply wasn't fast enough, so drive makers upped the rotational speed, resulting in double-speed drives. Double-speed drives can still play audio CDs at the regular speed, but they can literally double the speed at which they grab data and feed it out to the computer.

Increased speed is always pleasant, but it's. essential when using Video for Windows, Microsoft's live-action video and sound program used in dozens of the most popular new multimedia CD-ROMs. If you want to enjoy the video footage in the encyclopedias, most of the atlas and travel discs, and hundreds of new discs that will appear in 1994, you need a double-speed drive. Many of the old single-speed drives will stutter when playing a long burst of video.

Unless your CD-ROMs are primarily text oriented and you're a patient sort who doesn't mind several-second delays in information flow, get a double-speed drive.

Data transfer rate. Transfer rates measure the amount of data fed from the drive to the computer bus, measured in kilobytes per second (KBps). Although most manufacturers will quote a burst mode rate (the fastest rate at which a single read's worth of data can be put out), the one that matters is the sustained transfer rate. The sustained transfer rate indicates the speed of a continuous flow of data resulting from many disc reads.

The sustained transfer rate is a function of the disc rotation speed. Single-speed drives run at 150 KBps; double-speed drives achieve at least a 300-KBps rate. Toshiba's latest drive runs at 330 KBps, and Plexstor has hit 335 KBps. In certain applications, such as ones that use Video for Windows, the increase of 30 KBps to 35 KBps can be surprisingly significant.

Average access time. Also called average seek time, this measures the time in milliseconds (ms) it takes the drive to receive a data request, move the head to the data location on the disc, and retrieve the data. it's possible to monkey with this one, because there's no real standard on how far the head has to move.

Access time is only the second-most-important measurement. Real-world use of CD-ROMs often involves sequential reads right down the data tracks, requiring little or no head movement, making the access time extremely fast. Remembering that hard disks offer access times under 20 ms, the fastest CD-ROM drive's 200-ms access time seems rather poky. But compared to the 1000-ms to 400-ms times of drives from two or three years ago, it's quite respectable. if a CD-ROM drive has an access time of 200 ms to 250 ms, it's considered fast.

CPU utilization percentage. It's important that interacting with the CD-ROM drive not monopolize your computer's CPU which needs to be doing other tasks between the times it talks to the drive. This measure isn't always published by the vendors, but it's still significant. In fact, the Level 2 MPC specifications (explained later) require no more than 50-percent utilization.

If the drive takes too much system time, everything else slows down. Higher transfer rates require more CPU time, so newer, faster drives have to struggle to keep the utilization within bounds. The standard was raised from 40 percent to 50 percent in Level 2 MPC to accommodate the new generation of superquick drives.

Buffer size. A buffer reads data ahead, stores the data on a chip, and feeds it out to the CPU when requested. Without the buffer, all reads would have to come directly from the disc, which is much slower. Buffers range from 64K to 256K. For single-user systems, smaller buffers are perfectly adequate; he larger buffers have noticeable effects only in multiuser networked sessions.

Lesson 2: Data


Originally, CDs were designed to play music. The standards for data on music discs were embodied in the "red book." When computer data came to CD-ROMs, the High Sierra or IS09660 standard (in the "yellow book") controlled the format. This standard allowed for higher speeds than audio required while still allowing playback of red book audio tracks through a separate channel to the headphones or stereo jacks on the sound card.

Video for Windows required an update to IS09660, codified in the "orange book." This standard - which wasn't given its own new name - encodes audio information into the normal computer data and ships it out to the computer bus, where Video for Windows separates it. Such interleaved audio data speeds up CD-ROM drive access; the old system ha to read the disc twice - once for the sound and once for the data.

The orange book is the current standard. The next step is the XA standard, which involves full interleaving of audio and data, with the audio then going directly to an audio chip for processing. It also provides compression of video data. The bugs aren't fully out XA yet, but drive makers are building it into their drives as it currently exists. XA requires that the software be written to the standard.

Lesson 3: Photo CD

The new Kodak Photo CD system records photographs in digital form on a CD-ROM. Kodak's Photo CD standard is a takeoff on the XA standard, making it relatively easy for drive makers to add this additional compatibility.

The buzzword here is multisession capability. Originally, a Photo CD could only be written to one time, even if the disc ended up being only partially filled. An update to the standard allows appending images to existing photos on a CD. Current drives have the extra intelligence to find second and additional sessions.

Lesson 4: MPC


The Multimedia PC Marketing Council sets the minimum hardware configuration required to successfully run software that's MPC compatible. The original MPC standard, set in 1990, has proven inadequate to support today's more demanding CD-ROM based software, so the council set the new MPC Level 2 (MPC-2) standard in the summer of 1993.

MPC-2 mandatees a 486 processor; 4MB of RAM; a 160MB hard disk; a double-speed XA-ready, multisession-capable CD-ROM drive; a 16-bit sound card; and a 16-bit Super VGA video card capable of 65,000 colors in 640 x 480 mode. The standard doesn't specify local bus, but it would be difficult to meet the required specs without it.

The CD-ROM drive must achieve a sustained transfer rate of at least 300 KBps. MPC-2 machines should be able to play digitized video in a 320 x 240 window at 15 frames per second. The fast CD-ROM drive is a key component in achieving that goal.

We're talking about a powerful computer here, one that'll set you back a fair piece of change. It's smart to buy your CD-ROM drive and sound card to match the MPC-2 specs, even if you're still running a mere 386. It'll pay off in the long run. Certainly not all current CD-ROM software requires that kind of power, but with Video for Windows entering the equation, you're going to be needing that 486.

Lesson 5: Catching the

Right Bus

Most CD-ROM drives run off a SCSI (pronounced "scuzzy") bus, usually controlled by a SCSI controller on the sound card. Creative Labs, the manufacturer of Sound Blaster sound cards and associated multimedia upgrade kits, is the most visible holdout. Sound Blaster kits control their CD-ROM drives through an IDE bus. If you plan to control your CD-ROM drive from a Sound Blaster card, you'll have to buy a compatible drive that runs from an IDE controller.

The advantages of the SCSI bus are speed, a widely known standard, and the ability to add as many as seven devices to any SCSI board. You could run a tape drive, a Bernoulli box, a scanner, a hard disk, and another SCSI device without using a slot for a controller card for each device.

Also, look for compliance with the new SCSI-2 standard.

Lesson 6: Physical


You can select either an external or an internal drive strictly on the basis of availability of drive bays and desktop space; there's no performance difference. But remember that even an external drive requires a controller card inside the case.

There are two ways to handle getting a disc into the CD-ROM drive. Most common is a caddy system, involving a removable carrier that holds the CD-HOM as it's inserted into the drive. Less common is a motorized assembly, where a metal tray slides out of the drive's housing to directly accept the CD-ROM .

Because CD-ROM drives are optical devices (they reflect laser beams off tiny spots on the disc's surface), keeping the drive clean is essential. Although the drawer-system drive manufacturers would probably dispute it, using a caddy probably reduces the risk of internal contamination of the laser mechanism. Many drives include a device that physically cleans the laser lens each time you slide a CD-ROM into or out of the drive.

Midterm Exam:

Choosing a Drive

You've now done your homework on general considerations for buying a CD-ROM drive. How do you put it together to select a drive? Try this:

1. Determine if you need double speed and low access time. Will you be using current educational and reference CD-ROMs, such as multimedia encyclopedias? If so, you need double speed. If your use will be exclusively for searching text bases and other nonmultimedia tasks, a slower drive will suffice.

2. Determine if you need the new specs, including XA and Photo CD multisession capability. Basically, if you need double speed, you might as well get the rest of it. (It's hard to find a fast drive that doesn't meet these specs.)

3. Determine which bus to use. This one's easy: Use the SCSI-2 bus unless you have or plan to buy a Sound Blaster sound card.

4. Determine the physical setup you need. To keep the drive's innards clean, choose an internal drive if possible - preferably one that uses a caddy.

Now that you know the specs you need, the choice boils down to fine distinctions between drives - such as exact speed figures - and price. You also need to determine if you want to buy the drive as part of a multimedia upgrade kit. If you don't have a sound card yet, give serious consideration to the upgrade kits, which give you a CD-ROM drive, a sound card, and usually an attractive bundle of CD-ROM titles. (If you're opting for a kit, it's not unreasonable to make your choice based on the CD-ROM titles that come with the kit.)

The Drives

In spite of the prediction that we'll be buying 18 million CD-ROM drives in 1994, there aren't many vendors manufacturing drives. As you read the ads, look at the multimedia kits and multimedia-ready computers. You'll see the same basic dozen or so drive manufacturers. Here's a summary of the product lines of several of the major CD-ROM drive manufacturers.

Toshiba XM-3401 series. Available as internal drives (XM-3401B, $695), external drives (TXM-3401E, $895), or portable drives operating with supplied parallel port adapters (TXM-3401 P, $925), these fine double-speed drives show up in many kits and multimedia systems. Toshiba 714-583-3000) touts them as the fastest on the market, based on their unmatched 200ms average access time. They also achieve a 330-KBps sustained transfer rate, which is the second fastest on the market. All three use the SCSI-2 interface and are XA ready and Photo CD multisession capable.

NEC MultiSpin family. NEC (800-NEC-INFO or 708-860-9500) introduced the very first double-speed drive, calling the technology MultiSpin. Both the internal drive (MultiSpin 84, $630) and the external drive (MultiSpin 74, $695) require a disc caddy and utilize a double-door system on the drive to ensure dust protection. Both deliver a 300-KBps sustained transfer rate with a 280-ms average access time. They're XA ready and Photo CD multisession capable, and they offer a switchable setting to either a SCSI-1 or a SCSI-2 bus. The MultiSpin 38 ($560) is a parallel-port portable drive, which loads the disc through a top door. The first double-speed portable drive, the MultiSpin 38 maintains a 300-KBps sustained transfer rate but has a slower 400-ms average access time. It can operate with an optional battery pack. NEC offers an owners of its earlier models who trade in working models of the CDR - 37 portable ($179), CDR-74 external ($249), and CDR-84 internal ($229).

Plexstor Double-Speed Plus drives. Plexstor (408-980-1838), formerly called Texel, also claims its drives are the fastest on the market, based on its 335-KBps sustained transfer rate with a 240-ms average access time. Both the internal DM-3028 ($499) and the external DM-5028 ($599) use a caddy system and have drive doors for dust protection. (The doors make using the drives a little difficult until you learn how to gently pull the door down with the lip of the caddy, once again making disc loading a one-handed task.) The drives are SCSI-2 compliant, XA ready, and Photo CD multisession capable. Plexstor drives are also available in a variety of bundles that include software, Media Vision's Pro AudioSpectrum sound cards, and speakers.

Philips LMS drives. Philips LMS (719-593-7900), formerly Laser Magnetic Storage International, is the only major CD-ROM drive manufacturer based in the United States. Its CM206 internal drive ($499) is a double-speed drive that delivers a 300-KBps sustained transfer rate and a 350-ms average access time. The CM206 uses the 16-bit PC/AT bus directly rather than a SCSI adapter, which LMS says is faster. The drive uses a motorized tray that comes out of the drive to accept a disc, rather than a caddy. An unusual feature allows playing audio Cds with a simple button push - without any special software.

Microsolutions Backpack 160550. Microsolutions (815-756-3411) makes a series of Backpack portable peripherals, including a portable CD-ROM drive ($499). The drive plugs directly into the parallel port of any computer. It's a single-speed drive, delivering a 150-KBps sustaihed transfer rate and a 350-ms average access time. It's XA and Photo CD multisession compatible and uses a top-loading, no-caddy system. Because of its slower speed, it's not appropriate for the more demanding multimedia applications, such as those using Video for Windows. If your road work, however, requires access to textual information and simple graphics, this could be a good choice.

Editor's note: Just as we were going to press, NEC announced its new MultiSpin 3X and MultiSpin 4X readers. The 3X readers are triple-speed CD-ROM drives (internal, $500; external, $600; portable, $455), while the 4X reader is a quadruple-speed CD-ROM drive (external, $995).

Multimedia Upgrade


At press time, only Media Vision,and Creative Labs were offering Level 2 MPC upgrade kits.

Media Vision kits. Media Vision (800-348-7116 or 510-770-8600) is the manufacturer of the market-leading Pro AudioSpectrum 16 sound card and related products.

The Pro 16 Multimedia System II ($1,199) is the high-end kit, featuring a double-speed NEC 84Jd-1 drive with a 300-KBps sustained transfer rate and a quick 250-ms average access time. It includes the Pro AudioSpectrum 16 sound card and the following titles: Compton's Interactive Encyclopedia for Windows, Battle Chess Enhanced, Mantis, Civilization, Macromedia Action!, Mayo Clinic Family Health Book, PC Karaoke, and Where in the World Is Carmen Sandiego? Deluxe.

The Fusion Double CD-16 (external, $799; internal, $699) features the doublespeed NEC 55J drive with a 300-KBps sustained transfer rate and a 350-ms average seek time. It's fully MPC-2 compatible. The kit includes a Pro Audio-Spectrum 16 sound card and four CD-ROM titles: Compton's Interactive Encyclopedia for Windows, Battle Chess, Arthur's Teacher Trouble, and The 7th Guest.

Creative Labs kits. Of course, Creative Labs makes the famous Sound Blaster series of sound boards. It also sells a series of multimedia upgrade kits featuring Sound Blaster sound card products. Note that the CD-ROM drives in these kits are not SCSI-bus compatible.

The Sound Blaster DigitalEdge CD kit ($999) features a double-speed, MPC-2-compatible drive with a 300-KBps sustained transfer rate and a 350-ms average access time. The drive uses a front-loading tray. The sound card is the new Sound Blaster Pro 16 with Advanced Signal Processing, a real powerhouse. The bundled software titles include Voiceassist (voice recognition software), Aldus Photo- Styler SE Photo CD software, The Software Toolworks Multimedia Encyclopedia, Microsoft Works for Windows, Microsoft Bookshelf, Macromedia Action!, and AuthorWare Star.

The Sound Blaster Edutainment CD 16 kit ($750) is built around a doublespeed, MPC-2-compatible drive with a 300-KBps sustained transfer rate and a 320-ms average access time. The sound card is the Sound Blaster 16. Creative Labs went all out in bundling software for this kit. The package includes Aldus PhotoStyler SE, The Software Toolworks Multimedia Encyclopedia, Sherlock Holmes Consulting Detective, Lemmings, Secret Weapons of the Luftwaffe, Loom, The Secret of Monkey Island, and Indianapolis 500, the Simulation.

The Final Exam:

Parting Words

Buying a CD-ROM drive to bring your computer into the era of faster multimedia applications isn't as difficult as it seems. A little education cuts through the smoke screen of letters, numbers, speeds, and compatibilities. With a little research, you'll be ready to choose one of those 18 million CD-ROM drives waiting to be bought in 1994.

How to Play Audio on Your CD-ROM Drive

Your computer's CD-ROM drive is a high-priced CD player optimized for the special needs of computer data storage, but it can still play standard audio CDs.

If all you need is a basic CD player program, you can use Windows' own Media Player (MPLAYWE.EXE). It lets you start, stop, and pause your CD, as well as move from track to track. Most multimedia kits and CD-ROM drives also come with utility programs that play audio CDs.

You can augment these basic programs with full-fledged computer CD-player programs that allow you to enter artists' names and track titles. Once you've cataloged a CD, the player remembers it. You can pick from the displayed track titles to create your own individualized program.

CD Player 3.0 (Graphical Bytes, 516-283-4473, $55) puts a familiar CD-player control panel on your Windows desktop with VCR-like control buttons. To record a CD on an audiocassette, use the fit-to-tape feature to compute how best to put the tracks onto various lengths of tape.

Sound-Works (The Software Toolworks, 800-434-3088 or 415-883-3000, $49.95) is a DOS application that runs memory resident in 15K and can be unloaded when not needed. it's old fashioned and also a tad slow to work with, but it plays CDs and catalogs your collection nicely. It comes with a Works application that serves as a graphical, icon-based menu system DOS.

How to Cache Your CD-ROM Drive

To see the value of a disk cache, try starting up Windows with your cache disabled. On my fast 486 DX2/66, it takes just over two minutes to load Windows without a cache. With SMARTDRV, the relatively poky Microsoft cache utility supplied with Windows and DOS, the same task takes only 37 seconds.

The slowest drive on your system is the CD-ROM drive; caching it should accelerate it to warp speed. Unfortunately,. SMARTDRV doesn't cache CB-ROM drives; you need a third-party program fo that. I looked briefly at three of them.

Super PC-Kwik (included in Winmaster 1.5 from PC-Kwik, 800-274-5945 or 503-644-5644, $129.95) is the slowest because it's the most conservative with your data. It doesn't default to delayed disk writes and request sorting, as the others do. It's also difficult to install, requiring you to somehow get its driver loaded physically within 64K of the CD-ROM driver. On one system, I couldn't get it to work at all; on another, it took a half-dozen tries before I got it loaded properly.

Lightning CD (Lucid 800-925-8243 or 214-994-8100, $79.95) is faster but also suffers from a difficult installation. The manual says in one place that the program will disable SMARTDRV, but it doesn't Its driver must install after the CD-ROM device driver, but the installation program doesn't necessarily put it there. It took three tries to get this one running, but when it runs, it earns its name. Lightning CD comes with keyboard and video speed enhancers and a directory tree deletion tool.

Norton Speedrive 4.0 (Symantec, 800-441-7234 or 408-252-3570, $99) is similarly fast. Its installation was the simplest, but it also required a manual tweak to the AUTOEXEC.BAT file that wasn't obvious untif my hard drive started locking up occasionally. It adds a couple of handy Windows applets to monitor and test cache performance. Eyecause of its safer installation routine, I would recommend Norton Speedrive for those who dislike having to fuss with the system files.