This is a continuation of last month's article that dealt with the sound board, one of the two major pieces of computer hardware that is needed in a multimedia system.

The principal differences between various CD drives for personal computers are configuration, interface, CD insertion style, access speed, transfer rate, spindle speed and special features.

Configuration
If you have enough space (visible half-height 5 1/4" drive bay) inside your computer case, and your computer power supply is large enough and you don't need to share a CD drive between systems, the internal CD drive configuration is your best choice. External models have their own case and most have their own power supply which makes them generally more expensive than comparable internal models.

Interface
Most CD drives connect to your computer by either a SCSI or proprietary interface. Proprietary interfaces are unique to that particular CD drive manufacturer. Although this sounds bad, these drives come with their own interface card and are generally lower in cost than a comparable SCSI CD drive. If your sound card has a CD drive interface and you choose to use it, make sure that it is compatible with your CD drive! If you use a SCSI CD drive, be sure that you have any necessary software drivers and that your CD ROM drive is supported by your SCSI interface card.

CD insertion style
CD drives are manufactured with an internal CD tray or else they require a special CD-ROM holder. With tray style drive, you release the tray, drop the CD into the tray and then close the tray. Some models have manual tray release, while others have a "power tray". "Holder style" models require that each CD be placed into a special CD container and this unit is inserted into the drive. In an office where a single CD is passed between machines on a frequent basis, using a holder style drives eliminates touching the CD and the holder doubles as a protective case. If you have a large collection of CD titles, the cost of the holders can become an important and expensive issue.

Access Speed
All you really need to know is the smaller the access speed, the better. FYI: Average access speed is equal to the number of milliseconds (ms) that the CD drive can perform a 1/3 stroke on a 12 centimeter disk.

Transfer Rate / Spindle speed
Transfer rate and spindle speed are directly related. The transfer rate of most CD drive is approximately 150 Kbytes per second for single speed drives, 300 Kbytes per second for double speed drives and 450 Kbytes per second for triple speed drives. Data and program file access is improved with a double or triple speed drive, but standard audio CDs need to be played at single speed and the double or triple speed drive slows down. Triple CD drives are not as commonly available as either single or double speed drives and fetch a premium price.

Special features
Most CD drives meet or exceed the High Sierra and ISO 9660 specifications, but many do not support multi-session PhotoCD. Be sure to get one that supports PhotoCD as it is not an expensive "feature". You can use a front panel headphone jack and volume control, if you don't have a sound card to order to use the CD drive as a conventional CD player. If you have a sound card and are going to play the CD audio output through it, make sure that the CD drive has a rear audio connector. Also make sure that you have the proper audio cable to connect the CD drive to the sound card, as each sound card and CD drive has a different style of connector.

Choosing the drive you want to buy is determined by deciding what you want to accomplish, what equipment you already have installed, how much you want to spend and by comparing the specifications for each drive in each category. You should be able to easily obtain a reasonably priced internal drive with a proprietary interface, a 250-350 millisecond access speed, tray loading, single speed, multi-session PhotoCD compatibility, a headphone jack with volume control and rear audio connector.

On the horizon, are CD drives using the IDE interface and having even faster access speeds and higher transfer rates. Be sure not to overbuy and get more drive than you need, as you will probably be buying a new one in a few years. A CD drive purchased only two years ago would not be able to read a PhotoCD and low cost drives had an access speed of about 600 milliseconds!

Copyright © 1994 Rick Smith All rights reserved.