Making sense of the all-important X factor

All drives are rated in a reading and writing categories with an X number. Basically, the X means a multiple of the original speed of the specification. Thus, a CD-ROM drive that reads at 52X reads CDs 52 times faster than the original CD-ROM specification. On combo drives, you'll find a whole slew of X ratings: reading DVDs, writing DVDs, reading CDs, writing CDs, re-writing media, and so on.

In general, you want to look for high X ratings for every category.

Getting the lowdown on seek, access, and transfer rates

You'll encounter specifications called random seek time, random access time, sustained transfer rate, and burst rate. Here's what these mean:

• Random seek time: This represents the time it takes for the laser head to find the data requested. Typically, seek times run between 100 and 180 milliseconds depending on the format of the optical disk. The lower the time, the better.
• Random access time: Seek time is a component of access time. It indicates the time from the instruction to find data to when the data are actually starting to be read. It can run from 100 to 200 milliseconds.
• Sustained transfer rate: This indicates how fast the drive can transfer data at a sustained rate. Rates vary widely by the format, anywhere from around 2,500 kilobits per second (Kbps) to over 20,000 Kbps. The faster the better.
• Burst rate: This is how fast the drive can transfer data at its absolute, nonsustainable peak. UltraDMA (which most common ATAPI optical drives support) bursts at 33.3 megabits per second (Mbps).

Understanding optical drive formats

All optical drives can read some sort of media. Good old-fashioned CD-ROM drives can read CD-ROMs and music CDs. DVD-ROM drives can read CDs, CD-ROMs, DVDs, and DVD-ROMs.
Burners can write to various media. CD-RW drives can write music CDs and CD-ROMs. Recordable DVD drives of all types can record both of the DVD recordable formats, and to CD-RW. So if you have a DVD burner, you automatically have a CD-RW burner as well. Combination drives now exist that write to both of the major DVD recordable formats, DVD-RW and DVD+RW. Drives that can record to dual-layer media can record to all the lesser formats.

Besides reading and writing, most burners can rewrite. Using rewritable media, burners can write and overwrite the same disks. For example, CD-R (the R standing for recordable) discs can only be written to once, while CD-RW (Rewritable) disks can be written and overwritten. The same goes for DVD media: DVD-Rs can be written once, while DVD-RWs can be written to hundreds of times. Note that, for deleting files on an RW disk, you may need third-party software, as Windows XP often has trouble with that procedure.

When new technologies burst forth onto the market, semiconductor companies scramble to create standards to corner the market. Users end up being forced to gamble on which standard will catch on. Betamax owners found themselves out of luck when VHS took over the world. Some MiniDiscs never quite put a dent into the monolithic rise of audio CDs. Digital cameras are subject to a ridiculous array of memory cards and sticks, all of which are vying for dominance.

The writable CD format is pretty straightforward: You never have to worry about whether your CD burner will support a given format. Writable DVDs, however, are in a state of flux. Various companies jumped to create standards, and thus DVD-RAM, DVD-R or DVD-RW (pronounced DVD dash R or DVD dash RW), and DVD+R or DVD+RW (pronounced DVD plus R or DVD plus RW) all want superiority.
A lot of parity exists among the standards. They all hold a maximum capacity of 4.7GB (whereas CD-R or CD-RWs hold around 650MB). DVD-R and DVD+R are ideal for creating video DVDs as well as data DVDs. Which standard to use is up in the air; both claim superiority, both are better than DVD-RAM (not recommend), and neither differs much from the other.

There's more! DVD+RW DL drives are flooding the market, and DVD-RW DL drives aren't far behind. The DL stands for dual layer, indicating that the drives can write first to a shallow layer and then refocus the laser and write to a second layer, greatly increasing the storage capacity. A dual-layer disc can hold 8.5GB of data. To get the full benefit, you'll need expensive dual-layer discs to go with your dual-layer burner.
And speaking of media, you'll find a ton: Besides DVD+RW DL, you'll find DVD-R, DVD+R, DVD-RW, DVD+RW, and DVD-RAM. You'll even find the media rated for different speeds, in X ratings.