TrueX is a technology used in some CD-ROM drives that greatly increases the drives performance, while reducing CPU utilization dramatically.
TrueX was developed as a way to increase the transfer rate of a CD-ROM drive without further increasing the spin rate of the disc. You see drives with very high spin rates suffer from vibration problems and long spin up times (not to mention high CPU utilization). A normal high spin rate CD-ROM drive (16X and up), usually only averages about 60 percent of its advertised transfer rate. This is due to vibration problems and the way data is recorded onto the discs themselves. TrueX drives on the other hand consistantly average higher transfer rates than their standard counterparts. These higher transfer rates apply over the entire disc, not just the data recorded on the outer portion (the data on the outer portion is the only a data that a normal drive can transfer at its advertised speed).
A normal 40X IDE CD-ROM drive will average a 3750 KB per second transfer rate, while using an average of 52 percent of the CPU's cycles, but these numbers vary wildly, it all depends on where the data is on the disc. While a 40X "TrueX" drive will average 6750 KB per second across the entire disc, while only using 18 percent of the CPU's cycles, regardless of where the data is recorded on the disc. The difference is like night and day. Please note that the CPU utilization totals were for a Pentium 3 at 500 Mhz, and your totals may vary.
I purchased a HiVal 40X "TrueX" drive when they first came out (back in 1999), and that thing was faster than my hard drive was back then. (I benchmarked both, and the CD-Rom drive beat my hard drive by a small margin in the benchmarks). Although hard drives have much lower seek times, so they are still better overall performers. In the few years since then cheap hard drives have sped up quite a bit, so you probably won't be able to get a "TrueX" drive that outperforms your hard drive anymore (unless you have an older system).
How does this amazing technology work, you may ask? It is a simple concept. A normal CD-ROM drive reads the disc with a single laser, while a "TrueX" drive splits the laser into seven parts, to read seven tracks at the same time. Twenty beam versions are said to be in development (those probably could give hard drives a run for their money again).
The technology itself was created by Zen Technologies. They do not make drives themselves, instead they license their technology to other drive makers. Kenwood is currently the largest manufacturer of these drives. They sell them under both the Kenwood and HiVal names. You can save money by purchasing the "HiVal" versions of these drives, as they are identical to the "Kenwood" ones in every way except for the faceplate.