Zurich signal processing technology in IBM's 1 GB microdrive

The read channel containing NPML
technology is implemented on a
3 mm × 3 mm chip on the back of
the microdrive. Zurich, Switzerland, July 2000—Performance of the world's smallest hard disk drive, IBM's microdrive that now carries up to 1 GB of data on a disk 2.7 cm in diameter, relies to a considerable extent on a Zurich contribution: noise-predictive maximum-likelihood (NPML) detection for reliable recovery of data from readback signals.

IBM's new 1 GB microdrive can hold up to 1,000 high-resolution photographs, a thousand 200-page novels, or nearly 18 hours of high-quality digital audio music on a storage unit that is smaller than a matchbox. One of the critical technologies for such high density on a magnetic disk drive is the high-frequency read channel chip that reliably recovers the digital data from the analog readback signal. The 1 GB microdrive features a new detection and coding scheme that delivers significant performance gains over first-generation microdrives. Generally, the NPML technology developed at Zurich makes it possible for the storage density to be increased by some 30% compared to that of a hard disk that does not make use of this sophisticated signal-processing technology.