This project will develop a 400 MB removable cartridge magnetic disk drive for use in all forms of computers. There is a strong market need for a product of this type, utilising the excellent, proven, high-technology performance of fixed magnetic disk drives in a system that allows the removal of a fast, cheap, capacious storage unit.
The area storage density that required to achieve this target of 400 MB capacity on a single 95 mm disk is 300 Mbit per square inch. This will necessitate the successful application to a removable system of two state-of-the-art technologies that are now starting to appear in conventional fixed magnetic disk drives:
- magneto-resistive (MR) heads: unlike conventional inductive heads these produce a readback signal that is insensitive to the linear speed of the disk, and to not degrade the writing process at the extremely fast data rates required for multimedia video applications.
- partial response maximum likelihood (PRML) data channels: the conventional peak detection method for manipulation of the readback signal uses analog processing, but for very high performance systems it is becoming apparent that digital techniques such as PRML can offer significant increases in storage density.
Both of these new technologies, along with several existing techniques, will need developing much further to accommodate the particular environmental, mechanical and ergonomic requirements of removability. In addition, other important issues to be tackled include:
- misalignment between written and readback data when cartridges are moved from drive to drive, yielding off-track errors and skew-induced signal degradation
- increased exposure of the sensitive head and disk to contaminants
- lifting of the heads onto and away from the disk, without degrading the extremely precise flying characteristics, to allow insertion and removal of the cartridge.
The partners have arranged alliances with suppliers of the key components and subsystems to ensure a joint, focused development activity to address these issues. In some cases, parallel plans of attack will be undertaken, to maximise the chance of success and minimise the time to market.
The final deliverable will be a drive that has been exhaustively tested, and, in comparison with existing solutions, will offer improvements in access time (<15 ms), transfer rate (<10Mbyte/s), size (25 mm high) and price (average user cost >$0.6/Mbyte). It will also be marketed (with compression software) as the only drive allowing the user to copy a complete CD ROM onto a cartridge that can then run programs as fast as rigid drive.
CB4 4AE Cambridge
KY6 2DA Glenrothes