Derived from the recordable Minidisc, the MD-Data is the computer version of the disc Sony designed to replace the audio cassette. On a 64 mm cartridge magneto-optical disc, 140 megabytes can be stored on a sole operating side. Majors defaults of the MD-Data are its transfert rate which is only about 150 kilobyte/s (equal to the Compact Disc audio one), its data access time of 300 ms, and the price of recorders/readers. Aware of these flaws, Sharp considers nevertheless to give MD-Data a second chance, whereas Sony seems to have given up this product.
Sharp's MD-Data
reader/recorder
Sharp agreed with the american manufacturer National Semiconductor Corp. (Santa Clara, CA), who has developped a new controller/interface, which allows to minimize devices' costs, and make their integration in computers easier. Named MDIC for Multidrive Interface controller, this interface is held in one sole chip, and allows to connect directly a MD-Data recorder/reader to a 3.5'' magnetic floppy reader. The MDIC controller, along with a miniaturized optical head designed by Sharp, should allow Sharp to produce recorders/readers for PC and compatibles at best cost. The protoype presented at the Comdex'95 is 17mm high and takes the place of a magnetic floppy reader. It should be proposed to computer industrialists and PC manufacturers in December. First models will be available during first trimester 1996 at the average $200 OEM price. Mass production is planned for third trimester 1996, in case of demand.
Aware of the technical flaws of the primary MD-Data, Sharp considers designing double and quadruple speed recorders/readers, able to sustain a 300 or 600 megabyte/s rate (NoT : meant kilobyte/s), by speeding up the disc rotation. It will also propose to compress data before recording, in order to double the disc capacity, and bring it to 280 megabytes. As a second step, Sharp plans to quadruple MD-Data storage density, by modifying physical recording characteristics. Its engineers would have proved that it is possible to write data on tracks and between tracks, by changing wavelength and tracks width at once. This would bring the capacity to 700 megabytes "en natif" (i.e. without compression). They would use in this case a 680 nm wavelength against 780 nm today, pit size would then be reduce from 0.9 µm to 0.45 µm. Sharp's engineers designed too a specific MD-Data medium to answer the problems of this density increase. Its optical structure has two magneto-optical layers combined with a virtual mask mechanism, which eleminates interferences between the two zones. All this is still laboratory researching, which gave no commercial product yet. On the other hand Sharp will have to agree with Sony, which is at the start of the MiniDisc and the MD-Data.
Even if one cannot see what grounded this decision, Sharp seems to set its heart on the MD-Data as a backup and diffusion medium, complementary to the CD-ROM because erasable and recordable. Just like Sony one year ago, Sharp would like the MD-Data become the successor of the today magnetic floppy disk. Its leaders foresee also uses for the MD-Data and its future generations in PDAs, numeric cameras, etc. But here is still the most difficult : to convince today manufaturers and users, who were not yesterday, to this point of view.
Francis
Pelletier
© 1995 MOSARCA - All rights
reserved
