Path: utzoo!attcan!uunet!comp.vuw.ac.nz!waikato!hamish From: hamish@waikato.ac.nz Newsgroups: comp.sys.amiga.tech Subject: Re: Compression device Message-ID: <1997.271c5334@waikato.ac.nz> Date: 16 Oct 90 23:48:52 GMT References: <291@geocub.greco-prog.fr> <1990Oct15.120046.15007@ericsson.se> Organization: University of Waikato, Hamilton, New Zealand Lines: 46 In article , phil@adam.adelaide.edu.au (Phil Kernick) writes: > In article <291@geocub.greco-prog.fr> anthes@geocub.greco-prog.fr (Franklin Anthes) writes: > - > -I'd really like to find an amiga device (comp:?) which would automatically > -compress/decompress any files stored on it. I don't think such a device would > -be able to handle direct access ( it could probably fake it though ). But > -it still would be a really usefull tool. > > Isn't this basically how an RLL hard-drive controller on an I*M works? > As I understand it, it run-length encodes the data to be put on the > hard drive before storing it, and decodes it when reading it off. > > This would mean slightly slower access times, but an increase in disk > capacity of about 50%. > Not quite. RLL and MFM are just two different ways of encoding separate bits in a stream of them. The RLL gives higher densities, simply because it has a diffent number of transitions for a given bit pattern than MFM, and so can be recorded at a higher density. MFM is also an example of RLL encodeing, however the method is slightly different, and so the number of transitions written to the substrate is different. For a complete explanation see BYTE magazine. They had a piece on encoding bits on disk substrates not too long ago, however I can't remember the issue off hand. (any body?). > Phil. > -- > Phil Kernick EMail: phil@adam.adelaide.edu.au > Departmental Engineer Phone: +618 228 5914 > Dept. of Psychology Fax: +618 224 0464 > University of Adelaide Mail: GPO Box 498 Adelaide SA 5001 -- ============================================================================== | Hamish Marson | Internet hamish@waikato.ac.nz | | Computer Support Person | Phone (071)562889 xt 8181 | | Computer Science Department | Amiga 3000 for ME! | | University of Waikato | | ============================================================================== |Disclaimer: Anything said in this message is the personal opinion of the | | finger hitting the keyboard & doesn't represent my employers | | opinion in any way. (ie we probably don't agree) | ==============================================================================