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cr1901

  1. RetroChallenge Jan 2016: What's Next?

    Although I was able to collect data from a floppy drive via FPGA, I don't have a working prototype yet. The next steps include:
    • Discussing clock and data windows
    • Discussing IBM track format
    • Creating the front end of a floppy controller exposed to a programmer
    • Publish my IPython notebooks consisting of data capture and building each FPGA component in a Python-to-Verilog library
    • Deployment and testing on real floppies
    • More pretty pictures.


    A write-enabled controller ...
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  2. RetroChallenge Jan 2016: MFM Primer (Alt: It's Like the Option Board, Except Not)

    Despite amazing progress last week, real life continues to be in the way. I need to work on time management skills in order to get more things done in a timely manner.

    Last week, I created a circuit on a breadboard attached to Mercury, a breadboard-friendly FPGA dev board. The resulting contraption is a little... less neat than I would like it to look, not to mention that I don't have the proper TTL parts ad mentioned in the previous entry. I'm in the process of making a floppy breakout ...

    Updated January 28th, 2016 at 03:29 PM by cr1901

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    RetroChallenge Jan 2016
  3. RetroChallenge Jan 2016: Not Quite According To Plan, But Progress Anyway.

    Hey, it's been two weeks w/o a post! Need to make sure I don't do that again.

    Real life's been busy; lately I've been reading Phase-Locked Loop literature (This book by Floyd Gardner is especially informative if you've had control theory), and figuring out how to convert the analog PLL on my IBM PC Floppy Disk Controller card to the digital domain (see last page of PDF). I've spent part of today hooking up my 5.25" floppy drive today to an FPGA logic analyzer that I synthesized... ...

    Updated January 19th, 2016 at 09:11 PM by cr1901

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    RetroChallenge Jan 2016
  4. RetroChallenge Jan 2016: Qualitative Floppy Disk Analysis

    Floppy Disk Operation Quick Reference
    Something I should have went over last post were quick fundamentals of floppy disk operation: A floppy disk stores information in the form of magnetic flux transitions. Flux transitions occur when the magnetic field on a floppy surface changes in strength. A circuit known as a Read/Write head creates a voltage from sensing a change in flux. This voltage is maximized at the boundaries where the magnetic field completely changes polarity/direction. The ...

    Updated January 30th, 2016 at 01:05 PM by cr1901

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    RetroChallenge Jan 2016
  5. Retrochallenge 2016 Introduction

    My first Retrochallenge... I've been meaning to figure out how floppy disks store data down to the magnetic transition level for some time. This gives me an excuse to learn and document my findings ! And there's a copious amount of documentation that I didn't know existed!

    I am going to focus on documenting my findings for IBM PC-compatible DD 5.25" disks. These are the disk types where I understand the internals the best, even more so than 3.5" disks (which were still ...

    Updated December 31st, 2015 at 03:29 AM by cr1901

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    RetroChallenge Jan 2016
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