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    I've just been around a long time--and my knowledge is pretty specialized. I know nothing of games or Apple boxes, for example--so I stay out of those conversations.
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    I can neither confirm nor deny.
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About cr1901

Basic Information

Date of Birth
May 29, 1990 (30)
About cr1901
I take a lot of slack for my vintage computing hobby from my peers at school- they just don't get it lol!

When applicable: My lack of recent posts does not imply that I'm no longer interested in the hobby. It simply implies a lack of money to spend :P.

My posting rate is extremely sporadic as well. As an example... before June 2013, it had been months since I made any real number of posts... it is now August 2013, and I've made more posts in the past 2 months than I have since I joined the forums in 2011. Granted, most of these posts were in two threads, but still. The interest never goes away completely.

Not too interested in vintage games (well, in the PC world anyway- SNES and Genesis are a different story!), but I do take an interest in Hercules-compatibility and also have a fondness for maze games (of all things!).
Repairing vintage items, electronics, programming, and spending time with friends.
Electrical Computer Engineering Graduate Student


Looking for: Needham's Electronics PB-10 Microcontroller Adapter (looking for one since early 2012!).


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February 4th, 2013 06:33 PM
General Information
Last Activity
February 26th, 2021 06:47 PM
Join Date
December 28th, 2011
View cr1901's Blog

Recent Entries

RetroChallenge Jan 2016: What's Next?

by cr1901 on January 31st, 2016 at 04:20 PM
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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RetroChallenge Jan 2016: MFM Primer (Alt: It's Like the Option Board, Except Not)

by cr1901 on January 28th, 2016 at 09:58 AM
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

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Updated January 28th, 2016 at 04:29 PM by cr1901

RetroChallenge Jan 2016

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

by cr1901 on January 19th, 2016 at 10:04 PM
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...

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Updated January 19th, 2016 at 10:11 PM by cr1901

RetroChallenge Jan 2016

RetroChallenge Jan 2016: Qualitative Floppy Disk Analysis

by cr1901 on January 6th, 2016 at 02:41 PM
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

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Updated January 30th, 2016 at 02:05 PM by cr1901

RetroChallenge Jan 2016

Retrochallenge 2016 Introduction

by cr1901 on December 30th, 2015 at 09:00 PM
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

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Updated December 31st, 2015 at 04:29 AM by cr1901

RetroChallenge Jan 2016