• Please review our updated Terms and Rules here

Search results

  1. cr1901

    ATD M117 Reverse Engineering + Switch Settings

    I have an ATD Model M117 memory expansion board that came with my IBM 5150 when I got it in 2011. For the past several- 8, 9?- years, the card has not worked. I couldn't figure out whether it was because my DRAM was bad, I wasn't populating the DRAM banks correctly, I didn't have the correct...
  2. cr1901

    The move is complete, but the tweaking has only just begun

    Thank you to @modem7 for pointing this out, but there is a conversion from old posts to new. Using his example:
  3. cr1901

    The move is complete, but the tweaking has only just begun

    If still I get a "The old forum is currently down for an upgrade to Xenforo." landing page for a specific forum thread, does that mean the thread was lost completely, or just that that particular thread wasn't migrated yet? Relevant thread...
  4. cr1901

    Fixing bad sectors caused by a crash during hard drive write

    Ultimately, I ended up doing a reinstall. I used SpeedStor from modem7's site to low-level format the drive, and then run a surface analysis. I then compared the surface analysis to that of the IBM PC AT Advanced Diagnostics diskette. Both programs show the same three bad tracks (I couldn't...
  5. cr1901

    Fixing bad sectors caused by a crash during hard drive write

    Problem Statement Yesterday, I ran CHECKIT on my PC AT hard disk1 running DOS 5.0 and got a pleasant surprise: === HARD DISK 0 (C:) === Test Configuration: Cylinders: 614 Heads: 4 Sectors: 17 Capacity: 21,377,024 Bytes Test Results: Controller Diagnostic...
  6. cr1901

    1.44 Floppies with 82077AA

    Tonight, a friend showed me some information about the AT, PS/2-compatible 82077AA floppy disk controller. After reading over parts of the data sheet, I'm a bit confused and maybe someone who has access to one could run a test: Does the 82077AA support 1.44 MB 3.5" floppy disks for reading and...
  7. cr1901

    Run Time Error R6001 when running DOSSHELL

    This is a low-priority issue for me, since I don't normally run DOSSHELL, but it worries me all the same. Upon running DOSSHELL on my 1984 PC AT running IBM DOS 5, I get the following error after all directories are loaded: According to this Microsoft KB article, this error occurs when "The...
  8. cr1901

    Adlib Reproduction PCB

    http://tubetime.us/?p=419 https://github.com/schlae/adlib/tree/master This is excellent! I really want to make my own when I have some time/money. Apparently it's based somewhat off a design Sergey made.
  9. cr1901

    IBM System 34 Track Format Variations

    IBM 3740 Track Format is the soft-sectored FM format used by Shugart SA-800 drives and descendants. An overview of the format can be found in this document from Shugart, starting on PDF page 11. In order for a controller to figure out where the floppy is relative to a full rotation of the disc...
  10. cr1901

    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...
  11. cr1901

    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...
  12. cr1901

    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...
  13. cr1901

    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...
  14. cr1901

    MathJax CDN Support

    I wish to write a blog post that requires some math. It would be inconvenient for me to paste images each time I need to create a math equation, and so I wonder how difficult it would be to add MathJax support to the forum? Understandably so, this forum doesn't let you inject custom HTML, so I...
  15. cr1901

    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 :D! And there's a copious amount of documentation that I didn't know existed! I am going to focus...
  16. cr1901

    Shugart SA800 Theory of Operations question

    I offered to write a technical document on floppy drive theory of operation for preservation purposes. As part of my documentation, I wish to include circuit models for the R/W head as it is passed through various amplifiers and filters. I chose to discuss the Shugart SA800 because there exists...
  17. cr1901

    Demo of digitized audio through PC speaker

  18. cr1901

    Lisp 1.5 COND Multiple Expressions?

    Anybody here remember Lisp 1.5, specifically remember how to program using it? I know it's quite a ways back, but I've been studying it... possibly even thinking about implementing my own. Modern Lisps such as Scheme allow COND to have multiple statements to evaluate after each condition; this...
  19. cr1901

    8088 Assembly Variable/Scope management

    Note: Although I am focusing on 8088 code, any address-space-constrained arch qualifies here. Once again, I'm trying to write 8088 code- a text editor for fun- and not having much luck, even after creating a bunch of macros to help me manage variables. What do I mean by variable management...
  20. cr1901

    TSR techniques to save space

    Let's be honest: In DOS, every byte actually matters. This is especially apparent when it comes to TSRs! For those around during the era, what programming techniques/special assembler directives (creative uses of ORG?) did you use to code your TSRs to save space? In particular, here's one I've...