Re: Todd's ELF-ish to get an FDC #Homebrew #microboards


Hi, Todd! I added a 50 pin connector to my board because I run Microdos with 8” drives. The original 3.5 inch drives rotated at 600 rpm which gave the same data rate as an 8” drive. I have an original Sony 600 rpm 3.5” drive but I could never get it to run properly. I suspect it needs a major recalibration. Which led me to the Gotek floppy emulators. If you flash them with the HxC firmware you can recreate almost any drive ever made. I set mine up for 600 rpm, 500000 bit rate and loaded Dave’s Microdos image file. It worked perfectly. I then attached an 8 inch drive as Drive 1 and used Format and Sysgen to transfer the operating system to an 8 inch disk. 

Thanks for letting me know the changes you have made to the schematics. My board is designed to plug into the 44 pin RCA bus and I was surprised at how short most of the connections are. It never hurts to buffer though.

I’m not sure the Gotek drives actually have a model number. Mine just say Gotek. They are really cheap on Ebay and are usually designated for use with various musical instruments. The secret is to give them the HxC firmware which can be purchased here:
When used with the HxC floppy emulator software almost any drive ever made, if not every drive ever made, can be reproduced. I have used them with several CP/M machines and they can be lifesavers.

On Feb 21, 2020, at 5:12 PM, taf123 <todd.ferguson@...> wrote:

Hi again Cellarcat!

Bummer about the 18S651 - I was happy to hear that you had gotten that going.  Be interested if you can track it down.  By the way, what's the model numbers of those floppy emulators you have in that pic?

Nice spot on the schematic. I did the exact same thing with INDCL on pin 4 of U14A to pin 5 of U7B.  Funnily enough, my pattern matching didn't even notice while building and I wired it correctly ;-)


I made some changes/corrections compared to the schematic the is currently available. 
  • I buffered SC0 and SC1.  This required changing U4 to an 74HC244.  Across the complete ELF-ish, those lines travel quite a ways without any buffering.  Your mileage may vary.
  • Added pull-up resistors to U24 MOTON0-4 lines
  • The !CLR pins (P2) on U21 and U22 should be driven by !CLEAR instead of CLEAR - oops.
    • Decided to buffer !CLEAR as well
  • Added a jumper block to set all four drive motors always on.
  • Changed the drive of LCT from U12D to U16B so it wouldn't have to be such a long wire run there and back.
  • In the picture, you can see I have an additional power distribution point in the upper half of the board, just under the 34-pin connectors, and I decided to add a 10uF tan there.  This is C2 on page 1.

There could be other minor changes.

Not knowing anyone was following along, I hadn't uploaded the changed.  Now I have, as ELF-BB-FDC-II_20200221.pdf.

Best regards,

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