Technology and retro computer blog

Altair 8800 with FDC+ and 5.25" TEAC 55GFR dual drives

A project that I've wanted to do for a while is to set up the Altair with dual disk drives using the FDC+.  A few weeks back I managed to get hold of another TEAC 55 GFR drive thanks to a contact on the VCF.  So I finally got around to configuring both drives to work with the FDC+.  The new drive is a TEAC 55 GFR 612-U, it's a slightly different model to the other drive that I use which is a TEAC 55 GFR 149-U.  The 612-U has different jumpers to the 149-U but I managed to configure it close enough and it works fine with the Altair.

To hold the disk drives together I'm using a 5.25" drive rack that I cut out of an old pc.  I'm also using an AT power supply from the same pc to power the drives. 

Two TEAC 55 GFR floppy drives

Jumpers set on the TEAC GFR 612-U, drive set to D0 (disk 0)

Jumper settings on the TEAC GFR 149-U, drive set to D1 (disk 1)

The dual drive unit assembled and connected to the Altair

The Atlair running 63k CP/M with directory listings from both drives A and B

Running Ladder game under CP/M

Comments (2) -

  • Laurie

    16/02/2016 9:20:37 PM |

    Looks great.  Can you provide details of the cable conversion from 50 pin to 34 pin ?
    The photo suggests a brilliant little converter dongle but I cannot make out any more detail.  Greetings from the Blue Mountains NSW.  Laurie

    • tkc8800

      16/02/2016 11:54:26 PM |

      Hi Laurie,
      The small converter board has two connectors on it a 50 pin IDC and a 34 pin IDC.  The board itself simply has trace connections between the two connectors.  There a several adapter boards that come supplied with the FDC+ disk controller.  You select the adapter based on the type of floppy drive you want to use.  In my case because I'm using the TEAC 5.25" drives I created the 50 pin to 34 pin adapter.  The 34 pin cable is a standard PC floppy drive cable with 5.25" connectors.  The 50 pin cable is just a straight through 50 pin IDC cable.  More info can be found on the FDC+ at it's website here:

      Great to see another Aussie interested in the Altair!

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