TI-99/4A FAQ: Disk Drives

Using Disk Drives on a TI-99/4a

Disk drives on the TI are used similar to other storage and output devices. They are addressed like any other device by their device name.

The 3 drives supported with the Texas Instruments disk controller are

  • DEVICE NAME   –   disk drive number
  • DSK1.                   –  Drive 1
  • DSK2.                   –  Drive 2
  • DSK3.                   –  Drive 3

Other 3rd party controllers supported an additional DSK4.  device – Drive 4.

To access devices in basic, you use these commands.

    • Example:  OLD DSK1.FILENAME would load a file named FILENAME off DSK1.
    • Example: SAVE DSK1.FILENAME would save a file named FILENAME on DSK1.

REMINDER: all DEVICE NAMES ARE IN UPPERCASE, make sure you are using uppercase, you can easily assume the lowercase font is upper case as it looks simular to the upper case font (just smaller) so be sure ..  filenames can be case sensitive so I find it’s best to make them all uppercase as well.

See also: https://www.arcadeshopper.com/wp/ti-99-4a-faq-loading-assembly-language-programs/

Disk formatting

Disks on the TI use a proprietary format that is unreadable by other computer systems without special tools. For more information on disk formats check out this page.  https://www.arcadeshopper.com/wp/ti-99-4a-faq-floppy-disk-drives-and-formats/

To format a disk on your TI you need a DISK MANAGER program. This contains the software to format new disks, copy files, make backups etc.  There are 3 versions of disk manager from Texas Instruments and many 3rd party/shareware disk managers.

Texas Instruments Disk managers:

  • Disk Manager – Formats SS/SD disks
  • Disk Manager 2 – Formats SS/SD and DS/SD disks
  • Disk Manager 3 (rare) – Formats SS/SD, DS/SD, SS/DD and DS/DD disks.

The best disk manager currently available (in my opinion) is Disk Manager 2000 from Fred Kaal. It is available at his website here: https://www.ti99-geek.nl/  under projects and DM2K.

Common Drive issues

Floppy disks and drives are all very old at this point and are experiencing failures related to old capacitors,  broken/burned out optical sensors and LEDs etc.

Troubleshooting steps:

  • clean the drive heads, rails and lubricate with white lithium grease
  • inspect drive for broken parts or burned out LEDS
  • replace the cable with a new one, NO TWISTS

Drive options

TI made a stand alone disk controller and a PEB card that supported up to DS/SD diskettes. There is an 80 track modification available from hummingbird eproms to add 80 track drives to this controller.

Corcomp made a PEB disk controller and a sidecar “9900 Micro” that supported up to DS/DD diskettes.  http://mainbyte.com/ti99/hardware/9900_micro/9900_micro.html

Myarc made a PEB disk controller that supported up to DS/DD diskettes.

Myarc also made a HFDC (hard, floppy disk controller) for the PEB that will support up to 80 track DS/DD disks on a 4/a and fully format 1.44mb HD disks on a Geneve (with the appropriate drive).

Drive Emulation

You can hook up a GOTEK drive emulator with 3rd party firmware (I recommend flashfloppy.com) and use it as a SS/SD-DS/DD 5.25″ drive 40 or 80 track, DS/DD and DS/DD 3.5″ drive 40 or 80 track. Obviously you need a disk controller that supports the format you are trying to use.  Flashfloppy will use v9t9 format disk images as well as HXC format.

The Lotherek HXC also works well, however it is more expensive and less feature rich than the GOTEK.  To use this you must convert all your disk images to their HXC format. https://lotharek.pl/

TIPI provides drive emulation for level 1 and level 2 access through the map function. Allowing you to point DSK1. DSK2. DSK3. and/or DSK4. to whatever folder you want on the TIPI. drive. DSK0. always points to the root of the drive.






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