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.

Loading files: OLD DEVICENAME.FILENAME
- Example: OLD DSK1.FILENAME would load a file named FILENAME off DSK1.
Saving files: SAVE DEVICENAME.FILENAME
- 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 Catalog

In TI Basic you can enter this program:

100 CALL CLEAR
110 COUNT=0
120 DIM TYPE$(6)
130 TYPE$(1)="DIS/FIX"
140 TYPE$(2)="DIS/VAR"
150 TYPE$(3)="INT/FIX"
160 TYPE$(4)="INT/VAR"
170 TYPE$(5)="PROGRAM"
175 TYPE$(6)=" <DIR> "
180 INPUT "DEVICE:":DEV$
190 IF SEG$(DEV$,LEN(DEV$),1)="." THEN 210
200 DEV$=DEV$&"."
210 REM  THIS OPENS AS IF/0 - WHICH BECOMES IF/38 
220 OPEN #1:DEV$,INPUT ,RELATIVE,INTERNAL
230 REM  'ZERO' IS ALWAYS 0 
240 INPUT #1:DISKNAME$,ZERO,DISKSECTORS,FREESECTORS
250 DISPLAY "DSK0 -  DISKNAME= ";DISKNAME$:"AVAILABLE= ";FREESECTORS;" USED= ";DISKSECTORS-FREESECTORS
260 DISPLAY :"FILENAME   SIZE    TYPE    P":"---------- ---- ---------- -";
270 REM  A FILETYPE OF 0 ALSO MEANS END OF DIRECTORY 
280 REM  FILETYPE IS NEGATIVE FOR A PROTECTED FILE 
290 INPUT #1:FILENAME$,FILETYPE,FILESECTORS,RECORDLENGTH
300 IF LEN(FILENAME$)=0 THEN 400
310 COUNT=COUNT+1
320 DISPLAY :COUNT;FILENAME$;TAB(12);FILESECTORS;TAB(17);TYPE$(ABS(FILETYPE));
330 REM  PROGRAM FILES DON'T HAVE A RECORD LENGTH 
340 IF ABS(FILETYPE)>=5 THEN 370
350 B$=" "&STR$(RECORDLENGTH)
360 DISPLAY SEG$(B$,LEN(B$)-2,3);
370 IF FILETYPE>0 THEN 290
380 DISPLAY TAB(28);"Y";
390 GOTO 290
400 CLOSE #1

Also you can get a catalog in a number of other ways.

Disk manager software
- TI’s Disk Manager, Disk manager 2 and Disk manager 3 will all produce catalogs of disks
- DM1000
- DM2000
- other disk manager programs
Extended Basic 2.7
- CALL CAT(“DSK1.”) will show a catalog of DSK1.
Miller’s graphics ROMs in a corcomp controller
- CALL CAT(“DSK1.”) will show a catalog of DSK1.

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.