You can read the timer's countdown counter instead of relying solely on the tick; it runs at 1.2 MHz approximately.
ms dos compatible != IBM PC compatible. 80186 based PC will still run TP programs, despite Timer0 being mapped to port 30-36H instead of 40-43H, not to mention totally non 8253 compatible.
I always assumed it was 16hz. Oh well. That was a long time ago.