Tandy 1000 SL Technical Reference Manual page 567

Software
This BIOS call uses the DMA hardware to input and output the
sound buffer. When functions AH
=
82H and AH
=
83H are
called, the BIOS initiates the 1/0 and returns to the calling
program immediately. When the DMA transfer is complete, the
BIOS will receive a hardware interrupt and will execute a
software INT 15H with AH
=
91H and AL
=
FBH. If an applica-
tion program needs to know when the data transfer is complete,
it has to hook INT 1 5 H and watch for this event.
The BIOS call masks the hardware restriction of not being able
to DMA across a 64 kilobyte memory address boundary from the
calling program.
46.