.\"	$NetBSD: gus.4,v 1.13 2008/04/30 13:10:54 martin Exp $
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by John T. Kohl.
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.Dd June 22, 2005
.Dt GUS 4
.Os
.Sh NAME
.Nm gus
.Nd
Gravis UltraSound/UltraSound MAX audio device driver
.Sh SYNOPSIS
.Cd "gus0 at isa? port 0xPPP irq X drq Y drq2 Z"
.Cd "audio* at audiobus?"
.Sh DESCRIPTION
The
.Nm
driver provides support for the Gravis UltraSound (GUS) and GUS MAX
audio cards.  Both cards have on-board memory which is used for
seamless playback of samples.  They can play back 8- or 16-bit samples
at up to 44.1kHz.  They can record 8-bit samples at up to 44.1kHz.
The UltraSound MAX is a full-duplex sound device, and if
configured with two DRQ channels can be used for simultaneous playback
and recording.  The I/O port base is jumper-selected, and may be chosen
from 0x210-0x260 in steps of 0x10.  (The normal setting is 0x220.)  The
GUS takes 16 ports at its base address and 8 ports at its base address +
0x100.
.Pp
The IRQ is software programmed, so you may select any IRQ from the set
{3,5,7,9,11,12,15}.  The DRQ lines are software programmed, and may be
chosen from {1,3,5,6,7}.  The drq2 field in the configuration file line
specifies a second DRQ line for recording.  If there is no drq2 field
in the config file, the playback channel will be used for recording DMA
and only half-duplex mode will be available.
.Pp
The Gravis UltraSound MAX has an additional CODEC onboard which is
addressed with four ports at an offset of 0x10C from the base ports
(0x31C-0x36C).
.Sh SEE ALSO
.Xr audio 4
.Sh REFERENCES
Gravis UltraSound Low-Level Toolkit, Revision 2.01, 20 May 1993,
published by Advanced Gravis and Forte Technologies.
.Sh HISTORY
The
.Nm gus
device driver appeared in
.Nx 1.1 .
.Sh BUGS
The full-duplex features of the GUS MAX have not been fully tested, and
full-duplex on the original GUS may not be possible at all.
.Pp
Only two voices on the GF1 synthesizer chip are used by this driver (for
left and right channels).
.Pp
Manipulating the mixer while audio samples are playing can lead to
device driver confusion (and maybe even a system panic).
.Pp
Manipulating the mixer device seems to create pregnant system pauses,
probably due to excessive interrupt masking.
.Pp
The joystick and MIDI port interfaces are not supported.