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HU430 NLX Motherboard User Guide
The video memory comprises 4 pieces of 256Kx16 40-pin SOJ to give a maximum of 2MB
(64-bits wide). Board builds populated with only 1MB (2 pieces) will have two sockets fitted
to enable the memory to be upgraded to 2MB. The memory type is 40ns EDO DRAM.
An AMC (ATI Media Connector) is also fitted; this is a 40-pin (extended) version of the 26-
way VESA feature connector.
2.6 Audio
The audio system is based on the Crystal CS4236B. It is a single chip audio controller
compatible with Sound Blaster, Sound Blaster Pro and the Windows Sound System.
Audio features:
Plug-and-Play ISA bus interface
16-bit address decode support
Internal FM Synthesis Support
Dual DMA Support w/FIFOs, full duplex operation
Programmable Power Management
Joystick Port and MPU-401 compatible MIDI interface
6 channel Input Mixer.
The audio circuit's output stage is a National Semiconductor LM4880 stereo power amplifier
(Boomer family). It drives a single mono internal speaker or a stereo headphone output jack.
The amplifier will produce 600 mW RMS for the internal speaker and approximately 65 mW
RMS per channel for stereo headphones (32
derived from the stereo output mixer of the audio controller and the internal speaker's signal
is derived from the audio controller's separate mono output stage. In the Windows mixer
panel, it is necessary to un-mute the 'PC Speaker' output as this controls the audio controller's
mono output.
A microphone input jack is provided with phantom power for electret condenser
microphones. An optional CD-ROM audio connector is provided for connecting the internal
CD-ROM drive's audio output into the motherboard sound system.
There is a 16-way header which provides the MIDI and joystick functionality via an optional-
fit 15-way D-type cable assembly.
The audio section can be completely de-populated, leaving the conventional PC-Beep. The
PC beep is always available from the small PCB-mounted speaker if the enable jumper is
present. The output of the audio sub-system is never fed to the PCB-mounted speaker.
If the audio sub-system is not fitted, then the PC beep signal is fed up the NLX riser on the
left channel. If the audio sub-system is fitted then the mono speaker output is fed up the NLX
riser on the left channel.
2.7 Standard I/O
The SMC FDC37C675 combo controller provides standard I/O. This comprises the four
functional blocks below. It is packaged in a 100-pin QFP and is fully PC97 and motherboard
Plug-and-Play compliant. It supports three ISA DMA channels and supports a serial interrupt
Mitsubishi Electric PC Division
impedance). The stereo headphone output is
124575UG Revision 2
Page 8 of 21
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