Namco 163

About

This chip was created by Namco and contains up to eight wave channels, this chip was earlier erroneously known as Namco 106 (which is the same chip but without the audio capabilities). It was used in multiple Namco games, such as Final Lap, King of Kings and Rolling Thunder.

The chip has 128 bytes of RAM for wave storage, but the last 64 bytes is shared with the audio registers so the wave area is practically limited to 64 bytes (or 128 wave steps). Each channel can use a wave size from 4 to 256 steps, but most NSF players supports only 32 steps as the largest size so this is the limitation in the tracker at the moment.

Note: This chip has 8 channels in total, but the actual number of channels to use is configurable (from the module properties dialog). This is an important feature because all channels are clocked sequentally by the chip, so the pitch range will depend on the channel count: a lower number of channels allows an extended top pitch range. More channels will also increase the effects of aliasing (since this chip uses a phase accumulator as frequency divider).

What is even more important is that the DAC is also shared by all channels in the same sequential manner. The rate for this channel switching is 120 kHz which means that when all 8 channels are enabled, there will be audible channel switching noise at 15 kHz (or 17 kHz when 7 channels are enabled) The Namco cart did not have a LP filter to deal with this, so it is very audible. To avoid this, do not use 8 (or 7) channels. This behaviour is not commonly emulated by NSF players (at the moment), with the exception of NEZplug++.

Instruments

Envelopes

Namco instruments has an envelope editor that behaves like 2A03, with the exception for an extra wave setting.

See 2A03 instruments for more information.

Wave

This tab is used to define waves for the instrument, the wave editor is the same as used for FDS except that only 16 levels are available and the wave size is customizable. Like for FDS, a few presets are available.

Up to 16 different waves can be stored in the same instrument, and the wave to actually use is controlled by the wave envelope setting or the V pattern effect. Only one wave is uploaded the the wave memory at the time.

The location in the wave memory is customizable, and the user is responsible for being sure that no instruments tries to use the same memory position simultaneously! For example, two instruments that uses wave position 0 cannot be used at the same time, but can be used at different times. Two instruments that uses wave position 0 and 32 can be used simultaneously.

The instrument editor will suggest wave positions depending on the wave size.

Also be aware that the pitch table is calculated with 32 steps waves in mind, so waves that are not a power of two in size will be out of tune.

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