The Yamaha YMF7xx family of microchips is a series of audio controllers for use in personal computers. The last model number for controller chips used on ISA bus cards is 719; chips used on PCI cards start at 720 and higher. Chips for PCI bus standalone adapters are marked YMF7x4, while on-board or embedded solutions are marked YMF7x0. The YMF7x4 series features hardware-assisted XG MIDI synthesis with either 32- or 64-note polyphony, full-duplex playback and recording at any samplerate (internally upsampled to 48 kHz), external game controller and MIDI interface, and a legacy block for DOS application support.
YMF7xx chips were used in many inexpensive (sub-$50) soundcards. Relative performance was good despite the typical low cost. The cards were usually equipped with good quality 18-bit Digital-to-Analogue Converters, providing similar low noise and harmonic distortion levels to those found in semi-professional hardware.
The XG synthesizer on the YMF7x4 series features not only basic XG System Level 1, but also some of the MU-50 additions, and can reproduce most musical data previously programmed for the popular DB50XG daughterboard. YMF7x4 cards shipped with a 2 MB wavetable bank of 8-bit samples by default, which must be loaded into system RAM during booting. Neither the resolution nor content of the wavetable bank are hardware limitations. A user can load their own banks using third-party tools to further improve sound quality or completely change the set of instruments. As with most other XG standard tone generators, YMF7x4 can switch itself into TG300B mode, which is an emulation of the Roland GS standard that allows adequate playback of musical data bearing the GS logo.
Legacy support includes an OPL3 FM synthesizer, Sound Blaster Pro (22 kHz 8-bit Stereo) emulation and MPU-401 compatible MIDI interface. In addition to OPL3, DOS applications running under Windows 9x/Me can also use the XG tone generator.
All of these features are available using Yamaha's VxD driver under Windows 9x/Me. WDM drivers for these operating systems and later Windows 2000/XP provide subjectively unacceptable XG MIDI synthesis (General MIDI synthesis is considered acceptable), and may lack important mixer controls, like separate Line-Out and 3D Wide. Legacy mode is not supported under NT-based OSes.
The original version of the YMF7x4 chipset series is the YMF724. It is limited to two-channel output. It is followed by the YMF744 and its variants, which feature four-channel output. The final and most advanced version of the YMF7x4 chipset series is the YMF754, which also features standard four-channel output, but adds lower power consumption features. The most feature-rich soundcards based on the YMF754 are the Labway XWave 6000 (which has an additional hardware chip to emulate 5.1 surround sound and a six-channel amplifier providing 2W per channel) and the Hoontech SoundTrack i-Phone Digital XG (which features an additional connector for an included speech-optimized headset microphone as well as support circuitry that limits feedback in telephony applications).