MPU-401

Roland MPU-401 (top-cover removed).

The MPU-401, where MPU stands for MIDI Processing Unit, was an important but now obsolete interface for connecting MIDI-equipped electronic music hardware to personal computers. It was designed by Roland Corporation, which also co-authored the MIDI standard.

Design

Released around 1984, the original MPU-401 was an external breakout box providing MIDI IN/MIDI OUT/MIDI THRU/TAPE IN/TAPE OUT/MIDI SYNC connectors, for use with a separately-sold interface card/cartridge ("MPU-401 interface kit") inserted into a computer system. For this setup, the following "interface kits" were made:

In 2014 hobbyists built clones of the MIF-IPC-A card for PCs.[5]

Variants

Later, Roland would put most of the electronics originally found in the breakout box onto the interface card itself, thus reducing the size of the breakout box. Products released in this manner:

Still later, Roland would get rid of the breakout box completely and put all connectors on the back of the interface card itself. Products released in this manner:

Roland MPU-IPC, the rare 'Micro Channel' version of the card.
Roland MPU-401AT

Clones

By the late 1980s other manufacturers of PCBs developed intelligent MPU-401 clones. Some of these, like Voyetra, were equipped with Roland chips whereas others had retro-engineered ROMs (Midiman / Music Quest).[10][11]

Examples:

In 2015 hobbyists developed a Music Quest PC MIDI Card 8BIT clone.[14]

Modes

The MPU-401 can work in two modes, normal mode and UART mode. "Normal mode" would provide the host system with an 8-track sequencer, MIDI clock output, SYNC 24 signal output, Tape Sync and a metronome; as a result of these features, it is often called "intelligent mode". Compare this to UART mode, which reduces the MPU-401 to simply relaying in-/outcoming MIDI data bytes.

As computers became more powerful, the features offered in "intelligent mode" became obsolete, as implementing them in the host system's software became more efficient (than paying for dedicated hardware that will do them). As a result, the UART mode became the dominant mode of operation, with many clones not supporting the "intelligent mode" at all, being advertised as MPU-401 compatible.

SoftMPU

In the mid 2010s a hobbyist platform software interface, SoftMPU, was written that upgrades UART (non intelligent) MPU-401 interfaces to intelligent MPU-401 interface.[15]

In 2015 a PCB (HardMPU) was developed that incorporates SoftMPU as logic on hardware (so that the PC's CPU does not have to process intelligent MIDI). [16]

Contemporary interfaces

Physical MIDI connections are increasingly replaced with the USB interface, and a USB to MIDI converter in order to drive musical peripherals which do not yet have their own USB ports. Often, peripherals are able to accept MIDI input through USB and route it to the traditional DIN connectors. While MPU-401 support is no longer included in Windows Vista, a driver is available on Windows Update.[17] As of 2011 the interface is still supported by Linux and Mac OS X.

References

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