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MIDI | Electrical specifications | The MIDI 1.0 specification for the electrical interface is based on a fully isolated current loop. The MIDI out port nominally sources a +5 volt source through a 220 ohm resistor out through pin 4 on the MIDI out DIN connector, in on pin 4 of the receiving device's MIDI in DIN connector, through a 220 ohm protection resistor and the LED of an opto-isolator. The current then returns via pin 5 on the MIDI in port to the originating device's MIDI out port pin 5, again with a 220 ohm resistor in the path, giving a nominal current of about 5 milliamperes. | wiki:25699601 |
MIDI | Electrical specifications | Despite the cable's appearance, there is no conductive path between the two MIDI devices, only an optically isolated one. Properly designed MIDI devices are relatively immune to ground loops and similar interference. The data rate on this system is 31,250 bits per second, logic 0 being current on. The MIDI specification provides for a ground "wire" and a braid or foil shield, connected on pin 2, protecting the two signal-carrying conductors on pins 4 and 5. Although the MIDI cable is supposed to connect pin 2 and the braid or foil shield to chassis ground, it should do so only at the MIDI out port; the MIDI in port should leave pin 2 unconnected and isolated. | wiki:25699602 |
MIDI | Electrical specifications | Some large manufacturers of MIDI devices use modified MIDI in-only DIN 5-pin sockets with the metallic conductors intentionally omitted at pin positions 1, 2, and 3 so that the maximum voltage isolation is obtained. | wiki:25699603 |
MIDI | Extensions | MIDI's flexibility and widespread adoption have led to many refinements of the standard, and have enabled its application to purposes beyond those for which it was originally intended. | wiki:25699604 |
MIDI | General MIDI | MIDI allows selection of an instrument's sounds through program change messages, but there is no guarantee that any two instruments have the same sound at a given program location. Program #0 may be a piano on one instrument, or a flute on another. The General MIDI (GM) standard was established in 1991, and provides a standardized sound bank that allows a Standard MIDI File created on one device to sound similar when played back on another. GM specifies a bank of 128 sounds arranged into 16 families of eight related instruments, and assigns a specific program number to each instrument. | wiki:25699605 |
MIDI | General MIDI | Percussion instruments are placed on channel 10, and a specific MIDI note value is mapped to each percussion sound. GM-compliant devices must offer 24-note polyphony. Any given program change selects the same instrument sound on any GM-compatible instrument. General MIDI is defined by a standard layout of defined instrument sounds called 'patches', defined by a 'patch' number (program number – PC#) and triggered by pressing a key on a MIDI keyboard. This layout ensures MIDI sound modules and other MIDI devices faithfully reproduce the designated sounds expected by the user and maintains reliable and consistent sound palettes across different manufacturers MIDI devices. | wiki:25699606 |
MIDI | General MIDI | The GM standard eliminates variation in note mapping. Some manufacturers had disagreed over what note number should represent middle C, but GM specifies that note number 69 plays A440, which in turn fixes middle C as note number 60. GM-compatible devices are required to respond to velocity, aftertouch, and pitch bend, to be set to specified default values at startup, and to support certain controller numbers such as for sustain pedal, and Registered Parameter Numbers. A simplified version of GM, called "GM Lite", is used in mobile phones and other devices with limited processing power. | wiki:25699607 |
MIDI | GS, XG, and GM2 | A general opinion quickly formed that the GM's 128-instrument sound set was not large enough. Roland's General Standard, or GS, system included additional sounds, drumkits and effects, provided a "bank select" command that could be used to access them, and used MIDI Non-Registered Parameter Numbers (NRPNs) to access its new features. Yamaha's Extended General MIDI, or XG, followed in 1994. XG similarly offered extra sounds, drumkits and effects, but used standard controllers instead of NRPNs for editing, and increased polyphony to 32 voices. Both standards feature backward compatibility with the GM specification, but are not compatible with each other. Neither standard has been adopted beyond its creator, but both are commonly supported by music software titles. | wiki:25699608 |
MIDI | GS, XG, and GM2 | Member companies of Japan's AMEI developed the General MIDI Level 2 specification in 1999. GM2 maintains backward compatibility with GM, but increases polyphony to 32 voices, standardizes several controller numbers such as for sostenuto and soft pedal ("una corda"), RPNs and Universal System Exclusive Messages, and incorporates the MIDI Tuning Standard. GM2 is the basis of the instrument selection mechanism in Scalable Polyphony MIDI (SP-MIDI), a MIDI variant for low power devices that allows the device's polyphony to scale according to its processing power. | wiki:25699609 |
MIDI | Tuning standard | Most MIDI synthesizers use equal temperament tuning. The MIDI tuning standard (MTS), ratified in 1992, allows alternate tunings. MTS allows microtunings that can be loaded from a bank of up to 128 patches, and allows real-time adjustment of note pitches. Manufacturers are not required to support the standard. Those who do are not required to implement all of its features. | wiki:25699610 |
MIDI | Time code | A sequencer can drive a MIDI system with its internal clock, but when a system contains multiple sequencers, they must synchronize to a common clock. MIDI Time Code (MTC), developed by Digidesign, implements SysEx messages that have been developed specifically for timing purposes, and is able to translate to and from the SMPTE time code standard. MIDI Clock is based on tempo, but SMPTE time code is based on frames per second, and is independent of tempo. MTC, like SMPTE code, includes position information, and can adjust itself if a timing pulse is lost. MIDI interfaces such as Mark of the Unicorn's MIDI Timepiece can convert SMPTE code to MTC. | wiki:25699611 |
MIDI | Machine control | MIDI Machine Control (MMC) consists of a set of SysEx commands that operate the transport controls of hardware recording devices. MMC lets a sequencer send "Start", "Stop", and "Record" commands to a connected tape deck or hard disk recording system, and to fast-forward or rewind the device so that it starts playback at the same point as the sequencer. No synchronization data is involved, although the devices may synchronize through MTC. | wiki:25699612 |
MIDI | Show control | MIDI Show Control (MSC) is a set of SysEx commands for sequencing and remotely cueing show control devices such as lighting, music and sound playback, and motion control systems. Applications include stage productions, museum exhibits, recording studio control systems, and amusement park attractions. | wiki:25699613 |
MIDI | Timestamping | One solution to MIDI timing problems is to mark MIDI events with the times they are to be played, and store them in a buffer in the MIDI interface ahead of time. Sending data beforehand reduces the likelihood that a busy passage can send a large amount of information that overwhelms the transmission link. Once stored in the interface, the information is no longer subject to timing issues associated with USB jitter and computer operating system interrupts, and can be transmitted with a high degree of accuracy. MIDI timestamping only works when both hardware and software support it. MOTU's MTS, eMagic's AMT, and Steinberg's Midex 8 had implementations that were incompatible with each other, and required users to own software and hardware manufactured by the same company to work. | wiki:25699614 |
MIDI | Timestamping | Timestamping is built into FireWire MIDI interfaces, Mac OS X Core Audio, and Linux ALSA Sequencer. | wiki:25699615 |
MIDI | Sample dump standard | An unforeseen capability of SysEx messages was their use for transporting audio samples between instruments. This led to the development of the sample dump standard (SDS), which established a new SysEx format for sample transmission. The SDS was later augmented with a pair of commands that allow the transmission of information about sample loop points, without requiring that the entire sample be transmitted. | wiki:25699616 |
MIDI | Downloadable sounds | The Downloadable Sounds (DLS) specification, ratified in 1997, allows mobile devices and computer sound cards to expand their wave tables with downloadable sound sets. The DLS Level 2 Specification followed in 2006, and defined a standardized synthesizer architecture. The Mobile DLS standard calls for DLS banks to be combined with SP-MIDI, as self-contained Mobile XMF files. | wiki:25699617 |
MIDI | MIDI Polyphonic Expression | MIDI Polyphonic Expression (MPE) is a method of using MIDI that enables pitch bend, and other dimensions of expressive control, to be adjusted continuously for individual notes. MPE works by assigning each note to its own MIDI channel so that particular messages can be applied to each note individually. The specifications were released in November 2017 by AMEI and in January 2018 by the MMA. Instruments like the Continuum Fingerboard, Linnstrument, ROLI Seaboard, and Eigenharp let users control pitch, timbre, and other nuances for individual notes within chords. A growing number of soft synths and effects are also compatible with MPE (such as Equator, UVI Falcon, and Sandman Pro), as well as a few hardware synths (such as Modal Electronics 002 and ARGON8, Futuresonus Parva, and Modor NF-1). | wiki:25699618 |
MIDI | Alternative hardware transports | In addition to the original 31.25 kbit/s current-loop transported on 5-pin DIN, other connectors have been used for the same electrical data, and transmission of MIDI streams in different forms over USB, IEEE 1394 a.k.a. FireWire, and Ethernet is now common. Some samplers and hard drive recorders can also pass MIDI data between each other over SCSI. | wiki:25699619 |
MIDI | USB and FireWire | Members of the USB-IF in 1999 developed a standard for MIDI over USB, the "Universal Serial Bus Device Class Definition for MIDI Devices" MIDI over USB has become increasingly common as other interfaces that had been used for MIDI connections (serial, joystick, etc.) disappeared from personal computers. Linux, Microsoft Windows, Macintosh OS X, and Apple iOS operating systems include standard class drivers to support devices that use the "Universal Serial Bus Device Class Definition for MIDI Devices". Some manufacturers choose to implement a MIDI interface over USB that is designed to operate differently from the class specification, using custom drivers. | wiki:25699620 |
MIDI | USB and FireWire | Apple Computer developed the FireWire interface during the 1990s. It began to appear on digital video cameras toward the end of the decade, and on G3 Macintosh models in 1999. It was created for use with multimedia applications. Unlike USB, FireWire uses intelligent controllers that can manage their own transmission without attention from the main CPU. As with standard MIDI devices, FireWire devices can communicate with each other with no computer present. | wiki:25699621 |
MIDI | XLR connectors | The Octave-Plateau Voyetra-8 synthesizer was an early MIDI implementation using XLR3 connectors in place of the 5-pin DIN. It was released in the pre-MIDI years and later retrofitted with a MIDI interface but keeping its XLR connector. | wiki:25699622 |
MIDI | Serial parallel, and joystick port | As computer-based studio setups became common, MIDI devices that could connect directly to a computer became available. These typically used the 8-pin mini-DIN connector that was used by Apple for serial and printer ports prior to the introduction of the Blue & White G3 models. MIDI interfaces intended for use as the centerpiece of a studio, such as the Mark of the Unicorn MIDI Time Piece, were made possible by a "fast" transmission mode that could take advantage of these serial ports' ability to operate at 20 times the standard MIDI speed. Mini-DIN ports were built into some late-1990s MIDI instruments, and enabled such devices to be connected directly to a computer. | wiki:25699623 |
MIDI | Serial parallel, and joystick port | Some devices connected via PCs' DB-25 parallel port, or through the joystick port found in many PC sound cards. | wiki:25699624 |
MIDI | mLAN | Yamaha introduced the mLAN protocol in 1999. It was conceived as a Local Area Network for musical instruments using FireWire as the transport, and was designed to carry multiple MIDI channels together with multichannel digital audio, data file transfers, and time code. mLan was used in a number of Yamaha products, notably digital mixing consoles and the Motif synthesizer, and in third-party products such as the PreSonus FIREstation and the Korg Triton Studio. No new mLan products have been released since 2007. | wiki:25699625 |
MIDI | Ethernet and Internet | Computer network implementations of MIDI provide network routing capabilities, and the high-bandwidth channel that earlier alternatives to MIDI, such as ZIPI, were intended to bring. Proprietary implementations have existed since the 1980s, some of which use fiber optic cables for transmission. The Internet Engineering Task Force's RTP-MIDI open specification has gained industry support. Apple has supported this protocol from Mac OS X 10.4 onwards, and a Windows driver based on Apple's implementation exists for Windows XP and newer versions. | wiki:25699626 |
MIDI | Wireless | Systems for wireless MIDI transmission have been available since the 1980s. Several commercially available transmitters allow wireless transmission of MIDI and OSC signals over Wi-Fi and Bluetooth. iOS devices are able to function as MIDI control surfaces, using Wi-Fi and OSC. An XBee radio can be used to build a wireless MIDI transceiver as a do-it-yourself project. Android devices are able to function as full MIDI control surfaces using several different protocols over Wi-Fi and Bluetooth. | wiki:25699627 |
MIDI | TRS minijack | Some devices use standard 3.5 mm TRS audio minijack connectors for MIDI data, including the Korg Electribe 2 and the Arturia Beatstep Pro. Both come with adaptors that break out to standard 5-pin DIN connectors.. This became widespread enough that the Midi Manufacturers' Association standardized the wiring. The MIDI-over-minijack standards document also recommends the use of 2.5 mm connectors over 3.5 mm ones to avoid confusion with audio connectors. | wiki:25699628 |
MIDI | MIDI 2.0 | The MIDI 2.0 standard was presented on 17 January 2020 at the Winter NAMM Show in Anaheim, California at a session titled "Strategic Overview and Introduction to MIDI 2.0" by representatives Yamaha, Roli, Microsoft, Google, and the MIDI Association. This significant update adds bidirectional communication while maintaining backwards compatibility. The new protocol has been researched since 2005. Prototype devices have been shown privately at NAMM using wired and wireless connections and licensing and product certification policies have been developed, however no projected release date was announced. Proposed physical layer and transport layer included Ethernet-based protocols such as RTP MIDI and Audio Video Bridging/Time-Sensitive Networking, as well as User Datagram Protocol (UDP)-based transport . | wiki:25699629 |
MIDI | MIDI 2.0 | AMEI and MMA announced that complete specifications will be published following interoperability testing of prototype implementations from major manufacturers such as Google, Yamaha, Steinberg, Roland, Ableton, Native Instruments, and ROLI, among others. In January 2020, Roland announced the A-88mkII controller keyboard that supports MIDI 2.0. | wiki:25699630 |
MIDI | MIDI Capability Inquiry | MIDI Capability Inquiry (MIDI-CI) specifies Universal SysEx messages to implement device profiles, parameter exchange, and MIDI protocol negotiation. The specifications were released in November 2017 by AMEI and in January 2018 by the MMA. Parameter exchange defines methods to inquiry device capabilities, such as supported controllers, patch names, instrument profiles, device configuration and other metadata, and to get or set device configuration settings. Property exchange uses System Exclusive messages that carry JSON format data. Profiles define common sets of MIDI controllers for various instrument types, such as drawbar organs and analog synths, or for particular tasks, improving interoperability between instruments from different manufacturers. | wiki:25699631 |
MIDI | MIDI Capability Inquiry | Protocol negotiation allows devices to employ the Next Generation protocol or manufacturer-specific protocols. | wiki:25699632 |
MIDI | Universal MIDI Packet | MIDI 2.0 defines a new Universal MIDI Packet format, which contains messages of varying length (32, 64, 96 or 128 bits) depending on the payload type. This new packet format supports a total of 256 MIDI channels, organized in 16 groups of 16 channels; each group can carry either a MIDI 1.0 Protocol stream or new MIDI 2.0 Protocol stream, and can also include system messages, system exclusive data, and timestamps for precise rendering of several simultaneous notes. To simplify initial adoption, existing products are explicitly allowed to only implement MIDI 1.0 messages. The Universal MIDI Packet is intended for high-speed transport such as USB and Ethernet and is not supported on the existing 5-pin DIN connections. | wiki:25699633 |
MIDI | Universal MIDI Packet | System Real-Time and System Common messages are the same as defined in MIDI 1.0. | wiki:25699634 |
MIDI | New protocol | As of January 2019, the draft specification of the new protocol supports all core messages that also exist in MIDI 1.0, but extends their precision and resolution; it also defines many new high-precision controller messages. The specification defines default translation rules to convert between MIDI 2.0 Channel Voice and MIDI 1.0 Channel Voice messages that use different data resolution, as well as map 256 MIDI 2.0 streams to 16 MIDI 1.0 streams. | wiki:25699635 |
MIDI | Data transfer formats | System Exclusive 8 messages use a new 8-bit data format, based on Universal System Exclusive messages. Mixed Data Set messages are intended to transfer large sets of data. System Exclusive 7 messages use the previous 7-bit data format. | wiki:25699636 |
Microcode | Introduction | Microcode is a computer hardware technique that interposes a layer of organisation between the CPU hardware and the programmer-visible instruction set architecture of the computer. As such, the microcode is a layer of hardware-level instructions that implement higher-level machine code instructions or internal state machine sequencing in many digital processing elements. Microcode is used in general-purpose central processing units, although in current desktop CPUs, it is only a fallback path for cases that the faster hardwired control unit cannot handle. Microcode typically resides in special high-speed memory and translates machine instructions, state machine data or other input into sequences of detailed circuit-level operations. | wiki:25699637 |
Microcode | Introduction | It separates the machine instructions from the underlying electronics so that instructions can be designed and altered more freely. It also facilitates the building of complex multi-step instructions, while reducing the complexity of computer circuits. Writing microcode is often called microprogramming and the microcode in a particular processor implementation is sometimes called a microprogram. More extensive microcoding allows small and simple microarchitectures to emulate more powerful architectures with wider word length, more execution units and so on, which is a relatively simple way to achieve software compatibility between different products in a processor family. | wiki:25699638 |
Microcode | Overview | The lowest layer in a computer's software stack is traditionally raw binary machine code instructions for the processor. Microcode sits one level below this. To avoid confusion, each microprogram-related element is differentiated by the "micro" prefix: microinstruction, microassembler, microprogrammer, microarchitecture, etc. Engineers normally write the microcode during the design phase of a processor, storing it in a read-only memory (ROM) or programmable logic array (PLA) structure, or in a combination of both. However, machines also exist that have some or all microcode stored in SRAM or flash memory. This is traditionally denoted as "writeable control store" in the context of computers, which can be either read-only or read-write memory. | wiki:25699639 |
Microcode | Overview | In the latter case, the CPU initialization process loads microcode into the control store from another storage medium, with the possibility of altering the microcode to correct bugs in the instruction set, or to implement new machine instructions. Complex digital processors may also employ more than one (possibly microcode-based) control unit in order to delegate sub-tasks that must be performed essentially asynchronously in parallel. A high-level programmer, or even an assembly programmer, does not normally see or change microcode. Unlike machine code, which often retains some backward compatibility among different processors in a family, microcode only runs on the exact electronic circuitry for which it is designed, as it constitutes an inherent part of the particular processor design itself. | wiki:25699640 |
Microcode | Justification | Microcode was originally developed as a simpler method of developing the control logic for a computer. Initially, CPU instruction sets were hardwired. Each step needed to fetch, decode, and execute the machine instructions (including any operand address calculations, reads, and writes) was controlled directly by combinational logic and rather minimal sequential state machine circuitry. While such hard-wired processors were very efficient, the need for powerful instruction sets with multi-step addressing and complex operations ("see below") made them difficult to design and debug; highly encoded and varied-length instructions can contribute to this as well, especially when very irregular encodings are used. | wiki:25699641 |
Microcode | Justification | Microcode simplified the job by allowing much of the processor's behaviour and programming model to be defined via microprogram routines rather than by dedicated circuitry. Even late in the design process, microcode could easily be changed, whereas hard-wired CPU designs were very cumbersome to change. Thus, this greatly facilitated CPU design. From the 1940s to the late 1970s, a large portion of programming was done in assembly language; higher-level instructions mean greater programmer productivity, so an important advantage of microcode was the relative ease by which powerful machine instructions can be defined. The ultimate extension of this are "Directly Executable High Level Language" designs, in which each statement of a high-level language such as PL/I is entirely and directly executed by microcode, without compilation. | wiki:25699642 |
Microcode | Justification | The IBM Future Systems project and Data General Fountainhead Processor are examples of this. During the 1970s, CPU speeds grew more quickly than memory speeds and numerous techniques such as memory block transfer, memory pre-fetch and multi-level caches were used to alleviate this. High-level machine instructions, made possible by microcode, helped further, as fewer more complex machine instructions require less memory bandwidth. For example, an operation on a character string can be done as a single machine instruction, thus avoiding multiple instruction fetches. | wiki:25699643 |
Microcode | Benefits | A processor's microprograms operate on a more primitive, totally different, and much more hardware-oriented architecture than the assembly instructions visible to normal programmers. In coordination with the hardware, the microcode implements the programmer-visible architecture. The underlying hardware need not have a fixed relationship to the visible architecture. This makes it easier to implement a given instruction set architecture on a wide variety of underlying hardware micro-architectures. The IBM System/360 has a 32-bit architecture with 16 general-purpose registers, but most of the System/360 implementations actually use hardware that implemented a much simpler underlying microarchitecture; for example, the System/360 Model 30 has 8-bit data paths to the arithmetic logic unit (ALU) and main memory and implemented the general-purpose registers in a special unit of higher-speed core memory, and the System/360 Model 40 has 8-bit data paths to the ALU and 16-bit data paths to main memory and also implemented the general-purpose registers in a special unit of higher-speed core memory. | wiki:25699644 |
Microcode | Benefits | The Model 50 has full 32-bit data paths and implements the general-purpose registers in a special unit of higher-speed core memory. The Model 65 through the Model 195 have larger data paths and implement the general-purpose registers in faster transistor circuits. In this way, microprogramming enabled IBM to design many System/360 models with substantially different hardware and spanning a wide range of cost and performance, while making them all architecturally compatible. This dramatically reduces the number of unique system software programs that must be written for each model. A similar approach was used by Digital Equipment Corporation (DEC) in their VAX family of computers. | wiki:25699645 |
Microcode | Benefits | As a result, different VAX processors use different microarchitectures, yet the programmer-visible architecture does not change. | wiki:25699646 |
Microcode | History | In 1947, the design of the MIT Whirlwind introduced the concept of a control store as a way to simplify computer design and move beyond "ad hoc" methods. The control store is a diode matrix: a two-dimensional lattice, where one dimension accepts "control time pulses" from the CPU's internal clock, and the other connects to control signals on gates and other circuits. A "pulse distributor" takes the pulses generated by the CPU clock and breaks them up into eight separate time pulses, each of which activates a different row of the lattice. When the row is activated, it activates the control signals connected to it. | wiki:25699647 |
Microcode | History | Described another way, the signals transmitted by the control store are being played much like a player piano roll. That is, they are controlled by a sequence of very wide words constructed of bits, and they are "played" sequentially. In a control store, however, the "song" is short and repeated continuously. In 1951, Maurice Wilkes enhanced this concept by adding "conditional execution", a concept akin to a conditional in computer software. His initial implementation consisted of a pair of matrices: the first one generated signals in the manner of the Whirlwind control store, while the second matrix selected which row of signals (the microprogram instruction word, so to speak) to invoke on the next cycle. | wiki:25699648 |
Microcode | History | Conditionals were implemented by providing a way that a single line in the control store could choose from alternatives in the second matrix. This made the control signals conditional on the detected internal signal. Wilkes coined the term microprogramming to describe this feature and distinguish it from a simple control store. | wiki:25699649 |
Microcode | Implementation | Each microinstruction in a microprogram provides the bits that control the functional elements that internally compose a CPU. The advantage over a hard-wired CPU is that internal CPU control becomes a specialized form of a computer program. Microcode thus transforms a complex electronic design challenge (the control of a CPU) into a less complex programming challenge. To take advantage of this, a CPU is divided into several parts: There may also be a memory address register and a memory data register, used to access the main computer storage. Together, these elements form an "execution unit". Most modern CPUs have several execution units. | wiki:25699650 |
Microcode | Implementation | Even simple computers usually have one unit to read and write memory, and another to execute user code. These elements could often be brought together as a single chip. This chip comes in a fixed width that would form a "slice" through the execution unit. These are known as "bit slice" chips. The AMD Am2900 family is one of the best known examples of bit slice elements. The parts of the execution units and the execution units themselves are interconnected by a bundle of wires called a bus. Programmers develop microprograms, using basic software tools. A microassembler allows a programmer to define the table of bits symbolically. | wiki:25699651 |
Microcode | Implementation | Because of its close relationship to the underlying architecture, "microcode has several properties that make it difficult to generate using a compiler." A simulator program is intended to execute the bits in the same way as the electronics, and allows much more freedom to debug the microprogram. After the microprogram is finalized, and extensively tested, it is sometimes used as the input to a computer program that constructs logic to produce the same data. This program is similar to those used to optimize a programmable logic array. Even without fully optimal logic, heuristically optimized logic can vastly reduce the number of transistors from the number required for a ROM control store. | wiki:25699652 |
Microcode | Implementation | This reduces the cost of producing, and the electricity consumed by, a CPU. | wiki:25699653 |
Microcode | Horizontal microcode | "Horizontal microcode has several discrete micro-operations that are combined in a single microinstruction for simultaneous operation." Horizontal microcode is typically contained in a fairly wide control store; it is not uncommon for each word to be 108 bits or more. On each tick of a sequencer clock a microcode word is read, decoded, and used to control the functional elements that make up the CPU. In a typical implementation a horizontal microprogram word comprises fairly tightly defined groups of bits. For example, one simple arrangement might be: For this type of micromachine to implement a JUMP instruction with the address following the opcode, the microcode might require two clock ticks. | wiki:25699654 |
Microcode | Horizontal microcode | The engineer designing it would write microassembler source code looking something like this: For each tick it is common to find that only some portions of the CPU are used, with the remaining groups of bits in the microinstruction being no-ops. With careful design of hardware and microcode, this property can be exploited to parallelise operations that use different areas of the CPU; for example, in the case above, the ALU is not required during the first tick, so it could potentially be used to complete an earlier arithmetic instruction. | wiki:25699655 |
Microcode | Vertical microcode | In vertical microcode, each microinstruction is significantly encoded that is, the bit fields generally pass through intermediate combinatory logic that, in turn, generates the actual control and sequencing signals for internal CPU elements (ALU, registers, etc.). This is in contrast with horizontal microcode, in which the bit fields themselves either directly produce the control and sequencing signals or are only minimally encoded. Consequently, vertical microcode requires smaller instruction lengths and less storage, but requires more time to decode, resulting in a slower CPU clock. Some vertical microcode is just the assembly language of a simple conventional computer that is emulating a more complex computer. | wiki:25699656 |
Microcode | Vertical microcode | Some processors, such as DEC Alpha processors and the CMOS microprocessors on later IBM System/390 mainframes and z/Architecture mainframes, use machine code, running in a special mode that gives it access to special instructions, special registers, and other hardware resources not available to regular machine code, to implement some instructions and other functions, such as page table walks on Alpha processors. This is called PALcode on Alpha processors and millicode on IBM mainframe processors. Another form of vertical microcode has two fields: The "field select" selects which part of the CPU will be controlled by this word of the control store. | wiki:25699657 |
Microcode | Vertical microcode | The "field value" actually controls that part of the CPU. With this type of microcode, a designer explicitly chooses to make a slower CPU to save money by reducing the unused bits in the control store; however, the reduced complexity may increase the CPU's clock frequency, which lessens the effect of an increased number of cycles per instruction. | wiki:25699658 |
Microcode | Writable control store | A few computers were built using "writable microcode". In this design, rather than storing the microcode in ROM or hard-wired logic, the microcode is stored in a RAM called a "writable control store" or "WCS". Such a computer is sometimes called a "writable instruction set computer" or "WISC". Many experimental prototype computers use writable control stores; there are also commercial machines that use writable microcode, such as the Burroughs Small Systems, early Xerox workstations, the DEC VAX 8800 ("Nautilus") family, the Symbolics L- and G-machines, a number of IBM System/360 and System/370 implementations, some DEC PDP-10 machines, and the Data General Eclipse MV/8000. | wiki:25699659 |
Microcode | Writable control store | Many more machines offer user-programmable writable control stores as an option, including the HP 2100, DEC PDP-11/60 and Varian Data Machines V-70 series minicomputers. The IBM System/370 includes a facility called "Initial-Microprogram Load" ("IML" or "IMPL") that can be invoked from the console, as part of "power-on reset" ("POR") or from another processor in a tightly coupled multiprocessor complex. | wiki:25699660 |
Microcode | Comparison to VLIW and RISC | The design trend toward heavily microcoded processors with complex instructions began in the early 1960s and continued until roughly the mid-1980s. At that point the RISC design philosophy started becoming more prominent. A CPU that uses microcode generally takes several clock cycles to execute a single instruction, one clock cycle for each step in the microprogram for that instruction. Some CISC processors include instructions that can take a very long time to execute. Such variations interfere with both interrupt latency and, what is far more important in modern systems, pipelining. When designing a new processor, a hardwired control RISC has the following advantages over microcoded CISC: | wiki:25699661 |
Microcode | Micro Ops | Modern CISC implementations, such as the x86 family, decode instructions into dynamically buffered micro-operations ("μops") with an instruction encoding similar to RISC or traditional microcode. A hardwired instruction decode unit directly emits μops for common x86 instructions, but falls back to a more traditional microcode ROM for more complex or rarely used instructions. For example, an x86 might look up μops from microcode to handle complex multistep operations such as loop or string instructions, floating point unit transcendental functions or unusual values such as denormal numbers, and special purpose instructions such as CPUID. | wiki:25699662 |
Multitier architecture | Introduction | In software engineering, multitier architecture (often referred to as "n"-tier architecture) or multilayered architecture is a client–server architecture in which presentation, application processing and data management functions are physically separated. The most widespread use of multitier architecture is the three-tier architecture. "N"-tier application architecture provides a model by which developers can create flexible and reusable applications. By segregating an application into tiers, developers acquire the option of modifying or adding a specific layer, instead of reworking the entire application. A three-tier architecture is typically composed of a "presentation" tier, a "domain logic" tier, and a "data storage" tier. While the concepts of layer and tier are often used interchangeably, one fairly common point of view is that there is indeed a difference. | wiki:25699663 |
Multitier architecture | Introduction | This view holds that a "layer" is a logical structuring mechanism for the elements that make up the software solution, while a "tier" is a physical structuring mechanism for the system infrastructure. For example, a three-layer solution could easily be deployed on a single tier, such as a personal workstation. | wiki:25699664 |
Multitier architecture | Layers | The "Layers" architectural pattern has been described in various publications. | wiki:25699665 |
Multitier architecture | Common layers | In a logical multilayered architecture for an information system with an object-oriented design, the following four are the most common: The book "Domain Driven Design" describes some common uses for the above four layers, although its primary focus is the domain layer. If the application architecture has no explicit distinction between the business layer and the presentation layer (i.e., the presentation layer is considered part of the business layer), then a traditional client-server (two-tier) model has been implemented. | wiki:25699666 |
Multitier architecture | Three-tier architecture | Three-tier architecture is a client-server software architecture pattern in which the user interface (presentation), functional process logic ("business rules"), computer data storage and data access are developed and maintained as independent modules, most often on separate platforms. It was developed by John J. Donovan in Open Environment Corporation (OEC), a tools company he founded in Cambridge, Massachusetts. Apart from the usual advantages of modular software with well-defined interfaces, the three-tier architecture is intended to allow any of the three tiers to be upgraded or replaced independently in response to changes in requirements or technology. For example, a change of operating system in the "presentation tier" would only affect the user interface code. | wiki:25699667 |
Multitier architecture | Three-tier architecture | Typically, the user interface runs on a desktop PC or workstation and uses a standard graphical user interface, functional process logic that may consist of one or more separate modules running on a workstation or application server, and an RDBMS on a database server or mainframe that contains the computer data storage logic. The middle tier may be multitiered itself (in which case the overall architecture is called an ""n"-tier architecture"). | wiki:25699668 |
Multitier architecture | Web development usage | In the web development field, three-tier is often used to refer to websites, commonly electronic commerce websites, which are built using three tiers: | wiki:25699669 |
Multitier architecture | Other considerations | Data transfer between tiers is part of the architecture. Protocols involved may include one or more of SNMP, CORBA, Java RMI, .NET Remoting, Windows Communication Foundation, sockets, UDP, web services or other standard or proprietary protocols. Often middleware is used to connect the separate tiers. Separate tiers often (but not necessarily) run on separate physical servers, and each tier may itself run on a cluster. | wiki:25699670 |
Multitier architecture | Traceability | The end-to-end traceability of data flows through "n"-tier systems is a challenging task which becomes more important when systems increase in complexity. The Application Response Measurement defines concepts and APIs for measuring performance and correlating transactions between tiers. Generally, the term "tiers" is used to describe physical distribution of components of a system on separate servers, computers, or networks (processing nodes). A three-tier architecture then will have three processing nodes. The term "layers" refers to a logical grouping of components which may or may not be physically located on one processing node. | wiki:25699671 |
Myrinet | Introduction | Myrinet, ANSI/VITA 26-1998, is a high-speed local area networking system designed by the company Myricom to be used as an interconnect between multiple machines to form computer clusters. | wiki:25699672 |
Myrinet | Description | Myrinet was promoted as having lower protocol overhead than standards such as Ethernet, and therefore better throughput, less interference, and lower latency while using the host CPU. Although it can be used as a traditional networking system, Myrinet is often used directly by programs that "know" about it, thereby bypassing a call into the operating system. Myrinet physically consists of two fibre optic cables, upstream and downstream, connected to the host computers with a single connector. Machines are connected via low-overhead routers and switches, as opposed to connecting one machine directly to another. Myrinet includes a number of fault-tolerance features, mostly backed by the switches. | wiki:25699673 |
Myrinet | Description | These include flow control, error control, and "heartbeat" monitoring on every link. The "fourth-generation" Myrinet, called Myri-10G, supported a 10 Gbit/s data rate and can use 10 Gigabit Ethernet on PHY, the physical layer (cables, connectors, distances, signaling). Myri-10G started shipping at the end of 2005. Myrinet was approved in 1998 by the American National Standards Institute for use on the VMEbus as ANSI/VITA 26-1998.. One of the earliest publications on Myrinet is a 1995 IEEE article. | wiki:25699674 |
Myrinet | Performance | Myrinet is a lightweight protocol with little overhead that allows it to operate with throughput close to the basic signaling speed of the physical layer. For supercomputing, the low latency of Myrinet is even more important than its throughput performance, since, according to Amdahl's law, a high-performance parallel system tends to be bottlenecked by its slowest sequential process, which in all but the most embarrassingly parallel supercomputer workloads is often the latency of message transmission across the network. | wiki:25699675 |
Myrinet | Deployment | According to Myricom, 141 (28.2%) of the June 2005 TOP500 supercomputers used Myrinet technology. In the November 2005 TOP500, the number of supercomputers using Myrinet was down to 101 computers, or 20.2%, in November 2006, 79 (15.8%), and by November 2007, 18 (3.6%), a long way behind gigabit Ethernet at 54% and InfiniBand at 24.2%. In the June 2014 TOP500 list, the number of supercomputers using Myrinet interconnect was 1 (0.2%). In November, 2013, the assets of Myricom (including the Myrinet technology) were acquired by CSP Inc. In 2016, it was reported that Google had also offered to buy the company. | wiki:25699676 |
Musique concrète | Introduction | Musique concrète (; ) is a type of music composition that utilizes recorded sounds as raw material . Sounds are often modified through the application of audio effects and tape manipulation techniques, and may be assembled into a form of montage . It can feature sounds derived from recordings of musical instruments, the human voice, and the natural environment as well as those created using synthesizers and computer-based digital signal processing. Compositions in this idiom are not restricted to the normal musical rules of melody, harmony, rhythm, metre, and so on. It exploits acousmatic listening, meaning sound identities can often be intentionally obscured or appear unconnected to their source cause. | wiki:25699677 |
Musique concrète | Introduction | The theoretical basis of "musique concrète" as a compositional practice was developed by French composer Pierre Schaeffer beginning in the early 1940s, and originally contrasted with "pure" "elektronische Musik" (based solely on the use of electronically produced sounds rather than recorded sounds). Schaeffer's work resulted in the establishment of France's Groupe de Recherches de Musique Concrète (GRMC), which attracted important figures including Pierre Henry, Luc Ferrari, Pierre Boulez, Karlheinz Stockhausen, Edgar Varèse, and Iannis Xenakis. From the late 1960s onward, and particularly in France, the term acousmatic music ("musique acousmatique") started to be used in reference to fixed media compositions that utilized both musique concrète based techniques and live sound spatialisation. | wiki:25699678 |
Musique concrète | Beginnings | In 1928 music critic André Cœuroy wrote in his book "Panorama of Contemporary Music" that "perhaps the time is not far off when a composer will be able to represent through recording, music specifically composed for the gramophone" . In the same period the American composer Henry Cowell, in referring to the projects of Nikolai Lopatnikoff, believed that "there was a wide field open for the composition of music for phonographic discs." This sentiment was echoed further in 1930 by Igor Stravinsky, when he stated in the revue "Kultur und Schallplatte" that "there will be a greater interest in creating music in a way that will be peculiar to the gramophone record." The following year, 1931, Boris de Schloezer also expressed the opinion that one could write for the gramophone or for the wireless just as one can for the piano or the violin . | wiki:25699679 |
Musique concrète | Beginnings | Shortly after, German art theorist Rudolf Arnheim discussed the effects of microphonic recording in an essay entitled "Radio", published in 1936. In it the idea of a creative role for the recording medium was introduced and Arnheim stated that: "The rediscovery of the musicality of sound in noise and in language, and the reunification of music, noise and language in order to obtain a unity of material: that is one of the chief artistic tasks of radio" . | wiki:25699680 |
Musique concrète | Pierre Schaeffer and Studio d'Essai | In 1942 French composer and theoretician Pierre Schaeffer began his exploration of radiophony when he joined Jacques Copeau and his pupils in the foundation of the Studio d'Essai de la Radiodiffusion nationale. The studio originally functioned as a center for the Resistance movement in French radio, which in August 1944 was responsible for the first broadcasts in liberated Paris. It was here that Schaeffer began to experiment with creative radiophonic techniques using the sound technologies of the time . The development of Schaeffer's practice was informed by encounters with voice actors, and microphone usage and radiophonic art played an important part in inspiring and consolidating Schaeffer's conception of sound-based composition . | wiki:25699681 |
Musique concrète | Pierre Schaeffer and Studio d'Essai | Another important influence on Schaeffer's practice was cinema, and the techniques of recording and montage, which were originally associated with cinematographic practice, came to "serve as the substrate of musique concrète." Marc Battier notes that, prior to Schaeffer, Jean Epstein drew attention to the manner in which sound recording revealed what was hidden in the act of basic acoustic listening. Epstein's reference to this "phenomenon of an epiphanic being", which appears through the transduction of sound, proved influential on Schaeffer's concept of reduced listening. Schaeffer would explicitly cite Jean Epstein with reference to his use of extra-musical sound material. Epstein had already imagined that "through the transposition of natural sounds, it becomes possible to create chords and dissonances, melodies and symphonies of noise, which are a new and specifically cinematographic music" . | wiki:25699682 |
Musique concrète | Halim El-Dabh's tape music | Perhaps earlier than Schaeffer conducting his preliminary experiments into sound manipulation (assuming these were later than 1944, and not as early as the foundation of the Studio d'Essai in 1942) was the activity of Egyptian composer Halim El-Dabh. As a student in Cairo in the early to mid-1940s he began experimenting with "tape music" using a cumbersome wire recorder. He recorded the sounds of an ancient "zaar" ceremony and at the Middle East Radio studios processed the material using reverberation, echo, voltage controls, and re-recording. The resulting tape-based composition, entitled "The Expression of Zaar", was presented in 1944 at an art gallery event in Cairo. | wiki:25699683 |
Musique concrète | Halim El-Dabh's tape music | El-Dabh has described his initial activities as an attempt to unlock "the inner sound" of the recordings. While his early compositional work was not widely known outside of Egypt at the time, El-Dabh would eventually gain recognition for his influential work at the Columbia-Princeton Electronic Music Center in the late 1950s . | wiki:25699684 |
Musique concrète | Club d'Essai and Cinq études de bruits | Following Schaeffer's work with Studio d'Essai at Radiodiffusion Nationale during the early 1940s he was credited with originating the theory and practice of "musique concrète." The Studio d'Essai was renamed Club d'Essai de la Radiodiffusion-Télévision Française in 1946 and in the same year Schaeffer discussed, in writing, the question surrounding the transformation of time perceived through recording. The essay evidenced knowledge of sound manipulation techniques he would further exploit compositionally. In 1948 Schaeffer formally initiated "research in to noises" at the Club d'Essai and on 5 October 1948 the results of his initial experimentation were premiered at a concert given in Paris . | wiki:25699685 |
Musique concrète | Club d'Essai and Cinq études de bruits | Five works for phonograph (known collectively as "Cinq études de bruits"—Five Studies of Noises) including "Étude violette" ("Study in Purple") and "Étude aux chemins de fer" (Study with Railroads), were presented. | wiki:25699686 |
Musique concrète | Musique concrète | By 1949 Schaeffer's compositional work was known publicly as "musique concrète" . Schaeffer stated: "when I proposed the term 'musique concrète,' I intended … to point out an opposition with the way musical work usually goes. Instead of notating musical ideas on paper with the symbols of solfege and entrusting their realization to well-known instruments, the question was to collect concrete sounds, wherever they came from, and to abstract the musical values they were potentially containing" . According to Pierre Henry, "musique concrète was not a study of timbre, it is focused on envelopes, forms. It must be presented by means of non-traditional characteristics, you see … one might say that the origin of this music is also found in the interest in 'plastifying' music, of rendering it plastic like sculpture…musique concrète, in my opinion … led to a manner of composing, indeed, a new mental framework of composing" . | wiki:25699687 |
Musique concrète | Musique concrète | Schaeffer had developed an aesthetic that was centred upon the use of sound as a primary compositional resource. The aesthetic also emphasised the importance of play ("jeu") in the practice of sound based composition. Schaeffer's use of the word "jeu", from the verb "jouer", carries the same double meaning as the English verb play: 'to enjoy oneself by interacting with one's surroundings', as well as 'to operate a musical instrument' . | wiki:25699688 |
Musique concrète | Groupe de Recherche de Musique Concrète | By 1951 the work of Schaeffer, composer-percussionist Pierre Henry, and sound engineer Jacques Poullin had received official recognition and The Groupe de Recherches de Musique Concrète, Club d 'Essai de la Radiodiffusion-Télévision Française was established at RTF in Paris, the ancestor of the ORTF . At RTF the GRMC established the first purpose-built electroacoustic music studio. It quickly attracted many who either were or were later to become notable composers, including Olivier Messiaen, Pierre Boulez, Jean Barraqué, Karlheinz Stockhausen, Edgard Varèse, Iannis Xenakis, Michel Philippot, and Arthur Honegger. Compositional "output from 1951 to 1953 comprised "Étude I" (1951) and "Étude II" (1951) by Boulez, "Timbres-durées" (1952) by Messiaen, "Étude aux mille collants" (1952) by Stockhausen, "Le microphone bien tempéré" (1952) and "La voile d'Orphée" (1953) by Henry, "Étude I" (1953) by Philippot, "Étude" (1953) by Barraqué, the mixed pieces "Toute la lyre" (1951) and "Orphée 53" (1953) by Schaeffer/Henry, and the film music "Masquerage" (1952) by Schaeffer and "Astrologie" (1953) by Henry. | wiki:25699689 |
Musique concrète | Groupe de Recherche de Musique Concrète | In 1954 Varèse and Honegger visited to work on the tape parts of "Déserts" and "La rivière endormie"" . In the early and mid 1950s Schaeffer's commitments to RTF included official missions which often required extended absences from the studios. This led him to invest Philippe Arthuys with responsibility for the GRMC in his absence, with Pierre Henry operating as Director of Works. Pierre Henry's composing talent developed greatly during this period at the GRMC and he worked with experimental filmmakers such as Max de Haas, Jean Grémillon, Enrico Fulchignoni, and Jean Rouch, and with choreographers including Dick Sanders and Maurice Béjart . | wiki:25699690 |
Musique concrète | Groupe de Recherche de Musique Concrète | Schaeffer returned to run the group at the end of 1957, and immediately stated his disapproval of the direction the GRMC had taken. A proposal was then made to "renew completely the spirit, the methods and the personnel of the Group, with a view to undertake research and to offer a much needed welcome to young composers" . | wiki:25699691 |
Musique concrète | Groupe de Recherches Musicales | Following the emergence of differences within the GRMC Pierre Henry, Philippe Arthuys, and several of their colleagues, resigned in April 1958. Schaeffer created a new collective, called Groupe de Recherches Musicales (GRM) and set about recruiting new members including Luc Ferrari, Beatriz Ferreyra, François-Bernard Mâche, Iannis Xenakis, Bernard Parmegiani, and Mireille Chamass-Kyrou. Later arrivals included Ivo Malec, Philippe Carson, Romuald Vandelle, Edgardo Canton and François Bayle . GRM was one of several theoretical and experimental groups working under the umbrella of the Schaeffer-led Service de la Recherche at ORTF (1960–74). Together with the GRM, three other groups existed: the Groupe de Recherches Image GRI, the Groupe de Recherches Technologiques GRT and the Groupe de Recherches which became the Groupe d'Etudes Critiques . | wiki:25699692 |
Musique concrète | Groupe de Recherches Musicales | Communication was the one theme that unified the various groups, all of which were devoted to production and creation. In terms of the question "who says what to whom?" Schaeffer added "how?", thereby creating a platform for research into audiovisual communication and mass media, audible phenomena and music in general (including non-Western musics) (Beatriz Ferreyra, new preface to Schaeffer and Reibel 1967, reedition of 1998, 9). At the GRM the theoretical teaching remained based on practice and could be summed up in the catch phrase "do and listen" . Schaeffer kept up a practice established with the GRMC of delegating the functions (though not the title) of Group Director to colleagues. | wiki:25699693 |
Musique concrète | Groupe de Recherches Musicales | Since 1961 GRM has had six Group Directors: Michel Philippot (1960–61), Luc Ferrari (1962–63), Bernard Baschet and François Vercken (1964–66). From the beginning of 1966, François Bayle took over the direction for the duration of thirty-one years, to 1997. He was then replaced by Daniel Teruggi . | wiki:25699694 |
Musique concrète | Traité des objets musicaux | The group continued to refine Schaeffer's ideas and strengthened the concept of "musique acousmatique" . Schaeffer had borrowed the term acousmatic from Pythagoras and defined it as: ""Acousmatic, adjective: referring to a sound that one hears without seeing the causes behind it"" . In 1966 Schaeffer published the book "Traité des objets musicaux" (Treatise on Musical Objects) which represented the culmination of some 20 years of research in the field of "musique concrète". In conjunction with this publication, a set of sound recordings was produced, entitled "Le solfège de l'objet sonore" (Music Theory of the Acoustic Object), to provide examples of concepts dealt with in the treatise. | wiki:25699695 |
Musique concrète | Technology | The development of musique concrète was facilitated by the emergence of new music technology in post-war Europe. Access to microphones, phonographs, and later magnetic tape recorders (created in 1939 and acquired by the Schaeffer's Groupe de Recherche de Musique Concrète (Research Group on Concrete Music) in 1952), facilitated by an association with the French national broadcasting organization, at that time the Radiodiffusion-Télévision Française, gave Schaeffer and his colleagues an opportunity to experiment with recording technology and tape manipulation. | wiki:25699696 |
Musique concrète | Initial tools of musique concrète | In 1948, a typical radio studio consisted of a series of shellac record players, a shellac record recorder, a mixing desk with rotating potentiometers, mechanical reverberation, filters, and microphones. This technology made a number of limited operations available to a composer (, ): The application of the above technologies in the creation of musique concrète led to the development of a number of sound manipulation techniques including (, ): | wiki:25699697 |
Musique concrète | Magnetic tape | The first tape recorders started arriving at ORTF in 1949; however, their functioning was much less reliable than the shellac players, to the point that the "Symphonie pour un homme seul", which was composed in 1950–51, was mainly composed with records, even if the tape recorder was available . In 1950, when the machines finally functioned correctly, the techniques of musique concrète were expanded. A range of new sound manipulation practices were explored using improved media manipulation methods and operations such as speed variation. A completely new possibility of organising sounds appears with tape editing, which permits tape to be spliced and arranged with an extraordinary new precision. | wiki:25699698 |
Musique concrète | Magnetic tape | The "axe-cut junctions" were replaced with micrometric junctions and a whole new technique of production, less dependency on performance skills, could be developed. Tape editing brought a new technique called "micro-editing", in which very tiny fragments of sound, representing milliseconds of time, were edited together, thus creating completely new sounds or structures . | wiki:25699699 |
Musique concrète | Development of novel devices | During the GRMC period from 1951–1958 time Schaeffer and Jacques Poullin developed a number of novel sound creation tools including a three-track tape recorder, a machine with ten playback heads to replay tape loops in echo (the morphophone), a keyboard-controlled machine to replay tape loops at twenty-four preset speeds (the keyboard, chromatic, or Tolana phonogène), a slide-controlled machine to replay tape loops at a continuously variable range of speeds (the handle, continuous, or Sareg phonogène), and a device to distribute an encoded track across four loudspeakers, including one hanging from the centre of the ceiling (the potentiomètre d'espace) . | wiki:25699700 |