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74-503: MMIX is a computer intended to illustrate machine-level aspects of programming. In my books The Art of Computer Programming , it replaces MIX , the 1960s-style machine that formerly played such a role… I strove to design MMIX so that its machine language would be simple, elegant, and easy to learn. At the same time I was careful to include all of the complexities needed to achieve high performance in practice, so that MMIX could in principle be built and even perhaps be competitive with some of

148-422: A trap ) is a request for the processor to interrupt currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, the processor will suspend its current activities, save its state , and execute a function called an interrupt handler (or an interrupt service routine , ISR) to deal with the event. This interruption is often temporary, allowing

222-401: A 64-bit virtual address space . The MMIX instruction set comprises 256 opcodes, one of which is reserved for future expansion. MMIX uses IEEE 754 floating-point numbers. All instructions have an associated mnemonic. For example, instruction #20 (32 decimal) is associated with ADD. Most instructions have the symbolic form OP X,Y,Z , where OP specifies the sort of instruction, X specifies

296-400: A common source of preemption interrupts . Many instructions cause an interrupt in certain exceptional cases; such as the memory protection page fault exceptions used to implement virtual memory, and floating point exception handling . MMIX has 2 kinds of interrupts: "trips" and "traps". The main difference between "trips" and "traps" is that traps send control to a "trap handler" program in

370-571: A considerable extent. Some devices with a poorly designed programming interface provide no way to determine whether they have requested service. They may lock up or otherwise misbehave if serviced when they do not want it. Such devices cannot tolerate spurious interrupts, and so also cannot tolerate sharing an interrupt line. ISA cards, due to often cheap design and construction, are notorious for this problem. Such devices are becoming much rarer, as hardware logic becomes cheaper and new system architectures mandate shareable interrupts. Some systems use

444-506: A continuous series by this title." American Scientist has included this work among "100 or so Books that shaped a Century of Science", referring to the twentieth century. Covers of the third edition of Volume 1 quote Bill Gates as saying, "If you think you're a really good programmer… read (Knuth's) Art of Computer Programming … You should definitely send me a résumé if you can read the whole thing." The New York Times referred to it as "the profession's defining treatise". These are

518-453: A device, the processor may again poll and, if necessary, service other devices before exiting the ISR. An edge-triggered interrupt is an interrupt signaled by a level transition on the interrupt line, either a falling edge (high to low) or a rising edge (low to high). A device wishing to signal an interrupt drives a pulse onto the line and then releases the line to its inactive state. If the pulse

592-410: A further interrupt. This contrasts with a level trigger where the low level would continue to create interrupts (if they are enabled) until the signal returns to its high level. Computers with edge-triggered interrupts may include an interrupt register that retains the status of pending interrupts. Systems with interrupt registers generally have interrupt mask registers as well. The processor samples

666-452: A hybrid of level-triggered and edge-triggered signaling. The hardware not only looks for an edge, but it also verifies that the interrupt signal stays active for a certain period of time. A common use of a hybrid interrupt is for the NMI (non-maskable interrupt) input. Because NMIs generally signal major – or even catastrophic – system events, a good implementation of this signal tries to ensure that

740-413: A particular (rising or falling) edge will cause a service request to be latched; the processor resets the latch when the interrupt handler executes. A level-triggered interrupt is requested by holding the interrupt signal at its particular (high or low) active logic level . A device invokes a level-triggered interrupt by driving the signal to and holding it at the active level. It negates the signal when

814-960: A period - and unless there is some type of hardware latch that records the event it is impossible to recover. This problem caused many "lockups" in early computer hardware because the processor did not know it was expected to do something. More modern hardware often has one or more interrupt status registers that latch interrupts requests; well-written edge-driven interrupt handling code can check these registers to ensure no events are missed. The Industry Standard Architecture (ISA) bus uses edge-triggered interrupts, without mandating that devices be able to share IRQ lines, but all mainstream ISA motherboards include pull-up resistors on their IRQ lines, so well-behaved ISA devices sharing IRQ lines should just work fine. The parallel port also uses edge-triggered interrupts. Many older devices assume that they have exclusive use of IRQ lines, making it electrically unsafe to share them. There are three ways multiple devices "sharing

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888-501: A restart of the program. Arm uses the term exception to refer to all types of interrupts, and divides exceptions into (hardware) interrupts , aborts , reset , and exception-generating instructions. Aborts correspond to x86 exceptions and may be prefetch aborts (failed instruction fetches) or data aborts (failed data accesses), and may be synchronous or asynchronous. Asynchronous aborts may be precise or imprecise. MMU aborts (page faults) are synchronous. RISC-V uses interrupt as

962-475: A seven-volume set were published in 1968, 1969, and 1973. Work began in earnest on Volume 4 in 1973, but was suspended in 1977 for work on typesetting prompted by the second edition of Volume 2. Writing of the final copy of Volume 4A began in longhand in 2001, and the first online pre-fascicle, 2A, appeared later in 2001. The first published installment of Volume 4 appeared in paperback as Fascicle 2 in 2005. The hardback Volume 4A, combining Volume 4, Fascicles 0–4,

1036-429: A synchronous interrupt caused by an exceptional condition (e.g., division by zero , invalid memory access , illegal opcode ), although the term exception is more common for this. x86 divides interrupts into (hardware) interrupts and software exceptions , and identifies three types of exceptions: faults, traps, and aborts. (Hardware) interrupts are interrupts triggered asynchronously by an I/O device, and allow

1110-418: A system misbehaves. In a wired-OR circuit, parasitic capacitance charging/discharging through the interrupt line's bias resistor will cause a small delay before the processor recognizes that the interrupt source has been cleared. If the interrupting device is cleared too late in the interrupt service routine (ISR), there will not be enough time for the interrupt circuit to return to the quiescent state before

1184-467: A topic of discussion among the mathematics department, which included Richard S. Varga . In January 1962, when he was a graduate student in the mathematics department at Caltech, Knuth was approached by Addison-Wesley to write a book about compiler design, and he proposed a larger scope. He came up with a list of twelve chapter titles the same day. In the summer of 1962 he worked on a FORTRAN compiler for UNIVAC , considering that he had "sold my soul to

1258-517: A trigger table (a table of functions) in its header, which both the app and OS know of and use appropriately that is not related to hardware. However do not confuse this with hardware interrupts which signal the CPU (the CPU enacts software from a table of functions, similarly to software interrupts). Multiple devices sharing an interrupt line (of any triggering style) all act as spurious interrupt sources with respect to each other. With many devices on one line,

1332-577: A type reserved for interrupts, or it might be of some pre-existing type such as a memory write. Message-signalled interrupts behave very much like edge-triggered interrupts, in that the interrupt is a momentary signal rather than a continuous condition. Interrupt-handling software treats the two in much the same manner. Typically, multiple pending message-signaled interrupts with the same message (the same virtual interrupt line) are allowed to merge, just as closely spaced edge-triggered interrupts can merge. Message-signalled interrupt vectors can be shared, to

1406-404: A variety of purposes, such as requesting operating system services and interacting with device drivers (e.g., to read or write storage media). Software interrupts may also be triggered by program execution errors or by the virtual memory system. Typically, the operating system kernel will catch and handle such interrupts. Some interrupts are handled transparently to the program - for example,

1480-408: Is a comprehensive monograph written by the computer scientist Donald Knuth presenting programming algorithms and their analysis . Volumes 1–5 are intended to represent the central core of computer programming for sequential machines. When Knuth began the project in 1962, he originally conceived of it as a single book with twelve chapters. The first three volumes of what was then expected to be

1554-410: Is currently used for all volumes. Another characteristic of the volumes is the variation in the difficulty of the exercises including a numerical rating varying from 0 to 50, where 0 is trivial, and 50 is an open question in contemporary research. The offer of a so-called Knuth reward check worth "one hexadecimal dollar" (100 HEX base 16 cents, in decimal , is $ 2.56) for any errors found, and

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1628-411: Is deferred or ignored by the processor, while to unmask an interrupt is to enable it. Processors typically have an internal interrupt mask register, which allows selective enabling (and disabling) of hardware interrupts. Each interrupt signal is associated with a bit in the mask register. On some systems, the interrupt is enabled when the bit is set, and disabled when the bit is clear. On others,

1702-421: Is no OS, from the bare metal program running on the CPU. Such external devices may be part of the computer (e.g., disk controller ) or they may be external peripherals . For example, pressing a keyboard key or moving a mouse plugged into a PS/2 port triggers hardware interrupts that cause the processor to read the keystroke or mouse position. Hardware interrupts can arrive asynchronously with respect to

1776-416: Is no clear consensus as to the exact meaning of these terms". The term trap may refer to any interrupt, to any software interrupt, to any synchronous software interrupt, or only to interrupts caused by instructions with trap in their names. In some usages, the term trap refers specifically to a breakpoint intended to initiate a context switch to a monitor program or debugger . It may also refer to

1850-413: Is requested by the processor itself upon executing particular instructions or when certain conditions are met. Every software interrupt signal is associated with a particular interrupt handler. A software interrupt may be intentionally caused by executing a special instruction which, by design, invokes an interrupt when executed. Such instructions function similarly to subroutine calls and are used for

1924-427: Is the default state of it. Devices signal an interrupt by briefly driving the line to its non-default state, and let the line float (do not actively drive it) when not signaling an interrupt. This type of connection is also referred to as open collector . The line then carries all the pulses generated by all the devices. (This is analogous to the pull cord on some buses and trolleys that any passenger can pull to signal

1998-440: Is too short to be detected by polled I/O then special hardware may be required to detect it. The important part of edge triggering is that the signal must transition to trigger the interrupt; for example, if the signal was high-low-low, there would only be one falling edge interrupt triggered, and the continued low level would not trigger a further interrupt. The signal must return to the high level and fall again in order to trigger

2072-457: The 1964 CDC 3600 , all interrupts went to the same location, and the OS used a specialized instruction to determine the highest-priority outstanding unmasked interrupt. On contemporary systems, there is generally a distinct interrupt routine for each type of interrupt (or for each interrupt source), often implemented as one or more interrupt vector tables . To mask an interrupt is to disable it, so it

2146-406: The CPU and another component such as a programmable interrupt controller or a southbridge . If an additional component is used, that component would be connected between the interrupting device and the processor's interrupt pin to multiplex several sources of interrupt onto the one or two CPU lines typically available. If implemented as part of the memory controller , interrupts are mapped into

2220-447: The ISR does not account for the possibility of such an interrupt occurring. As spurious interrupts are mostly a problem with wired-OR interrupt circuits, good programming practice in such systems is for the ISR to check all interrupt sources for activity and take no action (other than possibly logging the event) if none of the sources is interrupting. They may even lead to crashing of the computer in adverse scenarios. A software interrupt

2294-552: The MMIX instruction set architecture exist. However, the fpgammix project implements MMIX in Verilog , making it possible to implement using a field-programmable gate array . The MMIX instruction set architecture is supported by a number of software tools for computer architecture research and software development. The GNU Compiler Collection includes an MMIX back-end for its C / C++ compilers, contributed by Hans-Peter Nilsson and part of

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2368-520: The MMIXAL assembly language. The below is a simple MMIXAL program, which prints the string " Hello, world! ": There are 256 directly addressable general-purpose architectural registers in an MMIX chip, designated by $ 0 through $ 255, and 32 special-purpose architectural registers. The special-purpose registers can be accessed with the GET and PUT instructions. Two of the special registers, rL and rG, determine which of

2442-492: The VARY ONLINE command will simulate a device end interrupt on the target device. A spurious interrupt is a hardware interrupt for which no source can be found. The term "phantom interrupt" or "ghost interrupt" may also be used to describe this phenomenon. Spurious interrupts tend to be a problem with a wired-OR interrupt circuit attached to a level-sensitive processor input. Such interrupts may be difficult to identify when

2516-456: The callback is made using Structured Exception Handling with an exception code such as STATUS_ACCESS_VIOLATION or STATUS_INTEGER_DIVIDE_BY_ZERO. In a kernel process , it is often the case that some types of software interrupts are not supposed to happen. If they occur nonetheless, an operating system crash may result. The terms interrupt , trap , exception , fault , and abort are used to distinguish types of interrupts, although "there

2590-540: The correction of these errors in subsequent printings, has contributed to the highly polished and still-authoritative nature of the work, long after its first publication. All examples in the books use a hypothetical language called " MIX assembly language" (MIXAL), which runs on "a mythical computer called MIX". Currently, the MIX computer is being replaced by the MMIX computer, which is a RISC version. The conversion from MIX to MMIX

2664-530: The current editions in order by volume number: These volumes were superseded by newer editions and are in order by date. Volume 4, Fascicles 0–4 were revised and published as Volume 4A. Volume 4, Fascicles 5–6 were revised and published as Volume 4B. Volume 1 Volume 4 The remaining pre-fascicles contain draft material that is set to appear in future fascicles and volumes. Notes Citations Sources Software interrupt In digital computers , an interrupt (sometimes referred to as

2738-608: The current instance of the ISR terminates. The result is the processor will think another interrupt is pending, since the voltage at its interrupt request input will be not high or low enough to establish an unambiguous internal logic 1 or logic 0. The apparent interrupt will have no identifiable source, hence the "spurious" moniker. A spurious interrupt may also be the result of electrical anomalies due to faulty circuit design, high noise levels, crosstalk , timing issues, or more rarely, device errata . A spurious interrupt may result in system deadlock or other undefined operation if

2812-855: The devil" to develop a FORTRAN compiler after ALGOL developments with Burroughs. He remained as a consultant to Burroughs over the period 1960 to 1968 while writing Volume 1 'Fundamental Algorithms'. During this time, he also developed a mathematical analysis of linear probing , which convinced him to present the material with a quantitative approach. After receiving his Ph.D. in June 1963, he began working on his manuscript, of which he finished his first draft in June 1965, at 3000 hand-written pages. He had assumed that about five hand-written pages would translate into one printed page, but his publisher said instead that about 1 + 1 ⁄ 2 hand-written pages translated to one printed page. This meant he had approximately 2000 printed pages of material, which closely matches

2886-410: The driver that they are requesting a stop.) However, interrupt pulses from different devices may merge if they occur close in time. To avoid losing interrupts the CPU must trigger on the trailing edge of the pulse (e.g. the rising edge if the line is pulled up and driven low). After detecting an interrupt the CPU must check all the devices for service requirements. Edge-triggered interrupts do not suffer

2960-451: The failure might affect only a single process or might have global impact. Some operating systems have code specifically to deal with this. As an example, IBM Operating System/360 (OS/360) relies on a not-ready to ready device-end interrupt when a tape has been mounted on a tape drive, and will not read the tape label until that interrupt occurs or is simulated. IBM added code in OS/360 so that

3034-587: The fastest general-purpose computers in the marketplace." Knuth started the design of MMIX in 1999, and released the stable version of the design in 2011. The processor is numbered as "2009" with Knuth explaining that this is the arithmetic mean from the numbers of other computer architectures; as well as being "MMIX" in Roman numerals . MMIX is a big-endian 64-bit reduced instruction set computer (RISC), with 256 64-bit general-purpose registers, 32 64-bit special-purpose registers, fixed-length 32-bit instructions and

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3108-615: The first occurrence of interrupt masking. The National Bureau of Standards DYSEAC (1954) was the first to use interrupts for I/O. The IBM 704 was the first to use interrupts for debugging , with a "transfer trap", which could invoke a special routine when a branch instruction was encountered. The MIT Lincoln Laboratory TX-2 system (1957) was the first to provide multiple levels of priority interrupts. Interrupt signals may be issued in response to hardware or software events. These are classified as hardware interrupts or software interrupts , respectively. For any particular processor,

3182-518: The general registers are local and which are global. All registers from $ 0... ([rL] − 1) are local registers, and represent a window into an internal stack of registers. Registers from [rL]... ([rG] − 1) are "marginal registers", they always return 0 if they are used as a source in an operation. Using a marginal register as the destination of an operation will cause the machine to automatically increase rL to include that register. All registers [rG]... $ 255 are called global registers, and are not part of

3256-554: The growth in Chapter 7, which was fewer than 100 pages of the 1965 manuscript, per Vol. 4A p. vi, the plan for Volume 4 has since expanded to include Volumes 4A, 4B, 4C, 4D, and possibly more. In 1976, Knuth prepared a second edition of Volume 2, requiring it to be typeset again, but the style of type used in the first edition (called hot type ) was no longer available. In 1977, he decided to spend some time creating something more suitable. Eight years later, he returned with T E X , which

3330-401: The highest priority enabled interrupt. In others, there are separate interrupt handlers for separate interrupt types, separate I/O channels or devices, or both. Several interrupt causes may have the same interrupt type and thus the same interrupt handler, requiring the interrupt handler to determine the cause. Interrupts may be fully handled in hardware by the CPU, or may be handled by both

3404-564: The internal stack can contain only a finite number of registers, it may be necessary to store a part of the stack in memory. This is implemented with the special registers rO and rS which record which part of the local register stack is in memory and which part is still in local physical registers. The register stack provides for fast subroutine linkage. The 32 special physical architectural registers are as follows: Like programs running on almost all other CPUs, MMIX programs can be interrupted in several ways. External hardware, such as timers, are

3478-400: The interrupt is valid by verifying that it remains active for a period of time. This 2-step approach helps to eliminate false interrupts from affecting the system. A message-signaled interrupt does not use a physical interrupt line. Instead, a device signals its request for service by sending a short message over some communications medium, typically a computer bus . The message might be of

3552-440: The interrupt trigger signals or interrupt register during each instruction cycle, and will process the highest priority enabled interrupt found. Regardless of the triggering method, the processor will begin interrupt processing at the next instruction boundary following a detected trigger, thus ensuring: There are several different architectures for handling interrupts. In some, there is a single interrupt handler that must scan for

3626-498: The main GCC distribution since late 2001. As of November 2017, the MMIX back-end to GCC continues to be actively developed and maintained by volunteers. The above tools could theoretically be used to compile, build, and bootstrap an entire FreeBSD , Linux , or other similar operating system kernel onto MMIX hardware, were such hardware to exist. The Art of Computer Programming The Art of Computer Programming ( TAOCP )

3700-423: The normal resolution of a page fault is to make the required page accessible in physical memory. But in other cases such as a segmentation fault the operating system executes a process callback. On Unix-like operating systems this involves sending a signal such as SIGSEGV , SIGBUS , SIGILL or SIGFPE , which may either call a signal handler or execute a default action (terminating the program). On Windows

3774-481: The number of interrupt types is limited by the architecture. A hardware interrupt is a condition related to the state of the hardware that may be signaled by an external hardware device, e.g., an interrupt request (IRQ) line on a PC, or detected by devices embedded in processor logic (e.g., the CPU timer in IBM System/370), to communicate that the device needs attention from the operating system (OS) or, if there

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3848-455: The operating system (trapping), but trips send control to a "trip handler" program in the user application (tripping). Users can also force any interrupt handler to run with explicit software interrupt instructions TRIP and TRAP, similar to some kinds of trap in other computer systems. In particular, a system call from a user program to the operating system uses a TRAP instruction. As of October 2015, no known hardware implementations of

3922-414: The overall term as well as for the external subset; internal interrupts are called exceptions. Each interrupt signal input is designed to be triggered by either a logic signal level or a particular signal edge (level transition). Level-sensitive inputs continuously request processor service so long as a particular (high or low) logic level is applied to the input. Edge-sensitive inputs react to signal edges:

3996-662: The preface, he thanks first his wife Jill, then Burroughs for the use of B220 and B5500 computers in testing most of the programs, and Caltech, the National Science Foundation, and the Office of Naval Research. Section 2.5 of ‘Fundamental Algorithms’ is on Dynamic Storage Allocation . Parts of this are used in the Burroughs approach to memory management. Knuth claims credit for “The “boundary-tag” method, introduced in Section 2.5,

4070-489: The problems that level-triggered interrupts have with sharing. Service of a low-priority device can be postponed arbitrarily, while interrupts from high-priority devices continue to be received and get serviced. If there is a device that the CPU does not know how to service, which may raise spurious interrupts, it will not interfere with interrupt signaling of other devices. However, it is easy for an edge-triggered interrupt to be missed - for example, when interrupts are masked for

4144-478: The processor clock, and at any time during instruction execution. Consequently, all incoming hardware interrupt signals are conditioned by synchronizing them to the processor clock, and acted upon only at instruction execution boundaries. In many systems, each device is associated with a particular IRQ signal. This makes it possible to quickly determine which hardware device is requesting service, and to expedite servicing of that device. On some older systems, such as

4218-458: The processor commands it to do so, typically after the device has been serviced. The processor samples the interrupt input signal during each instruction cycle. The processor will recognize the interrupt request if the signal is asserted when sampling occurs. Level-triggered inputs allow multiple devices to share a common interrupt signal via wired-OR connections. The processor polls to determine which devices are requesting service. After servicing

4292-511: The program to be restarted with no loss of continuity. A fault is restartable as well but is tied to the synchronous execution of an instruction - the return address points to the faulting instruction. A trap is similar to a fault except that the return address points to the instruction to be executed after the trapping instruction; one prominent use is to implement system calls . An abort is used for severe errors, such as hardware errors and illegal values in system tables, and often does not allow

4366-426: The register stack. The local register stack provides each subroutine with its own rL local registers, designated by $ 0 through $ (rL − 1) . Whenever a subroutine is called, a number of local registers are pushed down the stack (by shifting the start of the window). The arguments of the called subroutine are left in the remaining local registers. When a subroutine finishes it pops the previously pushed registers. Because

4440-415: The register used to store the result of the instruction and the rest specify the operands of the instruction. Each of these fields is eight bits wide. For example, ADD $ 0,$ 1,3 means "Set $ 0 to the sum of $ 1 and 3." Most instructions can take either immediate values or register contents; thus a single instruction mnemonic may correspond to one of two opcodes. MMIX programs are typically constructed using

4514-418: The remote side excites the gate beyond a threshold, thus no negotiated speed is required. Each has its speed versus distance advantages. A trigger, generally, is the method in which excitation is detected: rising edge, falling edge, threshold ( oscilloscope can trigger a wide variety of shapes and conditions). Triggering for software interrupts must be built into the software (both in OS and app). A 'C' app has

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4588-498: The reverse is true, and a set bit disables the interrupt. When the interrupt is disabled, the associated interrupt signal may be ignored by the processor, or it may remain pending. Signals which are affected by the mask are called maskable interrupts . Some interrupt signals are not affected by the interrupt mask and therefore cannot be disabled; these are called non-maskable interrupts (NMIs). These indicate high-priority events which cannot be ignored under any circumstances, such as

4662-481: The same line" can be raised. First is by exclusive conduction (switching) or exclusive connection (to pins). Next is by bus (all connected to the same line listening): cards on a bus must know when they are to talk and not talk (i.e., the ISA bus). Talking can be triggered in two ways: by accumulation latch or by logic gates. Logic gates expect a continual data flow that is monitored for key signals. Accumulators only trigger when

4736-540: The size of the first three published volumes. The first volume of ‘The Art of Computer Programming’, ‘Fundamental Algorithms’, took five years to complete between 1963 and 1968 while working at both Caltech and Burroughs. Knuth's dedication in Volume 1 reads: This series of books is affectionately dedicated to the Type 650 computer once installed at Case Institute of Technology , in remembrance of many pleasant evenings. In

4810-667: The software to resume normal activities after the interrupt handler finishes, although the interrupt could instead indicate a fatal error. Interrupts are commonly used by hardware devices to indicate electronic or physical state changes that require time-sensitive attention. Interrupts are also commonly used to implement computer multitasking and system calls , especially in real-time computing . Systems that use interrupts in these ways are said to be interrupt-driven. Hardware interrupts were introduced as an optimization, eliminating unproductive waiting time in polling loops , waiting for external events. The first system to use this approach

4884-475: The system's memory address space . In systems on a chip (SoC) implementations, interrupts come from different blocks of the chip and are usually aggregated in an interrupt controller attached to one or several processors (in a multi-core system). Multiple devices may share an edge-triggered interrupt line if they are designed to. The interrupt line must have a pull-down or pull-up resistor so that when not actively driven it settles to its inactive state, which

4958-477: The time: (360 + 650 + 709 + U3 + SS80 + 1107 + 1604 + G2- + B220 + S2000 + 920 + 601 + H800 + PDP-4 + 11)/16 = 1009 or MIX. The name MMIX is 2009 in Roman numerals and Knuth claims MMIX is even nicer than MIX. Knuth was awarded the 1974 Turing Award "for his major contributions to the analysis of algorithms […], and in particular for his contributions to the 'art of computer programming' through his well-known books in

5032-472: The timeout signal from a watchdog timer . With regard to SPARC , the Non-Maskable Interrupt (NMI), despite having the highest priority among interrupts, can be prevented from occurring through the use of an interrupt mask. One failure mode is when the hardware does not generate the expected interrupt for a change in state, causing the operating system to wait indefinitely. Depending on the details,

5106-468: The workload in servicing interrupts grows in proportion to the square of the number of devices. It is therefore preferred to spread devices evenly across the available interrupt lines. Shortage of interrupt lines is a problem in older system designs where the interrupt lines are distinct physical conductors. Message-signaled interrupts, where the interrupt line is virtual, are favored in new system architectures (such as PCI Express ) and relieve this problem to

5180-457: Was a large ongoing project for which Knuth solicited volunteers for help. Software such as GNU MDK exists to provide emulation of the MIX architecture. Knuth considers the use of assembly language necessary for the speed and memory usage of algorithms to be judged. MIX was much like any computer then in existence, but nicer. The name ‘MIX’ is 1009 in Roman numerals and this is given by a formula involving series numbers of several computers of

5254-505: Was designed by the author in 1962 for use in a control program for the B5000 computer.” Knuth received support from Richard S. Varga, who was the scientific adviser to the publisher. Varga was visiting Olga Taussky-Todd and John Todd at Caltech . With Varga's enthusiastic endorsement, the publisher accepted Knuth's expanded plans. In its expanded version, the book would be published in seven volumes, each with just one or two chapters. Due to

5328-575: Was published in 2011. Volume 4, Fascicle 6 ("Satisfiability") was released in December 2015; Volume 4, Fascicle 5 ("Mathematical Preliminaries Redux; Backtracking; Dancing Links") was released in November 2019. Volume 4B consists of material evolved from Fascicles 5 and 6. The manuscript was sent to the publisher on August 1, 2022, and the volume was published in September 2022. Fascicle 7, planned for Volume 4C,

5402-520: Was the DYSEAC , completed in 1954, although earlier systems provided error trap functions. The UNIVAC 1103A computer is generally credited with the earliest use of interrupts in 1953. Earlier, on the UNIVAC I (1951) "Arithmetic overflow either triggered the execution of a two-instruction fix-up routine at address 0, or, at the programmer's option, caused the computer to stop." The IBM 650 (1954) incorporated

5476-673: Was the subject of Knuth's talk on August 3, 2022. After winning a Westinghouse Talent Search scholarship, Knuth enrolled at the Case Institute of Technology (now Case Western Reserve University ), where his performance was so outstanding that the faculty voted to award him a master of science upon his completion of the bachelor's degree . During his summer vacations, Knuth was hired by the Burroughs Corporation to write compilers , earning more in his summer months than full professors did for an entire year. Such exploits made Knuth

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