MIX

MIX

MIX is a hypothetical computer used in Donald Knuth’s monograph, "The Art of Computer Programming" ("TAOCP"). MIX’s model number is 1009, which was derived by combining the model numbers and names of several contemporaneous, commercial machines deemed significant by the author. (“MIX” also has the value 1009 in Roman numerals.)

The 1960s-era MIX has since been superseded by a new (also hypothetical) computer architecture, MMIX, to be incorporated in forthcoming editions of "TAOCP". Software implementations for both the MIX and MMIX architectures have been developed by Knuth and made freely available (named “MIXware” and “MMIXware,” respectively).

Several derivatives of Knuth’s MIX/MMIX emulators also exist. GNU MDK is one such software package; it is free and runs on a wide variety of platforms.

Their purpose for education is quite similar to John L. Hennessy's and David A. Patterson's DLX architecture, from "Computer Architecture: A Quantitative Approach".

Architecture

MIX is a hybrid binary–decimal computer. When programmed in binary, each byte has 6 bits (values range from 0 to 63). In decimal, each byte has 2 decimal digits (values range from 0 to 99). Bytes are grouped into words of five bytes plus a sign. Most programs written for MIX will work in either binary or decimal, so long as they do not try to store a value greater than 63 in a single byte.

A word has the range −1,073,741,823 to 1,073,741,823 (inclusive) in binary mode, and −9,999,999,999 to 9,999,999,999 (inclusive) in decimal mode. The sign-and-magnitude representation of integers in the MIX architecture distinguishes between “−0” and “+0.” This contrasts with modern computers, whose two’s-complement representation of integer quantities includes a single representation for zero, but whose range for a given number of bits includes one more negative integer than the number of representable positive integers.

Registers

There are 9 registers in MIX:
* rA: Accumulator (full word, five bytes and a sign).
* rX: Extension (full word, five bytes and a sign).
* rI1, rI2, rI3, rI4, rI5 rI6: Index registers (two bytes and a sign).
* rJ: Jump address (two bytes, always positive).

A byte is assumed to be at least 6 bits. Most instructions can specify "which" of the "fields" (bytes) of a register are to be altered, using a suffix of the form "(first:last)". The zeroth field is the one-bit sign.

MIX also records whether the previous operation overflowed, and has a one-trit comparison indicator (less than, equal to, or greater than). In the diagram below, each register is shown divided into its fields.

| | |

Memory and input/output

The MIX machine has 4000 words of storage (each with 5 bytes and a sign), addressed from 0 to 3999. A variety of input and output devices are also included:
*Tape units (devices 0 … 7).
*Disk or drum units (devices 8 … 15).
*Card reader (device 16).
*Card punch (device 17).
*Line printer (device 18).
*Typewriter terminal (device 19).
*Paper tape (device 20).

Instructions

Each machine instruction in memory occupies one word, and consists of 4 parts: the address (2 bytes and the sign of the word) in memory to read or write; an index specification (1 byte, describing which rI index register to use) to add to the address; a modification (1 byte) that specifies which parts of the register or memory location will be read or altered; and the operation code (1 byte). All operation codes have an associated mnemonic.

MIX programs frequently use self-modifying code, in particularto return from a subroutine, as MIX lacks an automatic subroutine return stack. Self-modifying code is facilitated by the modification byte, allowing the program to store data to, for example, the address part of the target instruction, leaving the rest of the instruction unmodified.

MIX programs are typically constructed using the MIXAL assembly language; for an example, see the [http://en.wikibooks.org/wiki/List_of_hello_world_programs#General-purpose_fictional_computer:_MIX.2C_MIXAL list hello world programs] page.

External links

* [http://www-cs-faculty.stanford.edu/~knuth/mmix.html MMIX 2009: A RISC Computer for the Third Millennium] Knuth's official MIX page
* [http://www-cs-faculty.stanford.edu/~knuth/mmix-news.html MMIX News] Knuth's official MIX news
* [http://www-cs-faculty.stanford.edu/~knuth/mmixware.html MMIXware: A RISC Computer for the Third Millennium] Knuth's official MIX book
* [http://dmoz.org/Computers/Programming/Languages/Assembly/MIX-MMIX Open Directory: Computers: Programming: Languages: Assembly: MIX-MMIX] many MIX-MMIX/MIXAL-MMIXAL links
* [http://search.cpan.org/perldoc?Hardware::Simulator::MIX Hardware::Simulator::MIX] Perl module from CPAN


Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?
Synonyms:

Look at other dictionaries:

  • -mix — mix·is; …   English syllables

  • Mix FM — is a radio name and format. It is given to certain radio stations around the world with that name, while having the mix format. Although some stations don t have the name Mix FM , they can still have the format of Mixed Hits a variety of… …   Wikipedia

  • mix — [mɪks] noun [countable usually singular] a group of different things combined together for a particular purpose: • If the investment manager picks the right mix of bonds, his total return should rise quickly. ˈasset ˌmix FINANCE a mix of… …   Financial and business terms

  • Mix — Mix, mixes, mixture or mixing may refer to: Contents 1 Science and mathematics 2 Music and radio 3 People …   Wikipedia

  • MIX (XM) — MIX Broadcast area Off Air branding = Today s Mix Slogan The Best Variety of the 80s, 90s, and Now! Frequency XM 12 First air date …   Wikipedia

  • MIX — ist ein fiktiver, idealer Computer, welchen Donald E. Knuth in seinem Buch The Art of Computer Programming zur Illustration von Algorithmen nutzt. Der MIX Modellcomputer wird später durch den MMIX, eine moderne und erweiterte Version, ersetzt.… …   Deutsch Wikipedia

  • mix — mix·ite; mix·ol·o·gist; mix·ol·o·gy; mix·tec; mix·te·can; mix·ture; neph·ro·mix·i·um; pan·mix·ia; poly·mix·ia; pseu·do·mix·is; un·mix; ver·mix; ad·mix; mix·tie max·tie; pre·mix; re·mix; cac·o·mix·le; mix·able·ness; mix·te·ca; mix·te·co; mix·ter… …   English syllables

  • MIX — MIX  это гипотетический компьютер, использованный в монографии Дональда Кнута, «Искусство программирования»[1]. Номер модели компьютера MIX  1009, происходит от комбинации номеров и названий коммерческих моделей машин, современных… …   Википедия

  • Mix 94.5 — FM Broadcast area Perth Frequency 1210 kHz AM (1941–1978) 1206 kHz AM (1978–1991) 94.5 MHz FM (1991–) First air date …   Wikipedia

  • mix — [miks] vt. [prob. back form. < mixt, mixed, taken as pp. < Fr mixte < L mixtus, pp. of miscere, to mix (> OE miscian) < IE base * meik > Gr meignynai, Welsh mysgu, to mix] 1. to put or blend together in a single mass, collection …   English World dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”