taocp

** MIX 1009 computer from Donald Knuth's /The Art of Computer Programming/

** Simulator

The ~mix~ simulator faithfully mimics the third edition's hypothetical computer in all its aspects, including a full complement of attached I/O devices, as described in Section 1.3.1: disks, drums, magnetic and paper tapes, a printer, a card reader, a card punch and a teletype (console). Each device is backed by a file, or by standard input/output for the console. The latencies of the devices are accounted for when calculating execution times, and based upon what might have been expected in the era of the book's first publication.

Normally upon starting, the simulator will immediately boot MIX, and continue to run until a ~HLT~ instruction is executed. It will then quit. However if the ~-op~ argument is given, the simulator will prompt the "operator" to press the computer's GO button before booting commences, and prompt again on whether to resume execution following the ~HLT~, or quit.

** Assembler

The ~mixal~ assembler reads from the program file (encoded as UTF-8) given as an argument, or from standard input if ~-~ is given, and outputs simulated punched cards for the card reader, containing the translated object code. The MIX simulator loads the object code from the card reader and runs until a ~HLT~ instruction or error condition is encountered. (Loading of object code from the reader is achieved by prepending a "loader" card, as described in Exercise 26 of Section 1.3.1.)

Note that this unforgiving implementation of the assembler requires the input file conform to the MIXAL format as described by the book, eg. no tabs or other non-MIX characters are allowed, instruction fields span columns 1-10, 12-15, 17-80, etc. The included ~mixal-fmt~ shell script can correct most formatting errors.

** Supervisor

The interrupt facility and supervisor mode for the expanded computer, described in Exercise 18, Section 1.4.4, can be enabled by giving the ~-irq~ argument to ~mix~ and ~mixal~, or by setting the environment variable ~MIX_ENABLE_INTERRUPTS=y~. A program using this feature, and other programs of interest, can be found in the examples directory.

** Walkthrough

: $ go test ./... : ? github.com/jflude/taocp/cmd/mix [no test files] : ? github.com/jflude/taocp/cmd/mixal [no test files] : ok github.com/jflude/taocp/mix 0.444s : ok github.com/jflude/taocp/mixal 0.168s : $ go install ./... : $ mixal : error: mixal [-irq] INPUT-FILE : $ mix -help : Usage of mix: : -boot int : unit to boot from (default 16) : -d10 string : (default "drum10.mix") : -d11 string : (default "drum11.mix") : -d12 string : (default "disc12.mix") : -d13 string : (default "disc13.mix") : -d14 string : (default "disc14.mix") : -d15 string : (default "disc15.mix") : -d8 string : (default "drum08.mix") : -d9 string : (default "drum09.mix") : -irq : enable interrupts : -op : involve the operator : -pap string : (default "paper.mix") : -prt string : (default "printer.mix") : -pun string : (default "punch.mix") : -rdr string : (default "reader.mix") : -t0 string : (default "tape00.mix") : -t1 string : (default "tape01.mix") : -t2 string : (default "tape02.mix") : -t3 string : (default "tape03.mix") : -t4 string : (default "tape04.mix") : -t5 string : (default "tape05.mix") : -t6 string : (default "tape06.mix") : -t7 string : (default "tape07.mix") : -floor int : don't trace addresses below this (default 32) : -trace string : output trace to file : -tty string : : $ mixal examples/500primes.mixal : $ ls -l *.mix : -rw-r--r-- 1 justin staff 972 Jan 1 00:00 reader.mix : $ mix : mix: halted at 3029: HLT (elapsed: 6762025u, idle: 5969153u) : $ ls -l *.mix : -rw-r--r-- 1 justin staff 2777 Jan 1 00:00 printer.mix : -rw-r--r-- 1 justin staff 972 Jan 1 00:00 reader.mix : $ head -5 printer.mix : : FIRST FIVE HUNDRED PRIMES : 0002 0233 0547 0877 1229 1597 1993 2371 2749 3187 : 0003 0239 0557 0881 1231 1601 1997 2377 2753 3191 : 0005 0241 0563 0883 1237 1607 1999 2381 2767 3203 : 0007 0251 0569 0887 1249 1609 2003 2383 2777 3209

** Sandbox

As a convenience, the ~mix-run~ script, in a single operation, will reformat, assemble and execute its input file within a temporary sandbox, and output (or tail) an I/O device's backing file.

: $ cat examples/echo.mixal : * EXAMPLE: ECHO LINES ENTERED ON THE TELETYPE, UNTIL AN INITIAL PERIOD. : TTY EQU 19 : ORIG 1000 : OUTPUT OUT BUF(TTY) : START IN BUF(TTY) : JBUS *(TTY) : LDA BUF : CMPA PERIOD : JNE OUTPUT : HLT : PERIOD ALF . : END START : $ mix-run examples/echo.mixal : HELLO : HELLO : BYE : BYE : . : mix: halted at 1006: HLT (elapsed: 35240489u, idle: 14060000u)

** Tracing

~mix~ can write an execution trace to a file. Register contents are displayed in decimal and signed octal.

: $ mix -trace foo.out : mix: halted at 3029: HLT (elapsed: 6762025u, idle: 5969153u) : $ head -36 foo.out : : _______________________________________________________ : A: 0 (+00000000000) OP: 3000: IOC 0(18) : X: 8775582 (+00041363636) OV: N CI: = : I1: 0 (+00000000000) M : I2: 0 (+00000000000) 0: +00000005670 : I3: 3000 (+00000005670) 1: +00035002044 : I4: 0 (+00000000000) 2: +00000000011 : I5: 0 (+00000000000) 3: +00003002042 : I6: 0 (+00000000000) 4: +00036000510 : J: 13 (+00000000015) 5: +00001000006 : Device: ..................... : Idle! 60000u Elapsed: 661973u : : _______________________________________________________ : A: 0 (+00000000000) OP: 3001: LD1 2050 : X: 8775582 (+00041363636) OV: N CI: = : I1: 0 (+00000000000) M : I2: 0 (+00000000000) 2050: -00000000763 : I3: 3000 (+00000005670) 2051: +00000000003 : I4: 0 (+00000000000) 2052: +00000000000 : I5: 0 (+00000000000) 2053: +00000000000 : I6: 0 (+00000000000) 2054: +00000000000 : J: 13 (+00000000015) 2055: +00000000000 : Device! ..................P.. : Idle: 60000u Elapsed: 661974u : : _______________________________________________________ : A: 0 (+00000000000) OP: 3002: LD2 2051 : X: 8775582 (+00041363636) OV: N CI: = : I1: -499 (-00000000763) M : I2: 0 (+00000000000) 2051: +00000000003 : I3: 3000 (+00000005670) 2052: +00000000000 : I4: 0 (+00000000000) 2053: +00000000000 : I5: 0 (+00000000000) 2054: +00000000000 : I6: 0 (+00000000000) 2055: +00000000000 : J: 13 (+00000000015) 2056: +00000000000 : Device: ..................P.. : Idle: 60000u Elapsed: 661976u

** Resources

The [[https://exhibits.stanford.edu/stanford-pubs/catalog/xr254ff4308][guide]] for Knuth's implementation at Stanford, on the IBM S/360
The [[https://www.cs.utexas.edu/ftp/techreports/tr77-64.pdf][manual]] for UT Austin's implementation, on the CDC 6000
James L. Peterson's /[[http://www.jklp.org/profession/books/mix/index.html][Computer Organization & Assembly Language Programming]]/

Taocp

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