資料來源 : pyDict

護身符

資料來源 : Webster's Revised Unabridged Dictionary (1913)

Amulet \Am"u*let\, n. [L. amuletum: cf. F. amulette.]
   An ornament, gem, or scroll, or a package containing a relic,
   etc., worn as a charm or preservative against evils or
   mischief, such as diseases and witchcraft, and generally
   inscribed with mystic forms or characters.

   Note: [Also used figuratively.]

資料來源 : WordNet®

amulet
     n : a trinket or piece of jewelry thought to be a protection
         against evil [syn: {talisman}]

資料來源 : Free On-Line Dictionary of Computing

Amulet
     
         An implementation or the {Advanced RISC Machine}
        {microprocessor} architecture using the {micropipeline} design
        style.  In April 1994 the Amulet group in the Computer Science
        department of {Manchester University} took delivery of the
        AMULET1 {microprocessor}.  This was their first large scale
        asynchronous circuit and the world's first implementation of a
        commercial microprocessor architecture (ARM) in {asynchronous
        logic}.
     
        Work was begun at the end of 1990 and the design despatched
        for fabrication in February 1993.  The primary intent was to
        demonstrate that an asynchronous microprocessor can consume
        less power than a synchronous design.
     
        The design incorporates a number of concurrent units which
        cooperate to give instruction level compatibility with the
        existing synchronous part.  These include an Address unit,
        which autonomously generates instruction fetch requests and
        interleaves ({nondeterministic}ally) data requests from the
        Execution unit; a {Register} file which supplies operands,
        queues write destinations and handles data dependencies; an
        Execution unit which includes a multiplier, a shifter and an
        {ALU} with data-dependent delay; a Data interface which
        performs byte extraction and alignment and includes an
        {instruction prefetch} buffer, and a control path which
        performs {instruction decode}.  These units only synchronise
        to exchange data.
     
        The design demonstrates that all the usual problems of
        processor design can be solved in this asynchronous framework:
        backward {instruction set} compatibility, {interrupts} and
        exact {exceptions} for {memory faults} are all covered.  It
        also demonstrates some unusual behaviour, for instance
        {nondeterministic} prefetch depth beyond a branch instruction
        (though the instructions which actually get executed are, of
        course, deterministic).  There are some unusual problems for
        {compiler} {optimisation}, as the metric which must be used to
        compare alternative code sequences is continuous rather than
        discrete, and the {nondeterminism} in external behaviour must
        also be taken into account.
     
        The chip was designed using a mixture of custom {datapath} and
        compiled control logic elements, as was the synchronous ARM.
        The fabrication technology is the same as that used for one
        version of the synchronous part, reducing the number of
        variables when comparing the two parts.
     
        Two silicon implementations have been received and preliminary
        measurements have been taken from these.  The first is a 0.7um
        process and has achieved about 28 kDhrystones running the
        standard {benchmark} program.  The other is a 1 um
        implementation and achieves about 20 kDhrystones.  For the
        faster of the parts this is equivalent to a synchronous {ARM6}
        clocked at around 20MHz; in the case of AMULET1 it is likely
        that this speed is limited by the memory system cycle time
        (just over 50ns) rather than the processor chip itself.
     
        A fair comparison of devices at the same geometries gives the
        AMULET1 performance as about 70% of that of an {ARM6} running
        at 20MHz.  Its power consumption is very similar to that of
        the ARM6; the AMULET1 therefore delivers about 80 MIPS/W
        (compared with around 120 from a 20MHz ARM6).  Multiplication
        is several times faster on the AMULET1 owing to the inclusion
        of a specialised asynchronous multiplier.  This performance is
        reasonable considering that the AMULET1 is a first generation
        part, whereas the synchronous ARM has undergone several design
        iterations.  AMULET2 (currently under development) is expected
        to be three times faster than AMULET1 - 120 k{dhrystones} -
        and use less power.
     
        The {macrocell} size (without {pad ring}) is 5.5 mm by 4.5 mm
        on a 1 micron {CMOS} process, which is about twice the area of
        the synchronous part.  Some of the increase can be attributed
        to the more sophisticated organisation of the new part: it has
        a deeper {pipeline} than the clocked version and it supports
        multiple outstanding memory requests; there is also
        specialised circuitry to increase the multiplication speed.
        Although there is undoubtedly some overhead attributable to
        the asynchronous control logic, this is estimated to be closer
        to 20% than to the 100% suggested by the direct comparison.
     
        AMULET1 is code compatible with {ARM6} and is so is capable of
        running existing {binaries} without modification.  The
        implementation also includes features such as interrupts and
        memory aborts.
     
        The work was part of a broad {ESPRIT} funded investigation
        into low-power technologies within the European {Open
        Microprocessor systems Initiative} (OMI) programme, where
        there is interest in low-power techniques both for portable
        equipment and (in the longer term) to alleviate the problems
        of the increasingly high dissipation of high-performance
        chips.  This initial investigation into the role {asynchronous
        logic} might play has now demonstrated that asynchronous
        techniques can be applied to problems of the scale of a
        complete {microprocessor}.
     
        {Home (http://www.cs.man.ac.uk/amulet)}.
     
        (1994-12-08)