moby
 /moh'bee/

    [MIT: seems to have been in use among model railroad fans years ago.
    Derived from Melville's Moby Dick (some say from ?Moby Pickle?). Now
    common.]

    1. adj. Large, immense, complex, impressive. ?A Saturn V rocket is a truly
    moby frob.? ?Some MIT undergrads pulled off a moby hack at the Harvard-Yale
    game.? (See Appendix A for discussion.)

    2. n. obs. The maximum address space of a machine (see below). For a 680
    [234]0 or VAX or most modern 32-bit architectures, it is 4,294,967,296
    8-bit bytes (4 gigabytes).

    3. A title of address (never of third-person reference), usually used to
    show admiration, respect, and/or friendliness to a competent hacker. ?
    Greetings, moby Dave. How's that address-book thing for the Mac going??

    4. adj. In backgammon, doubles on the dice, as in moby sixes, moby ones,
    etc. Compare this with bignum (sense 3): double sixes are both bignums
    and moby sixes, but moby ones are not bignums (the use of moby to describe
    double ones is sarcastic). Standard emphatic forms: Moby foo, moby win,
    moby loss. Foby moo: a spoonerism due to Richard Greenblatt.

    5. The largest available unit of something which is available in discrete
    increments. Thus, ordering a ?moby Coke? at the local fast-food joint is
    not just a request for a large Coke, it's an explicit request for the
    largest size they sell.

    This term entered hackerdom with the Fabritek 256K memory added to the MIT
    AI PDP-6 machine, which was considered unimaginably huge when it was
    installed in the 1960s (at a time when a more typical memory size for a
    timesharing system was 72 kilobytes). Thus, a moby is classically 256K
    36-bit words, the size of a PDP-6 or PDP-10 moby. Back when address
    registers were narrow the term was more generally useful, because when a
    computer had virtual memory mapping, it might actually have more physical
    memory attached to it than any one program could access directly. One could
    then say ?This computer has 6 mobies? meaning that the ratio of physical
    memory to address space is 6, without having to say specifically how much
    memory there actually is. That in turn implied that the computer could
    timeshare six ?full-sized? programs without having to swap programs between
    memory and disk.

    Nowadays the low cost of processor logic means that address spaces are
    usually larger than the most physical memory you can cram onto a machine,
    so most systems have much less than one theoretical ?native? moby of core
    . Also, more modern memory-management techniques (esp. paging) make the
    ?moby count? less significant. However, there is one series of widely-used
    chips for which the term could stand to be revived ? the Intel 8088 and
    80286 with their incredibly brain-damaged segmented-memory designs. On
    these, a moby would be the 1-megabyte address span of a segment/offset pair
    (by coincidence, a PDP-10 moby was exactly 1 megabyte of 9-bit bytes).

moby

    /moh'bee/ (From MIT, seems to have been in use
   among model railroad fans years ago.  Derived from Melville's
   "Moby Dick", some say from "Moby Pickle") 1. Large, immense,
   complex, impressive.  "A Saturn V rocket is a truly moby
   frob."  "Some MIT undergrads pulled off a moby hack at the
   Harvard-Yale game."

   2. (Obsolete) The maximum address space of a computer (see
   below).  For a 680[234]0 or VAX or most modern 32-bit
   architectures, it is 4,294,967,296 8-bit bytes (four
   gigabytes).

   3. A title of address (never of third-person reference),
   usually used to show admiration, respect, and/or friendliness
   to a competent hacker.  "Greetings, moby Dave.  How's that
   address-book thing for the Mac going?"

   4. In backgammon, doubles on the dice, as in "moby sixes",
   "moby ones", etc.  Compare this with bignum: double sixes
   are both bignums and moby sixes, but moby ones are not bignums
   (the use of "moby" to describe double ones is sarcastic).

   5. The largest available unit of something which is available
   in discrete increments.  Thus a "moby Coke" is not just large,
   it's the largest size on sale.

   This term entered hackerdom with the Fabritek 256K memory
   added to the MIT AI PDP-6 machine, which was considered
   unimaginably huge when it was installed in the 1960s (at a
   time when a more typical memory size for a time-sharing
   system was 72 kilobytes).  Thus, a moby is classically 256K
   36-bit words, the size of a PDP-6 or PDP-10 moby.  Back when
   address registers were narrow the term was more generally
   useful, because when a computer had virtual memory mapping,
   it might actually have more physical memory attached to it
   than any one program could access directly.  One could then
   say "This computer has six mobies" meaning that the ratio of
   physical memory to address space is six, without having to say
   specifically how much memory there actually is.  That in turn
   implied that the computer could timeshare six "full-sized"
   programs without having to swap programs between memory and
   disk.

   Nowadays the low cost of processor logic means that address
   spaces are usually larger than the most physical memory you
   can cram onto a machine, so most systems have much *less* than
   one theoretical "native" moby of core.  Also, more modern
   memory-management techniques (especially paging) make the
   "moby count" less significant.  However, there is one series
   of widely-used chips for which the term could stand to be
   revived --- the Intel 8088 and 80286 with their incredibly
   brain-damaged segmented-memory designs.  On these, a "moby"
   would be the 1-megabyte address span of a segment/offset pair
   (by coincidence, a PDP-10 moby was exactly one megabyte of
   nine-bit bytes).

   [Jargon File]

   (1997-10-01)