[1] : Jargon File (4.3.1, 29 Jun 2001)

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
   6802340 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.


see also:
appendix a bignum core brain-damaged 

[2] : The Free On-line Dictionary of Computing (27 SEP 03)

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 6802340 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
     
     
see also:
mit address space vax gigabytes bignum time-sharing 
address registers virtual memory core brain-damaged jargon file 

Moby >> M Words
Moby, definition of term: Moby
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