/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').] 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 "The Meaning of `Hack'
"). 2. n. obs. The
maximum address space of a machine (see below). For a 6800 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 2) 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.
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 popular chips for which the term
could stand to be revived --- the Intel 8088 and 80286 with their
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