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/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).
This article is provided by FOLDOC - Free Online Dictionary of Computing (
References in periodicals archive ?
About the stage name: One, perhaps apocryphal, story has it that Richard Melville Hall's parents gave it him, to reference the family's lineal descent from Melville the author.
Moby, whose legal name is Richard Melville Hall, rose to fame in the 1990s for his electronic dance music, including the 1999 electronica album Play .
Moby, real name Richard Melville Hall, said: "I moved to LA because New York has become a sadly affluent THE how his THE how his Daily Record place similar to London.
American performer Richard Melville Hall (aka Moby) will be in Lebanon for a one-night stand to perform the greatest of his commercial fare.
The US act - singer Richard Melville Hall - will top the bill on Stage Two at Balado, with Beth Orton and Morcheeba.
MOBy DestroyeD Electro soundscapery from Richard Melville Hall. Tenth album includes epic single The Day.
Born Richard Melville Hall, it was inevitable he would acquire the nickname Moby.
The 36-year-old musician - real name Richard Melville Hall - says he tried illegal substances to impress his classmates.
Meanwhile, Moby - real name Richard Melville Hall - remains a committed Christian and vegan, though his religious beliefs are far from fundamentalist.
New Yorker Moby, real name Richard Melville Hall, was propelled into pop's premier league two years ago when his record-breaking album Play became a worldwide smash.