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What does 8-bit / 16-bit actually refer to?

Some of the consoles I've owned are:

  • 8 bit NES
  • 16 bit Megadrive (Genesis)
  • 64 bit Nintendo 64

I've always been curious about what the number of bits specified actually means? I realise that when taking unsigned integers into account, the maximum value 8 bits is 255, 16 bits is 65,535, and 64 bits is9,223,372,036,854,775,807.

Does it refer to the amount of graphical data that can be transfered at any one time? Or the colour palette? Or the largest a numeric data-type can be? Or some other factors?

marked as duplicate by Grace Note Jun 15 '11 at 12:16

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migrated from superuser.com Jun 15 '11 at 0:11

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  • 1
    max 8-bit value is 255. – Dave DuPlantis Jun 15 '11 at 0:53
  • @Dave DuPlantis Doh! – aligray Jun 15 '11 at 1:14
  • OBOB ... it even gets you on SE sites! :) – Dave DuPlantis Jun 15 '11 at 1:34
  • @Dave What is OBOB? – aligray Jun 15 '11 at 1:36
  • Off By One Bug. It's typically seen in loops: going from 1 to n in a system where arrays start with 0 (and thus the loop should go to n-1), that kind of thing. Or here: 256 different unsigned ints can be expressed in 8 bits, they just start at 0. – Dave DuPlantis Jun 15 '11 at 1:43

It generally represents the size of the CPU registers and the main memory bandwidth. This equates to data processing abilities and is most commonly associated with the amount of memory that is addressable (see 32-bits and the 4GB memory limit). Registers can easily be combined to work with extra large numbers, and is not necessarily related to the graphics link or graphics memory bandwidth.


Pretty much the same thing it means with computers. Unless you're talking about the 24-bit Neo Geo.

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