48-bit computing: Difference between revisions

Revision as of 22:55, 27 February 2019

Revision as of 22:25, 1 October 2019

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==Word size==

Computers with 48-bit [[Word (data type)|words]] include the [[AN/FSQ-32]], [[Control Data Corporation|CDC]] 1604/[[CDC 3000|upper-3000 series]], [[BESM#BESM-6|BESM-6]], [[Ferranti]] [[Atlas (computer)|Atlas]], and [[Burroughs large systems]].{{efn|The B5000, B5500 and B5700 took 3 bits in control words and numeric data for use as a tag; alphanumeric data and instruction syllables were stored in the full 48 bits and had no tags.}}{{efn|The B5900-B8xxx additionally had a 3- or 4-bit type tag.}}.

==Addressing==

The [[IBM System/38]] and the [[AS/400]], in its [[Complexcomplex instruction set computer|CISC]] variants, are 48-bit addressing systems. The address size used in [[logical block addressing]] was increased to 48 bits with the introduction of [[AT Attachment#ATA standards versions, transfer rates, and features|ATA-6]]. The [[Ext4]] file system physically limits the file block count to 48 bits.

The minimal implementation of the [[x86-64]] architecture provides 48-bit addressing encoded into 64 bits; future versions of the architecture can expand this without breaking properly written applications.

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==Images==

{{seeSee also|Deep color}}

In digital images, 48 bits per pixel, or 16 bits per each color channel (red, green and blue), is used for accurate processing. For the human eye, it is almost impossible to see any difference between such an image and a 24-bit image,{{Citation needed|date=June 2013}} but the existence of more shades of each of the three primary colors (65,536 as opposed to 256) means that more operations can be performed on the image without risk of noticeable [[Colour banding|banding]] or [[posterization]].