TArntsen: Corrected, extended, reference added

2016-05-25T05:21:09Z

Corrected, extended, reference added

← Older revision		Revision as of 05:21, 25 May 2016
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	'''Norsk Data 48-bit ~~single precision~~ format:'''		'''Norsk Data 48-bit floating point format:'''
	{\|
	\|-		The [[NORD-10]] and the [[ND-100]] could use two different hardware floating point formats, either the 48-bit format described on this page, or alternatively ordered with [[32-bit floating point]] hardware.
	\| bit ~~47 \|\| (1~~ bit) \|~~\| Sign~~ bit
	\|-		The [[ND-500]] and [[ND-5000 family\|ND-5000]] used only the [[32-bit floating point]] format for single precision, and [[64-bit floating point]] as double precision. The ND-100 (or -110, -120) front ends in those systems would normally have come with the 32-bit option in order to be compatible with their 500(0) companion. The 48-bit format described on this page is only used by the 16-bit ND computers.
	\| bit 46-~~32 \|\|~~ (~~15 bits~~) ~~\|\| Exponent~~
	\|-
	\| bit ~~31-~~0 ~~\|\| (32 bits~~) ~~\|\| Mantissa~~
	\|-
	\|}
	~~Exponent has a bias of +256~~. ~~(Subtract 256 to get true exponent)~~

	~~'''Special values for exponent:'''~~		{\|class="wikitable"
	{\|		!Field !! #Bits !! Purpose
	\|-		\|-
	\| ~~''All bits zero except sign~~ bit~~'':~~ \|\| ~~'''Floating underflow'''.~~		\|bit 47 \|\| 1 \|\| Sign bit
	\|-		\|-
	\| ~~''0 (binary 0, aka 0x00)'':~~ \|\| ~~'''Zero'''~~		\|bit 46-32 \|\| 15 \|\| Exponent
	\|-		\|-
			\| bit 31-0 \|\| 32 \|\| Mantissa
	\|}		\|}

	~~Mantissa~~ has an implicit ~~33th~~ bit of 1 (~~unless mantissa~~ is 0).		* The mantissa is normalized: 0.5 ≤ ''mantissa'' < 1
	~~This is the 0.5 bit~~, i.e. ~~mantissa is normalised to be 0.5 < mantissa < 1~~.0		* The mantissa has no implicit bit, unlike the [[32-bit floating point\|32-bit]] and [[64-bit floating point\|64-bit]] formats
			* The decimal point is thus to the left of the 32th bit (before exponent is applied)
			* The exponent has a bias of 2<sup>14</sup>, or 16384 (subtract 16384 to get true exponent)

			'''Special values'''
			* All 48 bits zero: '''Zero.'''
			* ''(Any special value (e.g. -0) reprecenting floating point underflow is not documented in the ND-100 reference manual)

			'''Precision'''
			* 32 bits or approximately 10 decimal digits

	~~Decimal point is thus to the left of the implicit 33th bit~~.		'''Range'''
			* 2<sup>-16384</sup> - 0.5 ≤ X < 2<sup>16383</sup> - 1 or X = 0
			or
			* approximately 10<sup>-4920</sup> < X < 10<sup>4920</sup>

	~~The 48-bit floating point format is only used by the 16-bit~~ ND ~~computers, the 32~~-~~bit computers used the [[32-bit_floating_point~~\|~~32-bit format]] as its single precision format~~.		=== Sources ===
			* {{ND-doc\|06.014.02}}

TArntsen: Initial 48-bit floating point page

2013-04-04T14:23:44Z

Initial 48-bit floating point page

New page

'''Norsk Data 48-bit single precision format:'''
{|
|-
| bit 47 || (1 bit) || Sign bit
|-
| bit 46-32 || (15 bits) || Exponent
|-
| bit 31-0 || (32 bits) || Mantissa
|-
|}
Exponent has a bias of +256. (Subtract 256 to get true exponent)

'''Special values for exponent:'''
{|
|-
| ''All bits zero except sign bit'': || '''Floating underflow'''.
|-
| ''0 (binary 0, aka 0x00)'': || '''Zero'''
|-
|}

Mantissa has an implicit 33th bit of 1 (unless mantissa is 0).
This is the 0.5 bit, i.e. mantissa is normalised to be 0.5 < mantissa < 1.0

Decimal point is thus to the left of the implicit 33th bit.

The 48-bit floating point format is only used by the 16-bit ND computers, the 32-bit computers used the [[32-bit_floating_point|32-bit format]] as its single precision format.

48-bit floating point - Revision history

TArntsen: Corrected, extended, reference added

TArntsen: Initial 48-bit floating point page