IIRC, the 68040 uP from Motorola (now Freescale) had an extended
format, too... at least for the "real" 68040 (not the LC040).
On Jul 28, 2006, at 12:45 PM, Joseph wrote:
If I recall correctly the intel chip has an "extended precision"
format that
uses 80 bits when doing calculation. These are used during calculation
regardless of the original floating point format. So if the values in
the
calculation are single precision (one's compliment 24 bit mantissa
with an 8
bit exponent) the full 80 bits are used as 'guard bits' to increase the
precision of the calculation. Of course the result is then truncated
to
single precision. In High Level Assembly (Randall Hyde's interesting
fusion
of assembly and high level language constructs) you can declare an 80
bit
value.
~joe
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Peter K.
Stys
Sent: Friday, July 28, 2006 11:36 AM
To: REALbasic NUG
Subject: Re: Re: Math Error?
Actually we're both right and wrong:
In[55]:=RealDigits[0.036,2,100]
Out[55]={{1,0,0,1,0,0,1,1,0,1,1,1,0,1,0,0,1,0,1,1,1,1,0,0,0,1,1,0,1,0,1
,0,0,
1,1,1,1,
1,1,0,1,1,1,1,1,0,0,1,1,1,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},-4}
Shows that 0.036 can be represented exactly in binary, but requires 51
significant digits (if I counted correctly to the last 1). So with a
64 bit double, it probably just missed the # of digits in the mantissa
to represent 0.036 exactly.
Nuf time wasted on this, just a curiosity.
P.
--
-----------------------------------------------------------------------
-----
---
Peter K. Stys, MD
Professor of Medicine(Neurology), Senior Scientist
Ottawa Health Research Institute, Div. of Neuroscience
Ottawa Hospital / University of Ottawa
Ontario, CANADA
tel: (613)761-5444
fax: (613)761-5330
http://www.ohri.ca/profiles/stys.asp
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