FDIV bug in Pentium chips!!!

Stuart Priest priest at yorvic.york.ac.uk
Thu Dec 8 07:07:15 EST 1994

In article <3bo1qf$3j2 at news.iastate.edu>, kurtg at iastate.edu (Kurt R Glaesemann) writes:
|> In article <3bl9af$jlp at xap.xyplex.com>,  <dlaskey at xyplex.com> wrote:
|> >By the way...If you do any serious number crunching and use 256 in your 
|> >calculations such as cell A1 (4195835 * 256)
|> >                     cell A2 (3145727 / 256)
|> >		     cell A3  =a1/a2
|> >You are boned.  The Pentium will give the result 87407.92362
|> >Acual answer is 				 87413.2569
|> >
|> >Hmmmmmm The error is to the LEFT of the decimal point.  These Chips Suck!
|> You really didn't need more than three significant figures  ;-)
|> >Have fun doing taxes...remember calculations done on a Pentium are still your 
|> >responsibility.  You will be liable for all interest and penalties!
|> I wonder if water comes out linear using quantum mechanics programs on
|> pentiums.  :-( 
|> -- 
|> kurtg at iastate.edu
(For those of you not up on the latest.... a bug was found in the
 Pentium's math coprocessor a week ago.  Intel acknowledged that it knew
 about it for a long time.)


Q:  How many Pentium designers does it take to screw in a light bulb?
A:  1.99904274017, but that's close enough for non-technical people.

Q:  What do you get when you cross a Pentium PC with a  research grant?
A:  A mad scientist.

Q:  What's another name for the "Intel Inside" sticker they put on
A:  The warning label.

Q:  What do you call a series of FDIV instructions on a Pentium?
A:  Successive approximations.

Q:  Complete the following word analogy:  Add is to Subtract as Multiply
    is to:
        1)  Divide
        2)  ROUND
        3)  RANDOM
        4)  On a Pentium, all of the above
A:  Number 4.

Q:  What algorithm did Intel use in the Pentium's floating point divider?
A:  "Life is like a box of chocolates." (Source: F. Gump of Intel)

Q:  Why didn't Intel call the Pentium the 586?
A:  Because they added 486 and 100 on the first Pentium and got

Q:  According to Intel, the Pentium conforms to the IEEE standards 754
    and 854 for floating point arithmetic.  If you fly in aircraft
    designed using a Pentium, what is the correct pronunciation of "IEEE"?
A:  Aaaaaaaiiiiiiiiieeeeeeeeeeeee!

- --------------------------------------------------------------------------

  9.9999973251   It's a FLAW, Dammit, not a Bug
  8.9999163362   It's Close Enough, We Say So
  7.9999414610   Nearly 300 Correct Opcodes
  6.9999831538   You Don't Need to Know What's Inside
  5.9999835137   Redefining the PC -- and Mathematics As Well
  4.9999999021   We Fixed It, Really
  3.9998245917   Division Considered Harmful
  2.9991523619   Why Do You Think They Call It *Floating* Point?
  1.9999103517   We're Looking for a Few Good Flaws
  0.9999999998   The Errata Inside

                                (o  o)
 | Stuart Priest, Computer Manager       priest at yorvic.york.ac.uk        |
 | Protein Structure Group         http://www.yorvic.york.ac.uk/~priest/ |
 ! Department of Chemistry                                               |
 | University of York               Telephone : 44 1904 432592           |
 | Heslington, York YO1 5DD, U.K.         Fax : 44 1904 410519           |
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