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Re: Floating Point Bug on Intel Pentium CPUs [message #3167 is a reply to message #3156]

Wed, 23 November 1994 11:19

murthy
Messages: 7
Registered: February 1994

Junior Member

Gregory D. Nowicki (nowicki@tardis.larc.nasa.gov) wrote:
: In article <3avsus$22n@spool.cs.wisc.edu>, Liam Gumley <liamg@ssec.wisc.edu> writes:
: >This is not strictly IDL related, but may affect IDL users on Pentium
: >platforms who run complicated models. Recent discussion in the
: >comp.sys.intel newsgroup has focussed on the discovery of a bug
: >in the floating point unit on Intel Pentium CPUs. The bug is evident
: >during divide operations. The following code reportedly will show the
: >bug. It should give zero (or near enough to it), but on the Pentium
: >it returns z = 256.
: >
: >x = 4195835.
: >y = 3145727.
: >z = x - (x/y)*y
: >
: >Apparently some kind of chip replacement strategy is being considered
: >by Intel. For more details, tune to comp.sys.intel
: >
: >Cheers,
: >Liam.
: >liamg@ssec.wisc.edu
: >

: Above problem only there if using DOUBLE precision math, (DOUBLE in IDL,
: real*8 in Fortran, double in C, etc.)

: -Greg

: /* Greg Nowicki | Mail Stop 401A | LIDAR Applications Group */
: /* NASA Langley Research Center | Hampton, Virginia 23681-0001 */
: /* Voice: (804) 864-2713 | FAX: (804) 864-7790 */
: /* nowicki@tardis.larc.nasa.gov | My opinions and mine alone . . . */

Not true. I get it using plain old FLOATs on my P90.

Jayant
--

Jayant Murthy murthy@pha.jhu.edu
410-516-7027

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[Message index]

		Re: Floating Point Bug on Intel Pentium CPUs By: nowicki on Fri, 25 November 1994 05:51
		Re: Floating Point Bug on Intel Pentium CPUs By: murthy on Wed, 23 November 1994 11:19
		Re: Floating Point Bug on Intel Pentium CPUs By: nowicki on Wed, 23 November 1994 10:43

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