Power CD-ROM!! 8/Power CD-ROM 8.iso/docs/intel.txt

Text File | 1994-12-14 | 13.2 KB | 229 lines

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¬      Intel Pentium(TM) Processor: Floating Point Unit Information        ¬
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FLOATING POINT FLAW IN THE PENTIUM PROCESSOR

   Overview
   Earlier this year, as a part of Intel's ongoing testing and product
   development work, a flaw was discovered in the floating point unit (FPU)
   of the Pentium processor.  This flaw affects the accuracy of the
   floating point divide instruction for certain combinations of input
   operands (i.e. certain combinations of specific numbers). The impact of
   the flaw is that for one in nine billion possible independent divides,
   the precision of the result is reduced. The flaw can occur in all three
   (single, double, and extended) precisions, and is independent of
   rounding mode.  The flaw was detected during the course of over seven
   trillion divisions of testing that have been performed on the Pentium
   processor, and a detailed investigation has determined the cause.

   Description
   For certain rare divisions (approximately one in nine billion divide
   pairs), the result of a floating point divide is returned with reduced
   precision.  The flaw is due to a problem with the lookup table used by
   the iterative algorithm that performs the divide instruction. There is
   no simple characterization of the values for which this flaw occurs.
   However, Intel has run trillions of different random divides to validate
   that the occurrence is less than one in nine billion: the precision of
   the result ranges from the 4th to the 19th significant digit (or the 4th
   to the 19th place after the decimal point in numbers expressed in
   scientific notation, an example of which is 0.12345 x 10e5).
   Statistically, for these values, the 4th significant digit is the least
   likely position for an error.  Importantly, intensive testing has shown
   that no known physical constant causes the reduced precision.

   Types of Applications Analyzed
   The impact of the flaw varies by the rate of use of floating point
   instructions,  the input data fed to them, the use of the results in
   further computations, and the needed accuracy of the application.  Intel
   has assessed the likely impact of the flaw on three types of
   applications that might be run on a Pentium processor-based system.
   These include: (i) commercial PC applications on desktop and mobile
   platforms running MS-DOS*, Windows*, and OS/2*. This class includes
   basic spreadsheets and accounting applications and personal finance;
   (ii) technical and workstation applications, such as engineering and
   scientific, advanced multimedia, educational and financial applications
   (thus this class includes "power users" of spreadsheets such as
   financial analysts and financial engineers); and (iii) server and
   transaction processing applications.

   Commercial PC Applications
   These applications were addressed by extensive internal validation and
   surveying external experts. A large majority of these applications do
   not invoke the floating point unit at all, much less floating point
   divides. This includes applications such as word processing, text
   editing and e-mail. In the commercial PC domain, the majority of
   applications that do use floating point do not invoke an appreciable
   number of different divides and hence do not introduce meaningful
   failures that will pose a data integrity problem during the useful life
   of the part. For applications such as corporate financial analysis and

   forecasting, marketing analysis, planning and so forth, the likelihood
   of encountering reduced precision divides is low. This is because
   typical calculations here are dominated by comparisons and additions.
   The input-output operations and the time for human conception of the
   results consume orders of magnitude more time than the processor spends
   performing arithmetic operations. This effect limits the number of
   divisions that are computed per day to well below what is necessary to
   have any appreciable probability of experiencing a meaningful
   inaccuracy. As an example, consider a large budget calculation
   implemented as a 700x700 cell spreadsheet, which is run an average of a
   few times a day. This will produce fewer than 10,000 divisions a day (on
   average): so few divisions that no reduced precision is likely to be
   seen for thousands of years. A more typical spreadsheet user doing 1000
   divides per day will encounter this reduced precision once in every
   27,000 years of use.

   Technical/Workstation Applications
   The second class of applications studied were workstation applications,
   broken down further: scientific/engineering and financial.  Scientific
   and engineering applications were studied extensively using leading
   vendors' analysis and simulation packages.  These applications, such as
   structural mechanics, fluid mechanics, computational biology, chemistry,
   and mathematics, were studied to determine the numerical effects of the
   reduced precision.  For structural mechanics -- among the worst problems
   for numerical convergence -- an error in the fourth significant digit
   would appear no more often than once every thousand years.  Many other
   applications that iterate to convergence, such as circuit simulation,
   are even less susceptible to reduced precision due to the algorithms
   they employ.  The average over a large range of applications was an
   expected meaningful error rate of less than one per thousand years.
   Particular technical applications employing unusually large numbers of
   divides and requiring extra precision need to be evaluated individually.

   Many workstation financial applications perform a significant number of
   divides, but the impact of the reduced precision is likely to be low,
   varying with the likelihood of its  propagation.  The typical financial
   user will not likely see a meaningful error in the usable life of the
   machine. In fact, the likelihood is less than one error per 270 years of
   use.

   However, as the most intensive floating point use is in this category
   and these are the applications which could possibly suffer meaningful
   error, users of these applications should contact Intel for more
   information.

   Server Applications
   Database and file server applications typically do essentially no
   floating point computations and thus are unffected by the flaw.

   Conclusions
   There is a flaw in the precision of the floating point divide operation
   of the Pentium processor.  The impact of the flaw varies by the rate of
   use of floating point instructions,  the input data fed to them, the use
   of the results in further computations, and the needed accuracy of the
   application.  The flaw is not meaningful for the vast majority of
   commercial PC applications.  The flaw is not likely to be meaningful

   over the usable life of the processor for the remainder of these
   commercial applications and most workstation applications.  Some
   workstation applications may see occasional reduced precision results
   from the flaw.  The flaw has no effect on server applications.

   Intel will work with users of applications involving intensive floating
   point calculations and resolve their concerns in the appropriate
   fashion, including, if necessary, replacing their chips. Please call
   Intel at 1-800-628-8686 (international: 916-356-3551) if you have
   concerns or need more information relating to this issue.


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     INTEL CORPORATION INTRODUCES 90 AND 100 MHz PENTIUM(TM) PROCESSORS


     SANTA CLARA, Calif., March 7, 1994 -- Intel Corporation today
     introduced new Pentium(TM) processors running at frequencies of
     90 and 100 MHz.  The 100-MHz version of the Pentium processor
     runs today's PC software faster than any other processor
     available.  It is 50 percent faster than the original version
     announced one year ago and has an iCOMP(TM) index rating of 815
     with a SPECint92 rating of 100.0.
     These new Pentium processors will be manufactured in
     volume at Intel's most advanced microprocessor production
     factories in Ireland and Santa Clara.  With the 3.3 volt,
     0.6 micron, 4-layer metal advanced process technology, the chip
     is approximately half the size of other members of the Pentium
     processor family.  This announcement comes on the heels of
     demonstrating a 150-MHz Pentium processor at the IEEE International
     Solid State Circuits Conference (ISSCC) in San Francisco
     approximately two weeks ago.
     "These new products arrive as Pentium processor-based PC's
     are moving rapidly through all channels, including retail, with
     aggressive price points for today's performance-oriented
     applications," said Paul Otellini, senior vice president and
     general manager of Intel's microprocessor product group.  "PC
     purchasers can now buy Intel's fastest processor for today's and
     tomorrow's application at very affordable prices.  This will
     accelerate Pentium processors entering all market segments,
     including the home, at a rate faster than any previous processor."


The New Pentium Processors
     The 90-MHz version of the Pentium processor has an iCOMP
     index of 735 and a SPECint92 rating of 90.0.  Both the 90- and
     100-MHz versions achieve SPECint92 ratings higher than any other
     mass market processor selling today or promised for delivery this
     year.
     The new 90- and 100-MHz processors have a typical power
     dissipation of 4.0 watts or less.  Extra features for easier system
     design and multiprocessing have been added such as the Intel advanced
     programmable interrupt controller (APIC), enabling dual processing
     systems at PC price points.
     PCs and servers based on the new chips are expected to be
     announced within the next 60 days from many manufacturers.
     Integrated SL technology will enable Pentium processor-based
     notebook computers with robust power management to be on the market
     later this year.

World's Fastest 486
     A 100 MHz IntelDX4(TM) processor, with an iCOMP index rating of
     435, also was announced today.  A 75-MHz version is also available
     (iCOMP index rating of 319).  The 100-MHz version has a SPECint92
     rating of 51.4.  The IntelDX4 processor offers up to 50 percent
     more performance than the IntelDX2TM processor.
     "The world's best performing notebooks are based on the
     IntelDX4 processor," said Otellini.  "Mobile computer users can get
     the same level of performance as desktop users without compromising
     battery life."
     System manufacturers can use current Intel486(TM) processor
     system designs with minor modifications to benefit from the IntelDX4
     processor's additional performance. Besides the benefits of 3.3 volt
     design for low-power operation, the processor is enhanced with SL
     technology for long battery life notebooks and energy-efficient
     desktops.  The IntelDX4 processor has twice the amount of on-chip
     cache (16 kilobytes) as the IntelDX2(TM) microprocessor.

PCI Local Bus
     Intel also introduced the PCI chip set for local bus support for
     the 90- and 100- MHz Pentium processors.  The 82430NX PCIset allows
     system manufacturers to build the highest performance desktop
     systems based on the Pentium processor and PCI.  The architecture
     of the 82430NX PCIset provides options for multiple system
     configurations to target different price points.  The PCIset also
     takes advantage of the fast performance and plug-and-play
     capabilities of the PCI local bus to support high-performance
     graphics, networking, disk drives and multimedia.

Pricing and Availability
     The new versions of the Pentium and the IntelDX4 processors are
     available now. The 90-MHz version of the Pentium processor is
     priced at $849 each in 1,000-piece quantities.  The 100-MHz
     version is $995 each in 1,000-piece quantities and is available
     now in limited volumes and moving to high volumes in Q4 1994.
     The 75-MHz IntelDX4 processor is $475 while the 100-MHz IntelDX4
     processor is $580 each in 1,000-piece quantities (Q2 pricing).
     For pricing and availability outside the United States, contact
     the regional Intel sales office.
     For additional information about these new processors or
     other Intel products, contact an Intel sales representative or
     call [phone].  For literature, contact the Literature Center
     at [phone] in the U.S. and Canada, or write to:  Intel
     Literature, P.O. Box 7620, Mt. Prospect, IL 60056-7620.
     Intel, the world's largest chip maker, is also a leading
     manufacturer of personal computer networking and communications
     products.