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PENTIUM.PRS
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1993-12-20
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Åäìôêöî ÅæÄéäÆÆÄæ ╬╠╬╠╬╠╧╧╬╠╡
σΣα≤⌠±Σ α±≤ΦΓδΣ
│ The Pentium(TM) processor is
┌┐ │ the newest and most powerful
┌──┐┌──┐┌──┐│└┐ ┌┐┌┐┌┐┌─┬─┐ │ member of Intel's x86 family of
│┌┐││──││┌┐││┌┘ │││││││ │ │ microprocessors. While
│└┘││──┤│││││└─┐│││└┘││├─┤│ │ incorporating new features and
│┌─┘└──┘└┘└┘└──┘└┘└──┘└┘ └┘ │ improvements made possible by
└┘ ∩ ± ε Γ Σ ≥ ≥ ε ± │ advances in semiconductor
≤ Σ Γ τ φ Φ Γ α δ │ technology, the Pentium processor
ε ⌡ Σ ± ⌡ Φ Σ ÷ │ is 100% code compatible with
│ previous members of x86 family,
Γε∞∩δΦΣπ ß√ ≤εε±αΘ Σφα√α≤Φ │ preserving the value of invested
│ software.
│
" ≤τΣ á₧-ßΦ≤ πα≤α ß⌠≥ αδδε÷≥ ≤τΣ │ The Pentium processor
∩Σφ≤Φ⌠∞ ∩±εΓΣ≥≥ε± ≤ε ≤±αφ≥σΣ± │ incorporates a superscalar
πα≤α ≤ε αφπ σ±ε∞ ∞Σ∞ε±√ α≤ ±α≤Σ≥ │ architecture, improved floating
⌠∩ ≤ε ƒ£ó îß√≤Σ/≥ΣΓ, ≤τΣ ∩ΣαΩ │ point unit, separate on-chip code
≤±αφ≥σΣ± ±α≤Σ εσ ≤τΣ ƒÜ îçⁿ │ and write-back data caches, 64-
êφ≤Σδ₧óá is ¢áÜ îß√≤Σ/≥ΣΓ. " │ bit external data bus, and other
│ features designed to provide a
platform for high-performance │ instructions at once, one to each
computing. │ of the pipelines, in a process
│ known as "instruction pairing."
π⌠αδ Φφ≥≤±⌠Γ≤Φεφ ∩Φ∩ΣδΦφΣ≥ │ In this case, the instructions
│ must both be "simple", and the v-
The heart of the Pentium │ pipe always receives the next
processor is its superscalar │ sequential instruction after the
design, built around two │ one issued to the u-pipe. Each
instruction pipelines, each │ pipeline has its own ALU
capable of performing │ (arithmetic logic unit), address
independently. These pipelines │ generation circuitry, and
allow the Pentium processor to │ interface to the data cache.
execute two integer instructions │
in a single clock cycle, nearly │ ≥Σ∩α±α≤Σ ΓεπΣ αφπ πα≤α ΓαΓτΣ≥
doubling the chip's performance │
relative to an Intel486 chip at │ While the Intel486
the same frequency. │ microprocessor incorporated a
│ single 8 Kbyte cache, the Pentium
In many instances, the Pentium │ processor features two 8K caches,
processor can issue two │ one for instructions and one for
data. These caches act as │ processor's bus width (64 bits)
temporary storage places for │ with burst length (4 chunks.)
instructions and data obtained │
from slower, main memory; when a │ ß±αφΓτ ∩±ΣπΦΓ≤Φεφ
system uses data, it will likely │
use it again, and getting it from │ The Pentium processor also
an on-chip cache is much faster │ increases performance by using a
than getting it from main memory. │ small cache known as the Branch
│ Target Buffer (BTB) to provide
The Pentium processor's caches │ dynamic branch prediction. When
are 2-way set-associative caches, │ an instruction leads to a branch,
an improvement over simpler, │ the BTB "remembers" the
direct-mapped designs. They are │ instruction and the address of
organised with 32-byte lines, │ the branch taken. The BTB uses
which allows the cache circuitry │ this information to predict which
to search only 2 32-byte lines │ way the instruction will branch
rather than the entire cache. The │ the next time it is used, thereby
use of 32-byte lines (up from 16- │ saving time that would otherwise
byte lines on the 486 DX) is a │ be required to retrieve the
good match of the Pentium │ desired branch target. When the
BTB makes a correct prediction, │ ε≤τΣ± ∩Σ±σε±∞αφΓΣ Φ∞∩±ε⌡Σ∞Σφ≤≥
the branch is executed without │
delay, which enhances │ Internally, the Pentium
performance. │ processor uses a 32-bit bus, like
│ that of the Intel486. However,
Φ∞∩±ε⌡Σπ σδεα≤Φφµ ∩εΦφ≤ ⌠φΦ≤ │ the external data bus to memory
│ is 64-bits wide, doubling the
The floating point unit in the │ amount of data that may be
Pentium processor has been │ transferred in a single bus
completely redesigned over that │ cycle.
in the Intel486 microprocessor. │ The Pentium processor supports
It incorporates an 8-stage │ several types of bus cycles,
pipeline, which can execute one │ including burst mode, which loads
floating point operation every │ large (256-bit) portions of data
clock cycle. (In some instances, │ into the data cache in a single
it can execute two floating point │ bus cycle. The 64-bit data bus
operations per clock--when the │ allows the Pentium processor to
second instruction is an │ transfer data to and from memory
Exchange.) │ at rates up to 528 Mbyte/sec, a
│ more than 3-fold increase over
the peak transfer rate of the 50 │ a number of techniques to
MHz Intel486 (160 Mbyte/sec). │ maintain the integrity of the
│ data with which it is working.
Several instructions (such as │ Error detection is performed on
MOV and ALU operations) have been │ two levels: via parity checking
hardwired into the Pentium │ at the external pins; and
processor, which allows them to │ internally, on the on-chip memory
operate more quickly. In │ structures (cache, buffers, and
addition, numerous microcode │ microcode ROM.)
instructions execute more quickly │
due to the Pentium processor's │ For situations where data
dual pipelines. Finally, the │ integrity is especially crucial,
Pentium processor features an │ the Pentium processor supports
increased page size, which │ Functional Redundancy Checking
results in less page swapping in │ (FRC). FRC requires the use of
larger applications. │ two Pentium chips, one acting as
│ the master and the other as the
πα≤α Φφ≤Σµ±Φ≤√ │ "checker". The two chips run in
│ tandem, and the checker compares
The Pentium processor employs │ its output with that of the
master Pentium processor to │
assure that errors have not │
occurred. The use of FRC results │
in an error detection rate that │
is greater than 99 percent ñ │