Transcript AMD`s Microprocessors Architecture

 AMD’s Microprocessors Architecture
AMD’s
Microprocessor Model
I.
II.
III.
K5 (Four-Issue Out-of-order
Processor, first chip of K86 family)
K7 (Three-Issue SuperScalar
Processor)
Athlon (World’s First 7th Generation
x86 Processor)
Launce
Yr
Competitor
Intel Model
1994
100 MHz
Pentium
1998
Katmai
2000
Pentium III
Fields of discussion:
Basic features of each model’s architecture,
Instruction handling,
 Caches & Memory management,
Pipeline (# of stages, possible penalties).
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Part I: AMD’s K5
- Basic Features
- Advanced
four-issue superscalar core: that supports
speculative, out-of-order execution and register renaming.
- Die-sized static chip of 4.3 million transistors, 3.3-V designed,
implemented in AMD’s 0.5-micron, three-metal CMOS process.
- 30% Faster at Same Clock Rate as Pentium – (2.5 times as
fast as 486). K5: a flexible, aggressive microarchitecture that
achieves higher performance (on integer code, though less
emphasis is given on floating-point performance).
- The challenge of Decoding multiple x86 instructions in parallel
is achieved by predecoding them when fetched from memory
into the instruction cache.
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Block diagram of AMD’s K5
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K5 adds predecode bits to x86 instructions before caching them.
x86 instructions are converted into one or more microinstructions (RISCoperations or ROPs) – 16 bytes at a time - up to four ROPs issued per cycle.
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K5 ‘s instruction translation process
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Instructions are fed into a 16-byte queue,
Up to four ROPs worth of instructions can be pulled from queue during
each clock cycle,
Four identical ROP converters translate x86 instruction into ROPs.
A RISK-like outcome is acquired once past the ROP converters.
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K5 ‘s Execution Units
 ROPs are dispatched to Execution Units, in reservation stations, and wait
for the needed resources to become available.
Available Execution Units (6 in number) include:
 2 Dual ALUs (one with a shifter, the other with the divider – 2
execution stations)
 1 FPU (1 execution station)
 2 Dual Load/Store Units (2 execution stations each), and
 1 Branch Unit (2 execution stations).
 8 Operand Buses feed the Execution Units (4 units are fed with 2
operands on every cycle).
 5 Result Buses, 41 bits wide, support transfers on floating-point data (2
used in parallel to support x86 compatible floating-point operations).
 40-Word Register File
 1 16-entry reorder buffer (ROB), stores results from speculatively
executed instructions (and then results are written to register file).
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Pipeline in K5’s architecture
 6 stages of pipelining, only 5 of them affect performance – instruction timing.
 Requirement for an extra decode stage for the x86-to-ROP translation.
 Combination of address generation into the same stage as cache access.
Extra
decode
stage
2nd phase
1st phase
Calculation Full linear 32-bit
of cache address calculation,
segment-protection
index
checking
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Caches and Memory management
 The Data
Cache is
divided into
four banks.
There are 2
access ports
one for each
Load/Store
Unit.
 The Instruction Cache has a 16byte line size – a 16-byte buffer
ensures
compatibility
with
the
Pentium bus which performs 32-byte
bursts, so it
holds the
second
Cache line.
 The caches are virtually addressed and tagged to avoid the need to
translate addresses before a cache access.
 A single set of physical tags is shared by instruction and data caches.
Thus, conflicts with the CPU for cache access are eliminated and ensure
consistency between instruction and data caches
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Summarizing about AMD’s K5
 K5 goes further in combining x86 compatibility with RISC-like core,
(employing similar architecture as the NexGen’s Nx586)
achieving: - a large software base,
- high performance.
 K5 (at that time) competitors:
- Cyrix’s M1 (not yet launched in the market),
- Pentium
 holds large part of the marketplace, often forcing AMD to
provide higher performance at the same price,
 already on the way to increasing it’s clock rate (promising
to launch a 120-MHz speed rate (in 1 year’s time – early
1995), or even a 150-MHz speed rate (in 2 years time –
late 1995)).
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Part II: AMD’s K7 3-issue superscalar processor - Basic Features
10 stages of pipeline->
High clock rates
achievement,
Large L1 instruction data caches ->
Functions in systems
with of without
backside L2,
Astonishingly small
(184mm2), despite
transistor complexity
(22-million).
Up to 72 instructions can be in execution in K7’s out of order integer pipe,
floating-point pipe, and load/store unit.
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K7’s deep 10-stage pipeline
 Long pipeline (1st half occupied for x86 instruction decoding),
 Simple branch prediction by a 2.048-entry branch history
table with a 2-bit Smith prediction algorithm, but
 Misprediction cost equals to a minimum of a 10-cycle penalty.
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K7’s Instruction Decoding
deliver High Instruction Bandwidth
 x86 instructions are
decoded to MOPs
(3/cycle) and
dispatched to either
the integer pipe
(via direct or
vector path
decoders
depending their
complexity)
or to the
floating-point pipe
(directly passed to
the ICU)
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K7’s Out-of-Order Integer Pipe Issuing 6 ROPs/Cycle
 The Integer Scheduler is an out-of-order 15-entry
reservation station organized as 3 5-MOPs queues.
A MOP equals 1 or 2
ROP(s) (load, store,
load/store, ALU
operation, or branch).
 The integer pipe
provides 3 IEUs and 3
AGUs.
 Each of the 3 queues
of the scheduler is
physically associated
with a IEU/AGU pair.
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K7 provides large Memory Bandwidth
to support instruction execution
 The 44-entry LSU
queues memory requests
by the AGUs (3/cycle), and
 Issues them to the Dcache out-of-order (it can
provide up to 8 Gbytes/s of
bandwidth)
 Data is snooped from
the result buses.
 The cache is
nonblocking.
 The data cache is physically tagged. A 2-level translation lookaside buffer
(TLB), translates the effective addresses to physical (in parallel).
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K7’s additional features
 On-Chip tags support Large External L2.
 K7 connects to the
chip set via point-topoint interconnect
instead of a shared bus.
 This requires more
pins in MP
configurations but
allows the bus to run at
higher speed.
 K7’s bus comprises
three separate ports:
address in, address out,
and a 72-bit
bidirectional data port.
 It uses a five-state MOESI cache coherence protocol (‘owned’ state added)
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Summarizing about K7 microprocessor
 K7 is the most
complex of any current
x86 processor.
 It seems to
outperform Intel’s
models on an
instructions-per-clock
basis.
 It promises AMD
performance
leadership, allowing to
increase both prices
and profit margins.
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
Part III: AMD’s Athlon (1st member of of the 7th-generation AMD-processors’
family)
AMD Seventh Generation
Intel Previous Generation
Processor
Architecture/
Technology –
Competitive
Comparison
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AMD Athlon Processor Microarchitecture Features
I.
The industry's first nine-issue, superpipelined, superscalar x86 processor
microarchitecture designed for high clock frequencies
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Multiple x86 instruction decoders
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Three out-of-order, superscalar, fully pipelined floating point
execution units, which execute all x87 (floating point), MMX and
3DNow! Instructions
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Three out-of-order, superscalar, pipelined integer units
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Three out-of-order, superscalar, pipelined address calculation units
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72-entry instruction control unit
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Advanced dynamic branch prediction
II.
High-performance cache architecture featuring an integrated 128KB L1
cache and a programmable, high-speed backside L2 cache interface
III.
200MHz AMD Athlon processor system bus (scalable beyond 400 MHz)
enabling leading-edge system bandwidth for data movement-intensive
applications
IV.
Enhanced 3DNow! technology with new instructions to enable improved
integer math calculations for speech or video encoding and improved data
movement for Internet plug-ins and other streaming applications
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AMD Athlon Processor Architecture Block Diagram
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II.
High-Performance Cache Design
 Integrated, dual-ported 64KB split-L1 data and instruction caches with
separate snoop port, with eight banks to support concurrent access by two
64-bit loads or stores,
 Multi-level translation look-aside buffers (TLBs),
 A scalable L2 cache controller with a 72-bit interface, and
 An integrated tag for cost-effective 512KB L2 configurations
 First to incorporate a system-based MOESI (Modify, Owner, Exclusive,
Shared, Invalid) cache control protocol for x86 multiprocessing platforms,
thus deliver exceptional performance in both uni and multi processor systems
 It supports error correction code (ECC) protection
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III. The Industry's First 200-MHz System Bus for x86 Platforms
 ADVANTAGES OFFERED
AMD Seventh Generation
Advanced Computer Architectures
Intel Previous
Generation
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IV. Leading-Edge Floating Point and
3D Multimedia Technology
 The three execution units (Fmul, Fadd,
and Fstore) in the AMD Athlon processor's
floating point pipeline handle all x87
(floating
point)
instructions,
MMX
instructions,
and
enhanced
3DNow!
Instructions.
(Using a data format and single-instruction
multiple-data (SIMD) operations, it can deliver
as many as four 32-bit, single-precision floating
point results per clock cycle, resulting in a peak
performance of 4.0 Gigaflops at 1000 MHz).
 Use of the AMD's original 21 3DNow! instructions plus 24 new ones:
 12, that improve multimedia-enhanced integer math calculations,
 7, that accelerate data movement, and Internet functionality,
 5 DSP instructions, that enhance the performance of communications
applications (!!! unique in Athlon)
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Examples of applications that benefit
from Athlon’s processor capabilities
 Advanced imaging software for processing digital imaging
 Enhanced Internet browsing using next-generation browser features
 Architectural 3D rendering systems
 CAD/CAE software packages
 Near real-time MPEG-2 video encoding/editing for higher quality video
 Speech recognition in Web browsing and word processing
 Financial modelling and trading software
 Realistic 3D software, including 3D games and flight simulators.
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Summarizing about AMD’s Athlon processor
 It uses the latest microarchitecture innovation and system bus
technology to deliver the industry’s highest performance for x86compatible platforms.
 Compatible with x86 versions of Microsoft Windows, as well as other
operating systems.
 Provides a new level of performance and data movement capabilities for
the next generation computation-intensive software.
 Powers the Next Generation for the growing fields of
digital imaging,
the Internet,
enterprise computing,
CAD/CAE packages,
scientific/technical applications, and
3D gaming.
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CONCLUSION
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AMD’s microprocessors seem always to compete against
Intel’s performance and market dominance,
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Each model manages to accept the challenge of offering:
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High performance at the same clock rate,
Advanced techniques of register renaming,
out-of-order execution and of superscalar
design,
Support for high-end desktop products,
uniprocessor
and
multiprocessing
workstations and servers.
 AMD’s forthcoming optimized chipsets are planned to enable multiprocessing
system design based on 2 or more AMD family processors.
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