thermal-scheduling for ultra low power mobile microprocessor may, 20021 thermal-scheduling for ultra...
TRANSCRIPT
May, 2002 1
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
George Cai1 Chee How Lim 1 W. Robert Daasch2
Intel Corporation 1
Integrated Circuit Design and Test Laboratory PSU 2
May, 2002 2
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Presentation Outline
Mobile CPU Power Efficiency With Demanded Performance Thermal Scheduling For Mobile Microprocessor Power Constrained Performance Observations/Conclusions
May, 2002 3
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Ultra Low Power Mobile Microprocessor
• Primary pipeline: maximal performance, complex pipeline structure
• Second pipeline: Minimum power and energy consumption, very simple in order structure and target mobile anywhere-anytime applications.
• Transparent to OS and applications
• Maximal utilizing on die clock/power gating for energy saving
FE DE EX
RF
DE IOP
OOP
Primary
Secondary
Majority mobile apps with performance requirements
Text email, caller-id, reminder and other none high performance w/ anywhere-anytime requested apps
May, 2002 4
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Low Energy Consumption With Providing Suitable Performance Is Key For “Anywhere And Anytime”
• Must be compatible with exist OS and platform
• Must have active leakage power control
• Must meet the real time telecom application requirements
Stock/Urgent MessagesStock/Urgent Messages
Stock UpdateStock Update
AlertAlert
Interactive commandInteractive commandand replyand reply
All urgent messageAll urgent messageAnd important newsAnd important news
News headlineNews headlineEmail titlesEmail titles
Calendar reminder Calendar reminder Pages/voice messagePages/voice message
May, 2002 5
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Runtime Thermal Scheduling Capability
FE DE EX
RF
DE IOP
OOP
Primary
Secondary
• When thermal threshold is exceeded, the pipeline clusters will service instructions in alternating manner: cool the “hot” pipeline by clock/power-gating & the “cold” pipeline sustains processor operations
• Flexible selecting the threshold point, the energy-delay product, performance, and reliability of the processor can be enhanced
May, 2002 6
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Thermal Effects: Leakage Trend• Active leakage power reduction will be significant role for total power
reduction
• Thermal control is important for low energy consumption for mobile CPU
Leakage Power Trend
0
0.1
0.2
0.3
0.4
0.5
0.6
30 50 70 90 110
Temperature (degree C)
Le
ak
ag
e/T
ota
l Po
we
r
0.25um
0.18um
0.13um
0.10um
~25% power reduction
Leakage Power Trend
0
0.1
0.2
0.3
0.4
0.5
0.6
30 50 70 90 110
Temperature (degree C)
Le
ak
ag
e/T
ota
l Po
we
r
0.25um
0.18um
0.13um
0.10um
~25% power reduction
Derived from F. Pollack’s Micro-32 Keynote Presentation, 1999
May, 2002 7
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Example of Scheduling Algorithm
S1: Normal Operation (Primary Pipeline)S2: Stall Fetch & Clear PipelineS3: Alternate Operation (Secondary Pipeline)S4: Disable Clock or Scale F-V
S1
S2
S3
T1 < TH
S4
T1 TH
T1 TH
T1 TL
T1 TL
T1 > TL
& T2 < TH
T1 > TL
& T2 TH
T1 > TL
|| T2 > TL
T1 TL
& T2 TL
TS2
TS1
Temperature (C)Ta
Tmax
tcycle
TH
tcool theat
Time (s)
TL
May, 2002 8
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Enhance Effectiveness Of Other Power Control Techniques
IL1
DE
CO
DE
FET
CH
RENAME
ROB LSB
ARCH FILE
BY
PASS
EXE
DL1
TS TS
DCT LOGIC
PLL Global Clock
Dynamic Clock Disabling/Throttling
IL1
DE
CO
DE
FE
TC
H
RENAME
ROB LSB
ARCH FILE
BY
PASS
EXE
DL1
TS TS
DFS LOGIC
PLL Global Clock
VRM Vdd
On-Chip
Off-Chip
Dynamic Frequency Scaling
May, 2002 9
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Power Constrained Clock Frequency With Performance Impact
0 15
30
45
60
75
90
0.500.
600.700.
800.901.00
0.00
0.20
0.40
0.60
0.80
1.00
1.20
Normalized Fref
Temperature (C)
Fraction Vdd
Relative Operating Frequency • Using gate delay as proxy for performance
• Thermal-dependence: mobility & threshold
• Frequency impact (B subscript denotes baseline)
VtV
V
I
VCt
ddD
dd
ds
ddd
2
300
300
TD 3005.2300 TVtVt K
mV
dd
Bdd
BBdd
dd
BD
D
Bref V
V
VtV
VtV
F
FF ,
,,
May, 2002 10
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Thermal Effects on Power
• Divide total power into two components: dynamic and leakage power
TnVVt
sdddd eIVFVCP
2
0 15
30
45
60
75
90
0.500.
600.700.
800.901.00
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
Normalized Pref
Temperature (C)
Fraction Vdd
Relative Power Consumption
May, 2002 11
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Thermal Effects on Energy
• Using power per frequency (W/MHz) metric as proxy for energy
Frequency
PowerEnergy
0 15
30
45
60
75
90
0.500.600.700.800.901.00
0.00
0.50
1.00
1.50
2.00
2.50
Normalized Eref
Temperature (C)
Fraction Vdd
Relative Energy Consumption
May, 2002 12
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Architecture-LevelPower-Performance Tradeoff
• For wide-superscalar processors, performance impact of pipeline scaling is smaller than global clock throttling or frequency scaling
Relative IPC vs Pipeline Width
0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
1.30
1.40
'2 '4 '8 '16
Pipeline Width
Rel
ativ
e IP
C
~15%
Relative Frequency vs Supply Voltage
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00
Fraction of Supply Voltage
Rel
ativ
e F
req
uen
cy
~30%
May, 2002 13
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Comparative Outcomes: Energy Metric
• Simulation Conditions (500 million instructions; TL = 55C)
– Stop Clock Control: Toggle between Fmax and 0 MHz
– Voltage/Freq Scaling : Toggle between Fmax and 0.9/0.8/0.6 Fmax
– Thermal Scheduling : Toggle between Primary and 2nd Pipelines
Clk gatingV-F scaling
Thermal scheduling
M88KSIM
LI
GCCPERL
0.000
2.000
4.000
6.000
8.000
10.000
12.000
14.000
En
erg
y (J
)
Thermal Control Techniques
Benchmarks
Energy Consumption of Conservative Control
M88KSIM
LI
GCC
PERL
Clk GatingF-V Scaling
Thermal Scheduling
M88KSIM
LI
GCC
PERL
0.0002.0004.0006.0008.000
10.00012.00014.000
16.000
En
erg
y (
J)
Thermal Control Techniques
Benchmarks
Energy Consumption of Aggressive Control
M88KSIM
LI
GCC
PERL
Conservative: TH = 70C Aggressive: TH = 60C
May, 2002 14
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Comparative Outcomes: Energy-CPU Time Metric
Total Energy x CPU Time
Overall Energy-CPU Time Metric Comparison
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
DCD DFS TAM
Thermal Control Techniques
En
erg
y-T
ime
(J
.s)
Overall_Cv (J.s)
Overall_Ag (J.s)
May, 2002 15
Thermal-Scheduling For Ultra Low Power Mobile Microprocessor
Pros and Cons
• Advantages Limits power/energy upper bound & prevents thermal runaway Pipeline tuned for either performance or ultra low power Existing OS and application compatible Performance penalty for engaging/disengaging control is small
(architecture event) Supports low-power anywhere-anytime of mobile computing
Non-timing critical tasksReal-time application that requires more predictable output
• Concernsi/t during pipeline switchReal-Register File may require extra dedicated portsBypass bus may have additional loading