superrange: wide operational range power delivery design for both stv and ntv computing
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SuperRange: Wide Operational Range Power Delivery Design for both STV and NTV Computing. Xin He, Guihai Yan, Yinhe Han, Xiaowei Li Institute of Computing Technology, Chinese Academy of Sciences. The need of wide operation range. - PowerPoint PPT PresentationTRANSCRIPT
SuperRange: Wide Operational Range Power Delivery Design for both STV and NTV
Computing
Xin He, Guihai Yan, Yinhe Han, Xiaowei Li
Institute of Computing Technology, Chinese Academy of Sciences
• Microprocessor’s supply voltage range has been gradually increasing in these year– Intel Pentium Processor has a supply voltage range
from 0.9V to 1.5V to support DVFS– Intel Sandy Bridge Processor requires a higher than
nominal voltage to boost performance
The need of wide operation range
20.9VIntel Pentium Processor
1.5VTurbo Boost in Intel Sandy Bridge
(66.7%)
DVFS
Turbo
– Near Threshold Computing: set supply voltage to a value near to transistor’s threshold voltage (0.4V-0.6V)
The need of wide operation range
3
Intel ISSCC20120.28V-1.2V
Future Microprocessor has wide supply voltage range. Brings challenges to power delivery design
DVFS
Turbo
NTC
• Voltage regulator is key to deliver power at a specified voltage level– Linear regulator-LDO– Switching regulator
• Buck regulator(Off-VR)• Switch capacitor regulator(On-VR)
Background of Power Delivery Design
Buck Regulator Switch Capacitor Regulator
• VRs are delivering power to wide operational range cores
Power Conversion Efficiency Characteristics
High PCE High PCE
Low PCE Low PCE
• Off-VR:– High switching loss
• On-VR:– Narrow optimal region
• LDO-VR:– Limited efficiency
Conventional design can’t meet the need of wide voltage range
• Explore the design space of wide operational range power delivery design
• Propose SuperRange, a wide operation range power delivery scheme
• Present a VR aware power management algorithm to maximize performance under given power budget
Contribution
• Explore three optional design 1. Off-VRs
• Two Off-VR evenly located2. Off-VR + LDO-VR
• An Off-VR serves as an frontend3. Off-VR + On-VR
• Off-VR delivers to STV and On-VR to NTV
Design space exploration
• Loss in Off-VRs
Option 1: Off-VRs scheme
20% Cross 10%
dominants!
𝑃𝑐𝑎𝑝=𝐶𝑜𝑉❑2 𝑓
𝑃𝑐𝑎𝑝 𝑖𝑚𝑝𝑙𝑦𝑠𝑓
• In LDO-VR
– PCE is limited by the ratio of output voltage to input voltage
• PCE is lower than 30% when delivering to NTV region
Option 2: LDO-VR scheme
• Using Off-VR to deliver to STV region• Two step voltage conversion
• How to decide intermediate voltage
Option 3: Off-VR + On-VR scheme
1) Fixed intermediate voltage – Off-VR delivers fixed output voltage 2V– Tuning On-VR params to achieve further
conversion• PCE of Off-VRs is high• On-VR couldn’t deliver to all NTV levels at high
PCE
𝑉 𝑥=𝐷∗𝑉 𝑖𝑛
2) Using varied intermediate voltage – Off-VR delivers to varied voltage levels
• Duty cycle tuning– On-VR further step these intermediate values
to 0.4V-0.6V
– Pros:• On-VR has high PCE(around 80%)
– Cons:• The PCE of Off-VR remains low because of
small load current
Off-VR + On-VR scheme
• Multi-phase Off-VR provides an opportunity to improve load current, thus PCE get improved– Modern Off-VR can dynamically change number of working
phases
• Decreasing the number of working phases would increase output ripple– 1.5uH inductor is big enough to reduce the ripple with acceptable area overhead
Proposed SuperRange Design
• Supporting STV– Voltage conversion to STV is performed by Off-VR
• Supporting NTV– Two step conversion.
• Off-VR sets to single working phase• On-VR achieves further conversion(e.g. 3:1)
SuperRange Overview
• Maximize performance under given power budget– Find optimal core counts and VF
setting
VR aware power management algorithm
• PCE with varying load current– Although low voltage improve app power efficiency, it degrades
the PCE
More cores, Low voltage Few cores, High voltage
• Determine voltage setting candidates– Computes the total powers when all cores are active at
each voltage level– Selects the lowest voltage () and the highest voltage ()
• Determine active core count– Calculate max active core count at voltage and get
corresponding performance– Compare the performance with and make decisions
Algorithm
• Target processor characteristics – Multicore processor consists 16 ALPHA cores which has 9
power state• (1.2v, 1.9GHz), (1.1v, 1.7GHz), (1.0v, 1.5GHz)… (0.4v, 0.3GHz)
– 32MB LLC, distribute directory-based MESI– On chip interconnection: mesh + router
• Voltage regulator model– Single topology (3 to 1) Switch capacitor voltage regulator – Buck voltage regulator like TI TPS 54912
Experimental Setup
Power Conversion Efficiency
SuperRange combines the advantages of Off-VR and On-VR andexhibits high PCE over the entire voltage range
• Performance comparison in power-constrait system
Comparison
SuperRange outperforms LDO scheme by 50% and Off-VR scheme by 30%
• Maximum achievable performance comparison under shrinking power budget
Comparison
On average, SuperRange achieve 52% and 170% higher PCEthan Off-VR and LDO-VR scheme.
• Power delivery design for wide operational range is an important issue
• Explore the optional power delivery design scheme
• The proposed SuperRange scheme achieves high PCE over the entire operational range
• Propose a VR aware power management algorithm
Conclusion
• Thank You for Your Attention
• Question?