A Case for Custom Silicon in Enabling Low-Cost Information Technology for Developing Regions Z. Foo, David Devecsery, T. Schmid, N. Clark, R. Frank, M. Ghaed, Y. Kuo, Lee, Y. Park, Z. Renner, N. Slottow, V. Vinay, M. Wieckowski, D. Yoon, C. Schmidt, D. Blaauw, P. Chen, and P. Dutta The University of Michigan

2 Motivation Recent studies show benefits of information in developing regions Avaaj Otalo –Mobile-phone-based interactive voice forum –Users found value listening to questions and answers Digital Green Project –Disseminate agricultural information through video –Large increase in adoption of agricultural practices

The University of Michigan3 Motivation Talking Book Project –Provide on-demand access to information from local experts –Information pre-loaded onto devices, and re-programmed in field –Farmers showed a significant increase in crop production Question: Why aren’t these devices more popular in developing regions?

The University of Michigan4 Commodity Devices Not Sufficient Radio – No replay capability – No indexing – No on-demand information Voice Recorder – No indexing – Information distribution difficult Cell Phone – Too expensive - $20-$40 – Running cost too high - $.10-$.30/min. in rural Africa – High power draw – Connection unreliable

The University of Michigan5 Custom Devices Still Not Sufficient Lifeplayer – Provides data recording, playback, indexing, communication – Costs around $100 – Very large Talking Book – Similar functionality to Lifeplayer – Scaled way down Hand-held Costs between $20 and $ day lifetime on AA batteries Source: lifelineenergy.org

The University of Michigan6 Our Goal Design a custom device: – Provide recording, playback, communication, data indexing – < $10 – Reduce upkeep cost to user Case Study: Redesign Talking Book

The University of Michigan7 Improving The Talking Book Reduce costs with –Custom silicon integration –Flatter memory hierarchy –Unconventional communication Will reduce cost to $10 and power by 6x

The University of Michigan8 Use Custom Silicon Aggressively integrate into custom silicon Eliminate discrete components

The University of Michigan9 Integrate to Chip Speaker amp Voltage regulators Oscillators – One off chip crystal – Inexpensive, and slow

The University of Michigan10 Memory Hierarchy Old Memory Hierarchy Goals of new system: – Minimize Costs – Allow for large code bases – Easy for programmers Core External NOR Flash Internal Flash External SD Card Internal RAM

The University of Michigan11 Minimizing Memories Use only one NAND Flash –Lower power –Less expensive NAND Flash –Chips wear out –Not fault tolerant –Slower –Requires software FTL –Uses cache –Improve performance –Reduces flash wear Software FTL NAND Flash Cache Microcontroller Core

The University of Michigan12 Custom Cache 4-way set associative 128 KB memory Cache must use core – Interrupts fetch data – Similar to MMU Pinned region – Stops critical code from missing – Allows real-time guarantees Software FTL NAND Flash Cache Microcontroller Core

The University of Michigan13 Move Interfaces On-Chip Push button interface – Expensive - $1 – Requires membrane switch-pad – Mechanical failure Replace with Capacitive Sensors: – Low chip area – Nearly no cost – Built into PCB – No physical system

The University of Michigan14 Communications

The University of Michigan15 Communications FM Radio Long range voice distribution Digital data through RDS sub-band Download information over night

The University of Michigan16 Communications FM Radio Inductive Link Replaces USB Wireless peer to peer 500Kb/s Integrated into PCB Minimal hardware cost

The University of Michigan17 Communications FM Radio Inductive Link Cell Phone On-demand information download Directly download voice Digital data with FSK modulation – Firmware Updates

The University of Michigan18 Bill of Materials - Components

The University of Michigan19 Bill of Materials - Board

The University of Michigan20 Bill of Materials - System

The University of Michigan21 NRE Costs Custom silicon equal COTS 70k units Custom silicon < $10 at 400k units

The University of Michigan22 Power Costs 2 Week battery lifetime on 2 AA Batteries Overall 6x power reduction

The University of Michigan23 Summary Current devices are not sufficient Custom silicon: – Gives similar functionality to old Talking Book – Allows entire system on three chips – Reduces all costs to within goals Custom silicon presents a viable option for large- quantity developing world products

The University of Michigan24 Low-Power Core Use ARM Cortex-M0 processor – 50MHz core clock – ARM v6m ISA 32-bit performance 16-bit instruction size – <10% of total chip energy in active mode – Decodes, timescales, & plays audio real time

The University of Michigan25 Cell Phone Issues Use More Power Stuff about why not good