MagneticMagnetic RandomRandom AccessAccess MemoryMemory (MRAM)(MRAM)
Jimmy Zhu ABB Professor in Engineering
Department of Electrical and Computer Engineering Carnegie Mellon University
24 August 2004
ComputerComputer SystemSystem
TLB CPU
SRAM L1 Cache
SRAM SRAM L2 Cache Volatile Memory
DRAMDRAM Main Memory
Archival Memory Non-Volatile Memory Disk Drive
J. Zhu, 18-200 Lecture, Fall 2004 2
1 Static RAM (SRAM)
Cache Memory Fast: 6-Transistor CMOS SRAM Access time: < 1 ns = 10-9 second Expensive:
$100 / MByte
Low Density:
>120 F2
F -- minimum fabrication feature size
J. Zhu, 18-200 Lecture, Fall 2004 3
Field Effect Transistor (FET)
Conducting metal plate
Gate Insulating oxide layer D
Source Drain G n+ p n+
Semiconductor S
Conducting ground symbol n-channel FET
MOSFET: Metal-Oxide-semiconductor-FET
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2 How a FET Works: Transistor On
http://www.pbs.org/transistor/science/info/transmodern.html Active condition: electron with charge –e VGS > VT i.e. G Gate VGG > VT VGG + + + + + + + + Drain i D + + D n n S p D G RD Source
S VDD n-channel FET
Drain current will I D be a function of gate voltage. VDD
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How a FET Works: Transistor Off
electron with charge –e Cutoff condition:
V < V Gate GS T G VT threshold voltage S Drain n+ n+ V = V p D DD Source D D
G RD
S VDD
No current Zero Drain current.
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3 AA ModernModern CMOSCMOS ProcessProcess
VDD
M2
V Vin out
M1
gate-oxide
TiSi2 AlCu
SiO2 Tungsten
poly
p-well n-well SiO2 n+ p-epi p+
Dual-Well Trench-Isolatedp+ CMOS Process
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DynamicDynamic RAMRAM
Main Computer Memory Q State “1” V = ¾ Individual access time 60 ns C + + + + + + + ¾ 10 F2 State “0” V = 0 − − − − − − − ¾ $4 /MByte ¾ All “1”s need to be refreshed every 1 ms.
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4 Rotational Latency
7,500 – 15,000 rpm
track
sector
Inexpensive: $0.001/1MByte
Rotational Latency • Average latency: 3 – 6 ms
• Wait until desired sector passes under head • Worst case: a complete rotation 7,500 rpm = 8 ms 15,000 rpm = 4 ms
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Hard Disk Drives
18-316 Introduction to Data Storage
18-517 Data Storage Systems Design
Magnetic Force Microscopy Image of A Disk Surface
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5 PricePrice vs.vs. SpeedSpeed
100 SRAM
10 DRAM
1
0.1
0.01
Price ($)Per MByte HDD 1E-3
1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 Access Time (second)
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ComputerComputer SystemSystem onon aa Chip?Chip?
Can one change the disk drive into a high speed memory chip?
If one can, one can put the entire computer system on a single chip:
TLB CPU
SRAM
SRAMSRAM
DRAMDRAM
Disk Drive
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6 Magnetic RAM: Historical Perspective
Motorola 4Mbits MRAM Chip Magnetic tunnel junction 2003
Honeywell 16Kbits MRAM Chip AMR Technology 1994
Control Data Corp. 1Kbits Ferrite Core Memory 1965
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RememberRemember MagnetMagnet !!
Magnetic moment can maintain its direction without power !
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7 Memory Element
Magnetic Tunnel Junction (MTJ)
Magnetic electrode State “0” State “1”
m1 Tunnel barrier m2
Magnetic electrode 2.5
CoFe/Al2O3 (7-20Å) /Co 2.0 ) Ω 1.5
1.0
Resistance (k 0.5
0.0 0 20 40 60 80 100 Data Bits
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MemoryMemory ArrayArray
“L” “L”“H” “L” “L”
“L”
“H”
“L”
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8 Detailed Structure
State “0” State “1”
Magnetic moments are fixed.
Only the magnetic moment of a storage layer is switched back and forth.
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WritingWriting BitsBits
State “0”I State “1” I
r r I M M r H
M State “1”
H
State “0”
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9 X-PointX-Point AddressingAddressing y x I
half-select elements
I
2 / 3 2 / 3 2 / 3 1.0 H k = H x + H y ) k 0.5
0.0
-0.5
Y-Component Field (H Field Y-Component -1.0
-1.0 -0.5 0.0 0.5 1.0
X-Compone Field (Hk)
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MRAM Cell
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10 44 MbitsMbits MRAMMRAM ChipChip
Freescale 4Mbits MRAM Chip
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MRAM:MRAM: DreamDream Memory?Memory?
Advantages of MRAM:
9 Nonvolatile (No power needed to maintain memory states)
9 SRAM Speed (~ 1 nanosecond )
9 DRAM Density (~ 20 F2 )
9 Endurance (Infinitely rewritable)
MRAM has the potential to be an universal memory to replace SRAM, DRAM, FLASH, and disk drives in some applications to become the
Universal Solid-State Memory!
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11 AA PotentialPotential GameGame ChangerChanger
If MRAM replaces SRAM, DRAM or even disk drives:
¾ Instant on systems: No booting from disk drive
¾ Minimum stand-by power (Turn it off!)
¾ Enable computer system to be integrated on a single chip!
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Applications
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12 SystemSystem onon ChipChip (SoC)(SoC)
Example:
SoC
RF Module Module unction ) F cessing ting (pro Compu Data Processing
Memory ory NV Mem Memory
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MRAM:MRAM: DreamDream Memory?Memory?
Present MRAM Technology Shortfalls:
Relatively high power dissipation (high current)
Down-size scaling not clear (thermal magnetic stability)
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13 X-PointX-Point AddressingAddressing y x I
half-select elements
I
2 / 3 2 / 3 2 / 3 1.0 H k = H x + H y ) k 0.5
0.0
99.999% of power is dissipated -0.5 2 as I R on the write lines! (H Field Y-Component -1.0
-1.0 -0.5 0.0 0.5 1.0
X-Compone Field (Hk)
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Magnetic Cladding (18-303 Electromagnetics)
Word Line with ¾ The main power consumption Cladding arises from the ohmic dissipation, I2R, in word/digital lines.
Digital Line with cladding Read Transistor
x 5
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14 Thermally Activated Reversal
Hx τrise= 0.3 ns 0.1 µm 0 H x = 0.8H x 2 ns t 0.2 µm
E
Angle
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The Potential Universal Memory
SRAM DRAM Disk Drive FLASH MRAM
Speed
Density
Cyclability
Cost
Non-volatility
Power consumption
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15 Conclusions
MRAM: The enabling technology for computer systems on a single chip!
Only Continued Innovation Will Ensure Future Competitiveness of MRAM
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Data Storage Systems Track
Fundamentals of E.E. 18-220
Eng. Electromagnetics Intro. to Data Storage Tech. 18-303 18-316 18-396
Signal & Sys. 18-517
Data Storage Sys. Design Physics of Appl. Magn. 18-715
Advanced Appl. Magn. 18-716
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16 18-517 Data Storage Systems Design
BuildingBuilding aa VirtualVirtual DiskDisk DriveDrive usingusing MATLAB/SIMULINKMATLAB/SIMULINK
Data to be recorded Retrieved signal
Equalizer
Recovered data
Detector
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18-315 Fall 2004 Introduction to Optical Communication Systems
Professor Jimmy Zhu [email protected]
Course Objective: Provide a basic understanding of present optical communication systems and components, as well as future engineering challenges.
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17 Bandwidth Explosion
Source: Agilent Technologies 1P 100T 10T Video on demand O.S. 1T 100G Voice-centric DWDM 10G Network World wide web WDM 1G Doubles every 4.7 years 100M 10M Fiber 1M Coax 100k Data-centric 10k Network 1k (Optical) Telephone 100 Doubles every 9 months 10 Telegraph 1 Data Rate Capacity (bits/second) Capacity Rate Data 1850 1900 1950 2000 2050
Year
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Facts
A single optical fiber is capable of transmiting 2x1012 bits of data per second, which is equivalent to
simultaneously carry more than 30,000,000 phone conversations, or
200,000 users download (upload) information at 10 Mbits/second data rate at same time, or
download all 380 CDs (each with 1 hour long music) in 1 second , or
download 30 DVD movies in 1 second .
Present dense wavelength division multiplexing (DWDM) technology is realizing the full potential of a single optical fiber !
A optical fiber cable may contain up to 200 fibers.
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18 Fiber-Optical Long-Haul Routes Source: KMI
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Metro Optical Network
Source: Nortel Networks e.g. 10 Gbits Ethernet
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19 18-315 Introduction to Optical Communication Systems
Laser Course Coverage Encoder Amp. Decoder driver
laser Light Fiber receiver 9 How light carries information 9 Generation of light 9 Light traveling in a fiber 9 Amplification of Light
Systems 9 Time Division Multiplexing (TDM) 9 Wavelength Division Multiplexing (WDM) 9 Optical networks
Devices and Components 9 Fiber 9 LED 9 Semiconductor lasers 9 Fiber Amplifiers 9 Optical receivers 9 Optical modulators 9 Optical couplers and switches J. Zhu, 18-200 Lecture, Fall 2004 39
This course is designed to:
prepare students with up-to-date education ready for the optical communication and network industry.
Provide students sufficient background knowledge for further career development in optical communication systems and networks.
Stimulate students’ ability for innovation.
Train students’ problem analyzing and problem solving abilities. J. Zhu, 18-200 Lecture, Fall 2004 40
20 Future Optical Internet…
“A road to a world with no borders, no boundaries, no flags, no countries, where the heart is the only passport you carry.” Carlos Santana
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