2. ICC Module 3 Lesson 2 – Memory Hierarchies 1 / 9 © 2015 Ph. Janson Information, Computing & Communication Memory Hierarchies – Clip 1 – Technologies School of Computer Science & Communications B. Falsafi (charts), Ph. Janson (commentary)

3. ICC Module 3 Lesson 2 – Memory Hierarchies 2 / 9 © 2015 Ph. Janson Outline ►Clip 1 – TechnologiesClip 1 ►Clip 2 – ConceptClip 2 ►Clip 3 – PrincipleClip 3 ►Clip 4 – ImplementationClip 4 ►Clip 5 – Reading memoryClip 5 ►Clip 6 – Writing memoryClip 6 ►Clip 7 – Cache management – the Least Recently Used algorithmClip 7 ►Clip 8 – A simulated exampleClip 8 ►Clip 9 – LocalityClip 9 First clipFirst clipPrevious clipNext clipNext clip

4. ICC Module 3 Lesson 2 – Memory Hierarchies 3 / 9 © 2015 Ph. Janson Entertainment Life Business 5,000, 000, 000, 000, 000, 000,000 bytes in 2013 (10 21 = 1 zetabyte) 5,000, 000, 000, 000, 000, 000,000 bytes in 2013 (10 21 = 1 zetabyte) We live in a digital universe

5. ICC Module 3 Lesson 2 – Memory Hierarchies 4 / 9 © 2015 Ph. Janson How can all that be stored in computer memory Arithm. unit Register bank Data memory Instruction memory Instruction pointer + 1 Decoder

6. ICC Module 3 Lesson 2 – Memory Hierarchies 5 / 9 © 2015 Ph. Janson 1. Technologies Magnetic tape robot USB FLASH FLASH Tablet Primary memory (RAM) Hard Disk Array 2m 1.2m 0.5m 0.1m Processor registers Cache memory On-Chip Off-Chip Hard diskSSD

7. ICC Module 3 Lesson 2 – Memory Hierarchies 6 / 9 © 2015 Ph. Janson Salient technology characteristics ►Capacity  Size= number of bytes  Cost= unit cost (in GB for instance) ►Performance  Latency= time required to access a given byte  Throughput= number of consecutive bytes transferred by second ►Retention  Retention = characteristic of media that retain information when powered off  Volatility= characteristic of media that ‘forget’ information when powered off

8. ICC Module 3 Lesson 2 – Memory Hierarchies 7 / 9 © 2015 Ph. Janson Capacity SupportTextImageAudioVideo 10KB2 pages 100KB1 photo 1MBDiskette1 book1 photo HD1 min. MP3 10MB1 min. hi-fi 100MB 1GB1h hi-fi1h video 10GB2500 MP31h video HD 100GBA library 1TB“1000 films 10TBHard diskUS Library of Congress in a pocket” CDs DVDs RAM Flash Magnetic tape

9. ICC Module 3 Lesson 2 – Memory Hierarchies 8 / 9 © 2015 Ph. Janson Capacity and latency 10 ms 10µs 10 ns 0.1 ns (10 GHz) 1 TB

10. ICC Module 3 Lesson 2 – Memory Hierarchies 9 / 9 © 2015 Ph. Janson Technology characteristics in perspective LatencyThroughputCost ($/GB)CapacityRetention ProcessorsnsGHzn.a. RAM1 - 100 nsGB/s10MB - GBNO FlashµsGB/s0.5GB - TBYes Disksms100s MB/s0.05> TBYes Magnetic tapes Even slower100s MB/s Even cheaper Even largerYes