1. How Memory Works Physical Example 0 Water Tank 1 EmptyFull

2. How Memory Works Physical Example 0 Electronic Circuit 1 Electronic Circuit DischargedCharged

3. Practical Dynamic Memory Use capacitors to store the charge to represent “0” and “1” +++ _ _ _

4. Practical Static Memory Transistors play the main roles Base Collector Emitter

6. Memory Memory is the second important component in modern computers. 10011110 00011001 0000000000000000 0000000000000001 0000000000000002 0000000000000003 00011010 00011011 Content Address 1111111111111111

7. Memory Memory is the second important component in modern computers. 10011110 00011001 00011010 00011011 Content Address 0000h 0001h 0002h 0003h FFFFh

8. Memory Related Terms Bit------------------0 or 1 Byte----------------8 bits Word---------------16 bits-----2 bytes Doubleword------32 bits-----4 bytes Quadword---------64 bits-----8 bytes

9. Range of Unsigned Integers Unsigned byte------------0 to 255 Unsigned word-----------0 to 65535--64KB Unsigned doubleword--0 to 4,294,967,295 0 to -----4.3GB Unsigned quadword---- 0 to 18,446,744,073,709,551,615 0 to 18,446,744,073GB

10. Memory Related Terms RAM -----Random Access Memory ROM -----Read Only Memory PROM--Programmable Read Only Memory EPROM--Erasable PROM EEPROM--Electrical Erasable PROM Dynamic RAM---Need to be refreshed very often (every few milliseconds) Static RAM---Expensive cache memories

11. Memory Related Terms Memory Module. DATA Bus...... Address Bus Control Bus

12. Memory Related Terms Memory Module. DATA Bus Address Bus Control Bus

13. Memory Related Terms By Packaging Styles SIMM---Single Inline Memory Module DIMM---Dual Inline Memory Module SO-DIMM--Small Outline DIMM

14. Memory Organization For the same amount of capacity, there are many different layout patterns. Such as, for 1Kbits memory, we can have: a. 1,024 cells and 1,024 addresses, each stores a “0” or “1” b. 128 cells and 128 addresses, each cell has 8bits or I byte c. 1 cell and 1 address, the cell has 1024bits

15. Number of bits per cell for Some Commercial Computers Burroughs B1700 1 IBM PC 8 DEC PDP-8 12 IBM 1130 16 DEC PDP-15 18 CDC 3600 48 CDC Cyber 60

16. Cache Memory Why do we need cache memory? Main memory is always slower than CPU Main memory is far away from CPU Faster memory can be made but neither economic nor practical Small amount of expensive faster memory made close to the CPU will solve most of the problems

17. Cache Memory *** The most often used memory words are kept in the cache.*** CPU Main Memory Cache Bus

18. h-Hit Ratio of Cache Memory h = (k-1)/k where; k --- a word is written or read k times in a short interval and only need to reference the main memory 1 time. 1 - h is called miss ratio mean access time = c + (1 - h)m, where m is the time to reference the main memory

19. Byte Ordering The big endian and the little endian 0 4 8 12 0 4 8 12 0123 012 3 4567 4 567 8 9 10 11 12 13 14 15 8 9 1011 12131415 Address The big endian stores higher digits in the lower bytes & The little endian stores higher digits in higher bytes

20. Byte Ordering The big endian and the little endian 0 4 8 12 0 4 8 12 JIM T JIM SMIT S MI H H Address The big endian stores higher digits in the lower bytes & The little endian stores higher digits in higher bytes

21. Big Endian & Little Endian Address store number 1234567h 100 101 102 103 104 105 01 23 45 67 xx xx Big 67 45 23 01 xx xx Little

22. What wrong with the two systems? There is nothing wrong when each system works alone (they are both internally consistent). However, when transfer information over the network, we have problems. We will also have problems when using a software from one machine to another. There is no easy way to make both compatible without a time consuming conversion.