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Lecture 2

# G ddr ddr2 ddr3 improving performance 2 move less data

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Unformatted text preview: he which the instrucGon operates must be fetched from memory and brought to the CPU   CPU < ­> Memory bandwidth can limit performance   Improving performance 1: hardware improvements to increase memory bandwidth (e.g., DDR → DDR2 → DDR3)   Improving performance 2: move less data into/out of the CPU   Put some “memory” in the CPU chip itself (this is “cache” memory) Memory 8 University of Washington Binary RepresentaJons   Base 2 number representaJon   Represent 35110 as 00000001010111112 or 1010111112   Electronic implementaJon   Easy to store with bi ­stable elements   Reliably transmiWed on noisy and inaccurate wires 0 1 0 3.3V 2.8V 0.5V 0.0V Memory 9 University of Washington Memory, Data, and Addressing           Preliminaries RepresenJng informaJon as bits and bytes Organizing and addressing data in memory ManipulaJng data in memory using C Boolean algebra and bit ­level manipulaJons Memory 10 University of Washington Encoding Byte Values   Binary 000000002  ­ ­ 111111112   Byte = 8 bits (binary digits)   Example: 001010112 = 32+8+2+1 = 4310   Example: 2610 = 16+8+2 = 001010102     Decimal 010  ­ ­ 25510 Hexadecimal 0016  ­ ­ FF16           Groups of 4 binary digits Byte = 2 hexadecimal (hex) or base 16 digits Base ­16 number representaGon Use characters ‘0’ to ‘9’ and ‘A’ to ‘F’ Write FA1D37B16 in C   as 0xFA1D37B or 0xfa1d37b Memory 0 1 2 3 4 5 6 7 8 9 A B C D E F 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 11 University of Washington What is memory, really?   How do we ﬁnd data in memory? Memory 12 University of Washington Byte ­Oriented Memory OrganizaJon ••• !   Programs refer to addresses   Conceptually, a very large array of bytes, each with an address (index)   System provides an address space private to each “process”         Process = program being executed + its data + its “state” Pro...
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