10.2 Characteristics of Computer Memory RAM provides random access Most RAM is volatile.
-
date post
19-Dec-2015 -
Category
Documents
-
view
218 -
download
1
Transcript of 10.2 Characteristics of Computer Memory RAM provides random access Most RAM is volatile.
10.2 Characteristics of Computer Memory
• RAM provides random access
• Most RAM is volatile
10.3 Static and Dynamic RAM Technologies
• Static RAM– The miniature circuit contains many transistors
that operate continuously
• Dynamic RAM– Uses a circuit that acts like a capacitor– An external refresh circuit must periodically
read the data value and write it back again
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.4 Measures of Memory Technology
• Density– Tends to double approximately every 18
months.
• Latency and Cycle times– The time required to fetch information differs
from the time required to store information.
10.7 Latency and Memory Controllers
• Latency is an insufficient measure of performance
• A performance measure needs to measure the time required for successive operations
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
Two Separate measures
• The read cycle time (tRC)
• The write cycle time (tWC)
10.8 Synchronized Memory Technologies
• The clock pulses used with the memory system are aligned with the clock pulses used to run the processor.
• SDRAM– Synchronized Dynamic RAM
• SSRAM– Synchronized Static RAM
10.9 Multiple Data Rate Memory Technologies
• Double data rate
• Quadruple data rate
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.12 Memory Access and Memory Bus
• A memory controller provides the interface between a physical memory and a processor that uses the memory
• To achieve high performance, memory systems use parallelism
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.13 Memory Transfer Size
• The parallel connections define a memory transfer size
10.14 Physical Address and Words
• Each word of physical memory is assigned a unique number known as a physical memory address
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.16 Word Size and Other Data Types
• The word size is chosen as a compromise between performance and varies costs.
10.17 An Extreme Case:Byte Addressing
• Two important consequences– Byte addressing requires more addresses– The memory controller must support byte
transfer
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.19 Using Powers of Two
• Word address can be computed by extracting everything except the two low order bits.
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.20 Byte Alignment and Programming
• Aligning data on boundaries that corresponding to the physical word size can improve program performance.
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.22 Programming with Word Addressing
• On a processor that uses word addressing, software must handle the details of byte manipulation
• To optimize software performance, logical shifts and bit masking are used to manipulate an address
10.23 Measures of Memory Size
• Physical memory is organized into a set of M words that each contain N bytes.
• To make controller hardware efficient, M and N are each chosen to be powers of two
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.26 Indirection and Indirect Operands
• Because the operand specifies indirection, the processor treats the resulting value as an address in memory
10.27 Memory Banks and Interleaving
• Instead of a single memory and a single controller, the processor connect to multiple memory banks that each has its own controller.
• Interleaving spreads consecutive bytes of memory across separate physical memory modules
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.28 Content Addressable Memory
• A Content Addressable Memory includes hardware for high speed searching.
• A search key is the same size as a slot in the CAM
• Each slot contains hardware that performs the comparison
From Essentials of Computer Architecture by Douglas E. Comer. ISBN 0131491792. © 2005 Pearson Education, Inc. All rights reserved.
10.29 Ternary CAM
• A Ternary CAM only performs the match on bits that have the value zero or one.