Cache memory:A small fast memory that acts as a buffer for a slower and larger memory.
SRAM:static random access memory faster and less dense than dynamic memory.
Volatile Memory:storage like DRAM that retains data only if it is receiving power.
Non Volatile:retains data even in the abscence of the power.Like Magnetic disk.
Flash memory:non volatile semiconductor memory ,cheaper and slower than DRAM but faster and expensive than magnetic disks.It is a type of EEPROM-electronically erasable programmable read only memory.
LAN:local area network is a network to carry data within a confined area.
WAN:wide area network extends over a wide area.
VLSI:device containing hundreds of millions of transistors.
Response time:Also called Execution time is the total time required for the computer to complete a task, including disk access, memory access, I/O activities, OS over head, CPU execution time and so on.
Throughput:also called bandwidth also a measure of performance, is the number of tasks completed per unit time.
replacing a processor with a faster version will increase throughput and decreases the response time.
where as adding additional processors increase only throughput increases because the time taken for executing the program does not change.
Performance=1/execution time(CPU)
CPU execution time is the time the CPU spends for computing a specific task.
CPU execution time=CPU clock cycles for a program*clock cycle time
CPU execution time=CPU clock cycles for a program/clock rate.
CPI:average clock cycles per instruction
CPU clock cycles=no. of instuctions*CPI
Instruction count:The no. of instructions executed by the program.
CPU time=instruction count*CPI*clock cycle time
CPU time=instruction count*CPI/clock rate
Power=capacitive load * voltage2 * frequency switched
Cost per die=cost per wafer/(Dies per wafer * yield)
dies per wafer=wafer area/die area
yield=1/(1+(defects per area*die area/2))2
Bench mark is a program selected for use in comparing computer performance.
fallacies - misbelief conceptions
pitfalls-easily made mistakes
MIPS (million instructions per second)= instruction count/(Execution time * 106 )
MIPS=Clock rate/(CPI * 106)
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Programs exhibit both temporal locality and spatial locality
Temporal Locality:- The tendency to reuse recently accessed data items.
Spatial Locality:- The tendency to reference data items that are close to other recently accessed items.
Memory hierarchies take advantage of temporal locality by keeping more recently accessed data items close to the processor.
They also take advantage of spatial locality by moving blocks consisting of multiple contiguous words in memory to upper levels of hierarchy.
memory hierarchy uses smaller and faster memory technologies close to the processor. Thus accesses that hit in the highest level of hierarchy can be processed quickly. Accesses that miss go to lower levels of the hierarchy which are larger but slower.
If the hit rate is high enough, the memory hierarchy has an effective access time close to that of the highest and fastest level and a size equal to that of the lowest and largest level.
Hit Time:-The time required to access a level of the memory hierarchy, including the time needed to determine whether the access is a hit or a miss.
Miss Penalty:-The time required to fetch a block into a level of the memory hierarchy from the lower level, including the time to access the block, transmit it from one level to another, insert it in the level that experienced the miss, and then pass the block to the requestor.
CACHE: name given to the level of memory hierarchy between the processor and main memory
SRAM:static random access memory faster and less dense than dynamic memory.
Volatile Memory:storage like DRAM that retains data only if it is receiving power.
Non Volatile:retains data even in the abscence of the power.Like Magnetic disk.
Flash memory:non volatile semiconductor memory ,cheaper and slower than DRAM but faster and expensive than magnetic disks.It is a type of EEPROM-electronically erasable programmable read only memory.
LAN:local area network is a network to carry data within a confined area.
WAN:wide area network extends over a wide area.
VLSI:device containing hundreds of millions of transistors.
Response time:Also called Execution time is the total time required for the computer to complete a task, including disk access, memory access, I/O activities, OS over head, CPU execution time and so on.
Throughput:also called bandwidth also a measure of performance, is the number of tasks completed per unit time.
replacing a processor with a faster version will increase throughput and decreases the response time.
where as adding additional processors increase only throughput increases because the time taken for executing the program does not change.
Performance=1/execution time(CPU)
CPU execution time is the time the CPU spends for computing a specific task.
CPU execution time=CPU clock cycles for a program*clock cycle time
CPU execution time=CPU clock cycles for a program/clock rate.
CPI:average clock cycles per instruction
CPU clock cycles=no. of instuctions*CPI
Instruction count:The no. of instructions executed by the program.
CPU time=instruction count*CPI*clock cycle time
CPU time=instruction count*CPI/clock rate
Power=capacitive load * voltage2 * frequency switched
Cost per die=cost per wafer/(Dies per wafer * yield)
dies per wafer=wafer area/die area
yield=1/(1+(defects per area*die area/2))2
Bench mark is a program selected for use in comparing computer performance.
fallacies - misbelief conceptions
pitfalls-easily made mistakes
MIPS (million instructions per second)= instruction count/(Execution time * 106 )
MIPS=Clock rate/(CPI * 106)
------------------------------------------------------------------------------------------------------------
Programs exhibit both temporal locality and spatial locality
Temporal Locality:- The tendency to reuse recently accessed data items.
Spatial Locality:- The tendency to reference data items that are close to other recently accessed items.
Memory hierarchies take advantage of temporal locality by keeping more recently accessed data items close to the processor.
They also take advantage of spatial locality by moving blocks consisting of multiple contiguous words in memory to upper levels of hierarchy.
memory hierarchy uses smaller and faster memory technologies close to the processor. Thus accesses that hit in the highest level of hierarchy can be processed quickly. Accesses that miss go to lower levels of the hierarchy which are larger but slower.
If the hit rate is high enough, the memory hierarchy has an effective access time close to that of the highest and fastest level and a size equal to that of the lowest and largest level.
Hit Time:-The time required to access a level of the memory hierarchy, including the time needed to determine whether the access is a hit or a miss.
Miss Penalty:-The time required to fetch a block into a level of the memory hierarchy from the lower level, including the time to access the block, transmit it from one level to another, insert it in the level that experienced the miss, and then pass the block to the requestor.
CACHE: name given to the level of memory hierarchy between the processor and main memory
