Unit 6 Flashcards
The locality principle stating that if a data location is referenced then it will tend to be referenced again soon.
Temporal locality
The locality principle stating that if a data location is referenced, data locations with nearby addresses will tend to be referenced soon.
Spatial locality
The high likelihood of accessing multiple elements within array A is an example of _____ locality.
spatial
The high likelihood of accessing i = i + 1 repeatedly is an example of _____ locality.
temporal
A structure that uses multiple levels of memories; as the distance from the processor increases, the size of the memories and the access time both increase.
Memory hierarchy
The minimum unit of information that can be either present or not present in a cache.
Block (or line)
The fraction of memory accesses found in a level of the memory hierarchy.
Hit rate
The fraction of memory accesses not found in a level of the memory hierarchy.
Miss rate
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.
Hit time
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 the other, insert it in the level that experienced the miss, and then pass the block to the requestor.
Miss penalty
Blank exhibit both temporal locality, the tendency to reuse recently accessed data items, and spatial locality, the tendency to reference data items that are close to other recently accessed items.
Programs
Memory hierarchies take advantage of temporal locality by keeping more recently accessed data items closer to the blank.
processor
Memory hierarchies take advantage of spatial locality by moving blocks consisting of multiple contiguous words in memory to blank of the hierarchy.
upper levels
A memory hierarchy uses smaller and faster memory technologies blank to the processor.
close
In most systems, the memory is a true blank, meaning that data cannot be present in level i unless they are also present in level i + 1.
hierarchy
Blank are simply integrated circuits that are memory arrays with (usually) a single access port that can provide either a read or a write. Blank have a fixed access time to any datum, though the read and write access times may differ.
SRAMs
SRAMs don’t need to blank and so the access time is very close to the cycle time.
refresh
Cache type of memory
SRAMS
In a blank, the value kept in a cell is stored as a charge in a capacitor.
dynamic RAM (DRAM)
Because DRAMs use only blank per bit of storage, they are much denser and cheaper per bit than SRAM.
one transistor
As DRAMs store the charge on a capacitor, it cannot be kept indefinitely and must periodically be blank
refreshed.
Main memory type
DRAM
To improve performance, DRAMs buffer blank for repeated access.
rows
Modern DRAMS are organized in banks. Each bank consists of a series of ___
rows