Week 10 Flashcards
True / False:
You can increase a cache speed by adding another cache
True
how does cache performance relate to random sequences?
The more random a sequence, the worse a cache behaves.
The less random a sequence, the better a cache behaves
Three rules of memory hierarchy
1) lowest level is the ultimate repository for all information long-term
2) a level above is provided a copy of information from the level below when the level above cannot satisfy a processor memory access
3) when processor stores (writes) information into the top level, that change must eventually propagate down the levels to maintain rule 1
what is a block?
contains sequential word addresses, it’s size is a power of 2 multiple of general purpose register size
Compulsory Miss
name for the miss that must occur on the first access to a memory block
Capacity Miss
occurs when the cache cannot simultaneously hold all blocks accessed by a program (90/10 rule)
Conflict Miss:
occurs when a set has fewer block storage locations that the number of blocks mapping to that set for a given program temporo-spatial locality
how does a fully associative cache have no conflict misses?
it is eliminated if you can place any block in any block storage location: Set # field is eliminated, search cache for a block using only the tag field.
When do you use fully associative cache?
When conflict misses dominate (out of the 3 Cs) and when miss penalty is enormous
what is the dirty bit?
a bit that marks changed blocks for later write-back
you should move through multi-dimensional arrays in _____ order
storage
what are the virtual memory motivations:
Provide a convenient memory address environment
allow efficient and safe [correct] sharing of memory among multiple programs
use main memory as a cache for hard disk content
speed some operating system tasks
a separate range of addresses accessible only to this program:
Address space
Virtual memory system implements the _____ of a program’s address space to physical addresses used in main memory in the computer
translation (which enforces protection of a program’s address space from other programs)
virtual memory block is called a _____
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