Cau 6 cache - CS4617 Computer Architecture Lecture 3 Memory...

CS4617 Computer Architecture
Lecture 3: Memory Hierarchy 1
Dr J Vaughan
September 15, 2014
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Important terms
Cache fully associative write allocate
Virtual memory dirty bit unified cache
Memory stall cycles block offset misses per instruction
Direct mapped write-back block
Valid hit data cache locality
Block address hit time address trace
Table: Memory terms
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Important terms (ctd)
Write-through Cache miss Set
Instruction cache Page fault Random replacement
Average memory
access time
Miss rate Index field
Cache hit n-way set associative No-write allocate
Page Least recently used Write buffer
Miss penalty Tag field Write stall
Table: Memory terms
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Term definitions 1
Cache The first level of memory met when the address
leaves the processor. The word cache is often used to
mean buffering commonly-used items for re-use
Cache hit Success: finding a referenced item in cache
Cache miss Failure: the required item is not in the cache
Block The fixed number of bytes of main memory that is
copied to the cache in one transfer operation. This
transfer happens when a cache miss occurs
Temporal locality A referenced item is likely to be referenced again
in the near future
Spatial locality Other data in the same block as a referenced item
are likely to be needed soon
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Term definitions 2
Virtual memory The extension of memory to an address space that
encompasses the physical residence on disk of some
programs and data
Page A fixed-size block of virtual memory address space,
usually in the range 1K to 4K.
A page is either in main memory or on disk
Page fault An interrupt generated when the processor references
a page that is neither in cache nor in main memory
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Term definitions 3
Memory stall cycles Number of cycles during which processor is
stalled waiting for a memory access
Miss penalty Cost per cache miss
Address trace A record of instruction and data references with a
count of the number of accesses and miss totals
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