Lecture 6: The Walls to Sequential Computing. Moore’s Law.
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Last updated
Last updated
Wrap up Caches
Virtual Memory
Handling a write-hit
Write-through
Write-back
Handling a write-miss
Write-allocate
No-write-allocate
Typical combos in practice
Write-back + Write-allocate (more common)
Write-through + No-write-allocate
Miss rate is more important than the hit rate: 97% hit rate is ~2 times worse than 99% hit rate
Why memory virtualization?
Ease of use (running programs that require more memory than physically available)
Isolation (running multiple programs simultaneously)
Protection
A page of virtual memory corresponds to a frame of physical memory
Page table enables the translation of virtual address into physical addresses
The page table is stored in main memory
If the page table is accessed for each address translation, this would be very costly
Translation Lookaside Buffer (TLB): "Cache" for the addr translation process
