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1) Given a virtual memory system with:
virtual address 36 bits
physical address 32 bits
32KB pages (15 bit page offset)
Each page table entry has bits for valid, execute, read and dirty
(4 bits total) and bits for a physical page number.
a) How many bits in the page table? (do not answer in bytes)
Three digit accuracy is good enough. The exponent may be either
a power of 2 or a power of 10.
b) The virtual address is extended to 38 bits, all else stays the same.
How many bits in the page table? (do not answer in bytes)
Three digit accuracy is good enough. The exponent may be either
a power of 2 or a power of 10.
Note: There will be a page table for every process that is running,
yet the page tables are typically not completely allocated. Only
the sections of the page table being used are typically populated.
c) A fully associative TLB that has 32 blocks, 1 entry per block,
is needed for the page table like a) VA=35, PA=32, PO=15.
The TLB must hold a page table entry and a tag in each block.
How many bits in the TLB? (do not answer in bytes!)
d) Draw a two way associative TLB that has 4 blocks, 8 total PPN's,
for the page table a) Virtual address 35 bits, physical address
32 bits, offset 15 bits, 4 bits V,E,R,D.
See lecture 21 for 4 way associative cash, you only use 2.
The top will be the virtual address with the virtual page
number and virtual page offset.
The bottom will be the physical address with the physical
page number and physical page offset.
Show the detail of all fields, connections, mux, comparators.
Label the width of all fields and signals.
2) Compute file read time for a 1MB file for a typical hard drive and
a solid state drive, SSD.
a) Hard drive:
published average seek time 3.0ms
rotation speed 7,200rpm
overhead 2.0ms
transfer rate 80MB/s
b) SSD
overhead 1.5ms
transfer rate 80MB/s
c) speedup of SSD drive
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