HW6 Solutions

1.1:
Answers can vary. Here are some items to consider:
A high-performance computer used for large number crunching tasks: throughput (in order to get maximum performance), turnaround time (in order to ensure tasks are completed at a useful time)
A multimedia computer (video games, movies...): response time (to ensure smooth playback)
A smartphone: fairness/priority (UI tasks should respond quickly), low scheduling overhead (to conserve battery)
A general-purpose computer on the CIMS network: fairness (each machine has many users)


1.2:
Answers can vary. Here are some items to consider:
A high-performance computer used for large number crunching tasks: Priority (allow important jobs to run), FIFO (lowest overhead, if the machine is only being used by one job at a time)
A multimedia computer (video games, movies...): Priority (give multimedia programs higher priority)
A smartphone: Priority (UI tasks should respond quickly)
A general-purpose computer on the CIMS network: RR (allow all users to fairly use the machine), Stride/Lottery (ticket count can be controlled per-user)


1.3: 
Answers can vary. Here are some items to consider:
A high-performance computer used for large number crunching tasks: RR with a small quantum (wasteful), STCF (starvation for large jobs)
A multimedia computer (video games, movies...): MLFQ (wasted computation), STCF (penalizes long-running multimedia programs)
A smartphone: FIFO (does not pair well with UI tasks)
A general-purpose computer on the CIMS network: FIFO (one user submits a large job, the entire network is unusable for everyone else)



2. virtual memory: warmup
    8     2^8           256 - 1 = 255
    16   2^16 = 64K     64K - 1
    32   2^32 = 4G      4G - 1
    48   2^48 = 256T    256T - 1
    64   2^64 = 16E     16E - 1  (E: Exabyte)


3. virtual memory: warmup II

    Since virtual addresses are 11 bits, and since each address is the
    address of a byte, the virtual address space is 2^{11} bytes, or 2KB, or
    2048 bytes.

4. virtual memory: address translation
	1KB   22    14    10
	2KB   21    13    11
	4KB   20    12    12
	8KB   19    11    13


5. virtual memory: address translation II

    5.1. VA = [ 20 bits  | 40 bits ], so VPN is 20 bits.
    5.2  PA = [ 12 bits  | 40 bits ], so PPN is 12 bits
    5.3  offset is 40 bits (because the page size is 2^{40} bytes)


6. virtual memory: paging

    16   4K   16
    16   8K   8
    32   4K   2^20=1M
    32   8K   2^19=512K
    48   4K   2^36=64G