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CSC 711 Cram Sheet - last hour

Numbers to memorise

• Page 4 KB = 2^12; offset 12 bits; page number 20 bits.
• 2^20 = 1,048,576 PTEs; x4 B = 4 MB flat table.
• i386 split: 10 (dir) - 10 (table) - 12 (offset); PTE 32 bits.
• System V block 1 KB; FFS block 4 KB.

Mnemonics

• Coffman: M-H-N-C = Mutual exclusion, Hold-and-wait, No preemption, Circular wait.
• FFS wins: C-B-F-B = Cylinder groups, Big blocks, Fragments, Bitmaps.
• PTE bits bit0 up: P R/W U/S PWT PCD A D PAT G.
• I/O layers: hardware -> interrupt -> driver -> device-independent -> user-level.

One-line contrasts

• FAT = linked chain; inode = indexed.
• System V separates inodes/data (long seeks); FFS co-locates (locality).
• Programmed I/O = per byte; DMA = per block, one interrupt.
• Monolithic = one privileged space; microkernel = user-space servers over IPC.
• Prevention = break a condition; avoidance = Banker's safe state.
• Non-pre-emptive = no Running->Ready; pre-emptive = can remove from CPU.

Scheduling

• FCFS (batch), RR (interactive), Timeslice Priority (importance/real-time), MLFQ (general mixed).
• Watch: convoy effect, starvation, aging, priority inversion, quantum size.

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