Segmentation vs Paging?
Paging is incidental
Page-data is heterogeneous
Statically Sized
Segments are intentional
Segment data is homogenous
Dynamically Sized
Pure Segmentation
Segment size varies and changesExternal Fragmentation
Also called “Checkerboarding”Swapping large segments for smallResolution: Compaction
MULTICS Implementation
Similar to Multi-Level PagingAddress contains Segment # for tableSegment table holds Segment DescriptorsDescriptor contains page table locationStandard Page Table
Has 218 segments 216 Pages With 36-bit entries234 Total Pages
Pentium Implementation
Local/Global Descriptor TableLocal contains program informationGlobal is OS information3-level Paging (Segment +2-level Virtual)
213 Global + 213 Local (per Program) Segments214 Total Segments per program232 Pages with 32-bit entries246 Total Pages
Pentium Code Descriptor
In-memorySystem or Application segmentType & Protection (Code/Data)Segment Scale (16-bits or all 32?)