Problem 6. Nowadays the virtual address is much larger (64 bits) than the physical address space (e.g., on my MacBook, 35 bits). However, in "the old days" (early 80's), it could be the other way around. For example, on a PDP11/70 minicomputer runing UNIX, each process had a 64 KB (16 bit) virtual address space, while the machine had a 2 Megabyte physical memory. The virtual address space was divided into 8 pages of 8 Kbytes each. Thus each process had a page table with 8 entries. a. How big (how many bits) were the physical addresses in this system? b. How many high-order bits of the virtual address made up the virtual page number? c. How many bits are the offset in the page, and the physical page slot number? d. In the table below, you are given virtual-to-physical address mappings. For each one, say what page table entry was used, and what it contained, i.e., what the corresponding virtual page number (VP#, i.e., index into the page table) and physical page number (PP#, i.e., high-order bits of the physical address) were. Virt. Address Phys. Address VP# PP# Ох4f37 Ox06ef37 Ox25b4 Ox1085b4 Oxa720 Ox19c720 Охd158 Ox17f158 e. What advantages does virtual memory, i.e., making virtual and physical addresses independent, offer in this situation?
Problem 6. Nowadays the virtual address is much larger (64 bits) than the physical address space (e.g., on my MacBook, 35 bits). However, in "the old days" (early 80's), it could be the other way around. For example, on a PDP11/70 minicomputer runing UNIX, each process had a 64 KB (16 bit) virtual address space, while the machine had a 2 Megabyte physical memory. The virtual address space was divided into 8 pages of 8 Kbytes each. Thus each process had a page table with 8 entries. a. How big (how many bits) were the physical addresses in this system? b. How many high-order bits of the virtual address made up the virtual page number? c. How many bits are the offset in the page, and the physical page slot number? d. In the table below, you are given virtual-to-physical address mappings. For each one, say what page table entry was used, and what it contained, i.e., what the corresponding virtual page number (VP#, i.e., index into the page table) and physical page number (PP#, i.e., high-order bits of the physical address) were. Virt. Address Phys. Address VP# PP# Ох4f37 Ox06ef37 Ox25b4 Ox1085b4 Oxa720 Ox19c720 Охd158 Ox17f158 e. What advantages does virtual memory, i.e., making virtual and physical addresses independent, offer in this situation?
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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Transcribed Image Text:Problem 6. Nowadays the virtual address is much larger (64 bits) than the physical address space
(e.g., on my MacBook, 35 bits). However, in "the old days" (early 80's), it could be the other
way around. For example, on a PDP11/70 minicomputer runing UNIX, each process had a 64 KB
(16 bit) virtual address space, while the machine had a 2 Megabyte physical memory. The virtual
address space was divided into 8 pages of 8 Kbytes each. Thus each process had a page table with
8 entries.
a. How big (how many bits) were the physical addresses in this system?
b. How many high-order bits of the virtual address made up the virtual page number?
c. How many bits are the offset in the page, and the physical page slot number?
d. In the table below, you are given virtual-to-physical address mappings. For each one, say what
page table entry was used, and what it contained, i.e., what the corresponding virtual page
number (VP#, i.e., index into the page table) and physical page number (PP#, i.e., high-order
bits of the physical address) were.
Virt. Address Phys. Address VP# PP#
Ох4f37
Ox06ef37
Ox25b4
Ox1085b4
Oxa720
Ox19c720
Oxd158
Ox17f158
e. What advantages does virtual memory, i.e., making virtual and physical addresses independent,
offer in this situation?
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