作者uminchu185 (luke)
看板Grad-ProbAsk
标题Re: [理工] [计组]-清大93 page计算
时间Sun Jan 10 23:17:57 2010
※ 引述《polomoss (小泽)》之铭言：
: Consider a logical address of 2048 pages of 1024 words (4byte) each,
: mapped onto a physical of 64 frames. Assume the smallest memory
: allocation unit is one byte
: a. How many bits in the logical and physical address
: b. one-level page table is used, how many bytes are required by PT
: c. two-level PT is used, and first level table has 32 entries,
: what is the minimal amount of memory required by PT.
: 可以帮我算一下吗?(以及列式)
: 另外题目有点看不懂，是说总共2048个page?
: 每个page有1024个word? 那(4byte)又是指什麽?
: 谢谢
题目说是byte addressing.
一个page size = 1024*4 = 2^12 bytes -> offset = 12bits;
logical space有2^11个pages -> page index = 11bits;
physical space有2^6个frames -> frame index = 6bits;
(1) logical address需11+12 = 23bits; physical address需6+12 = 18bits.
(2) 假设PT entry size = 6bits( 题目没说有哪些特殊位元, 不考虑 ),
PT size = 2^11*6bits = 1.5KB.
(3) outer PT有32个entries -> P1 = 5bits; 因此P2 = 23-5-12 = 6bits,
一个inner PT size = 2^6 * 6bits = 48bytes;
outer PT的size = 32*6bits = 24bytes; 所以答案是24bytes.
(这小题不太确定)
有错请更正~
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