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Computer Systems: A Programmer's Perspective (2nd Edition) [Randal E. Bryant, David R. O'Hallaron] says

A block is a fixed-sized packet of information that moves back and forth between a cache and main memory (or a lower-level cache).

A line is a container in a cache that stores a block, as well as other information such as the valid bit and the tag bits.

  1. I understand that a block is often used as a unit in a disk. Is there some relation between the block used here and a block in a disk? Do they have the same size?

  2. A page frame is a unit in a main memory. What is the relation between a block/line in a cache and a page frame in a main memory? Do they have the same size?

Thanks.

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All of these sizes you ask about are variable, and implementation specific.

No, the use of "block" in this situation is not related to the block size on a permanent storage device. In that case, a block is the smallest amount of bits that can be modified at one time. For example, if you have a block size of 16KB on a filesystem, then no file can take up less than 16KB.

https://stackoverflow.com/questions/8537579/file-system-block-size

I'm not as familiar with the relationship between a cache block and a memory page, but presumably the cache line will be smaller than or equal to the memory page, as a cache is a subset of data from memory.

  • Thanks. A main memory is a "subset" of data from a disk, in the same sense as "a cache is a subset of data from memory". But a page in a main memory is bigger than a block in a disk – Tim Oct 9 '18 at 20:27

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