cache architecture

Question

I have a 2 way associative cache that stores 2 bytes of data in each cache line.

issuing the following sequential write commands:

address | data

xxxx11011 | 1
yyyy11010 | 2
zzzz11011 | 3

What will be the state of the cache?

I think it will be this:

column 1
tag | index | data
zzzz | 1101 | 0x0300

column 2
tag | index | data
yyyy | 1101 | 0x0002

Answer 1

There are many possibilities. It depends on what the cache is made for. For a database like google, it will store the "most used" records. On a small sequential audio-buffer the cache will work as FIFO (first in first out). For sending data tought serial port it could be recommended to use LIFO.

Here are some small informations: Cache methodes

Regards

Answer 2

First, you have selected the wrong answer as the solution. cache replacement policies are important, but not in this specific example. Second, you should let us know the number of entries in the case, so that we can answer this question correctly. Third, index is not stored in caches at all. tag, data, coherence bits, replacement bits are stored (and a few other bits, depending on implementation). Fourth, there is no terminology called column. we call it "way". Now the answer of your question: I assume that there are 2^5=32 entries in the cache. In this case this is what we get:

....             way-1               way-2
in entry #11010: tag: yyyy, data: 2; old tag and data
in entry #11011: tag: xxxx, data: 1; tag: zzzz, data: 3
....

Please note that content of ways are interchangeable. So what I mean is that

....             way-1               way-2
in entry #11010: tag: yyyy, data: 2; old tag and data
in entry #11011: tag: zzzz, data: 3; tag: xxxx, data: 1
....

is also correct.