The correct answer is: A. Through internal unified cache.
The 80486 processor has an internal unified cache that is shared by both instructions and data. This cache is organized as a four-way set-associative cache with a line size of 16 bytes. The cache is divided into two halves, one for instructions and one for data. Each half of the cache has a 64-entry tag array and a 64-entry data array.
The cache is used to store instructions and data that are currently being accessed by the processor. When the processor needs to access an instruction or data, it first checks the cache. If the instruction or data is found in the cache, it is read directly from the cache. If the instruction or data is not found in the cache, it is fetched from main memory.
The use of a cache improves the performance of the processor by reducing the number of times that the processor needs to access main memory. This is because main memory is much slower than the cache.
The following are the brief descriptions of each option:
- Option A: Through internal unified cache. This is the correct answer. The 80486 processor has an internal unified cache that is shared by both instructions and data.
- Option B: Through external unified cache. This is incorrect. The 80486 processor does not have an external unified cache.
- Option C: Through external cache. This is incorrect. The 80486 processor does not have an external cache.
- Option D: Through multiple caches. This is incorrect. The 80486 processor has a single internal unified cache.