CODEWITHSUNDEEP
x86cpu-architecturex86-16
Priyanshul Govil
Priyanshul Govil

Reputation: 589

Does 8086 initiate a 1-byte code fetch when there's only 1 byte left in the prefetch queue?

I know that the 8086 architecture has a 6-byte prefetch queue.

My questions is, does the Bus Interface Unit fetch another byte-sized instruction as soon as one instruction is moved to the Execution Unit and space is free in the queue? Or does it wait for some specific number of bytes to be freed up before it starts fetching again?

Upvotes: 3

Views: 315

Answers (1)

Priyanshul Govil
Priyanshul Govil

Reputation: 589

The BIU is programmed to fetch a new instruction whenever the queue has room for one (with the 8088) or two (with the 8086) additional bytes.

source: http://ee.sharif.edu/~sakhtar3/articles/8086/8086%20Architecture.htm

Upvotes: 4

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