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Ken Shirriff

Intel introduced the 8088 processor in 1979. IBM selected the 8088 for the IBM PC, a moment in computer history that ensured the dominance of Intel and x86.

To improve performance, the 8088 prefetched instructions. Let's look at the prefetch circuitry inside the 8088... 1/12
23 March at 16:42 | Open on oldbytes.space
3 comments
Ken Shirriff

Modern processors cache megabytes of data so it can be accessed without waiting on slow memory. The 8088's prefetch queue held just 4 bytes, still enough for a substantial performance boost. When memory was idle, the 8088 would load upcoming instructions into the queue. 2/12

23 March at 16:43 | Open on oldbytes.space
Ken Shirriff

The queue was implemented with four registers, along with two hardware pointers indicating the next read position and the next write position. Here's how the queue looks with two bytes (blue) in the queue. 3/12
23 March at 16:43 | Open on oldbytes.space
Onno Bos :cybersec: :verified:
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