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Comment by sytse | Hacker News Reader

I looked into the differences between the 8086 and 8088 because the 8086 was selected for most designs when the 8088 was already available.

Turns out the 8088 has less compute power. I think all Intel chips since than have higher numbers if they are more powerful, not if they are more recent.

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8088 is simply a 8-bit version of the 8086, thus the "8" in 8088. It was developed because the 16-bit 8086 was somewhat ahead of its time - back then, everything in existence - PCBs, interface and driver chips, backplanes, connectors, etc - was still centered around the 8-bit data bus and it was impractical to redesign them. Until they start becoming obsolete, allowing 16-bit successors to take over gradually.

I'm not sure what you're saying. The 8086 was introduced in 1978, while the 8088 was introduced in 1979. The 8088 is essentially the same as the 8086, except the external bus is 8 bits instead of 16 bits, which reduced system costs. The original IBM PC selected the 8088, not the 8086.

The Intel chip numbers are all over the place. For instance, the 8048 series had parts ranging from the 8020 to the 8749; the "7" indicated EPROM.

Contrary to what the others are saying, 8086 and 8088 have more differences than just bus size. Certain instruction have different timings, and as I vaguely remember, pipeline depth was also different.

The effect of the 8-bit bus and prefetch queue are described in detail here:

http://www.jagregory.com/abrash-black-book/#the-8-bit-bus-cy...

The 8086 and 8088 CPUs differ essentially from one another by their respective data bus widths (the 8086 uses a 16-bit data bus, and the 8088 uses an 8-bit data bus). The Execution Unit for each processor is identical. The Bus Interface Unit for the 8086 incorporates a 16-bit data bus and a 6-byte instruction queue whereas the 8088 incorporates an 8-bit data bus and a 4-byte instruction queue.

See the iAPX 86,88 User's Manual http://www.bitsavers.org/components/intel/_dataBooks/1981_iA...

You contradict yourself, when you say "differ essentially from one another by their respective data bus widths" and "8086 incorporates a 16-bit data bus and a 6-byte instruction queue whereas the 8088 incorporates an 8-bit data bus and a 4-byte instruction queue.". In a sense 8088 has shorter pipeline. Shorter pipeline makes optimization techniques for 86 and 88 different, irrespective of the bus width - I mean, even if you slap 16 bit bus to 88, without changing the queue size, most efficient optimizations would still be different between these 2 CPUs.

I'm literally quoting from page 4-1 of the Intel 8086/8088 manual.

And how the fact that you are quoting from some manual contradicts the fact that speed is different because of different pipeline depth?

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