And that memory access was also the reason a 6502 carefully programmed will have better performance than a 8088 with 5x the clock speed. The first 256 bytes (0 pages) had better access performance.
I'm broadly skeptical that a 6502 outperforms an 8088 at 5x clock speed in practice. Would love to see benchmarks. Certainly I'd expect it to be highly task dependent.
These comparisons have so many variables that they are extremely hard to make accurately.
FTA - I would have guessed that the 8088 is much faster at about the same clock speed, because it has more 16-bit operations and does multiplication and division in hardware.
Does the compiler of the compiler make use of these extra 16-bit operations? How many layers of abstraction does it go through for each of the environments? Does it use DOS interrupts when running on DOS and optimized machine code on CP/M?
These comparisons are strange thought experiments.
Is it still an inaccurate comparison? Sure. But I expected something dramatically different, so I asked.
Not that it matters much, but strictly speaking this is true only for the PAL version.
On the Dhrystone 1.0 micro-benchmark, a C64 is ~36/s, whereas the PC/XT models tested (basically same as the original PC) are more like 300+/s.
That said, any 16-bit optimizations the 8088's compiler could take advantage of, well, that's fair game.