Hi Experts,
A8 is meant for single core and A9 is for multi-core based.
Consider in case of SoC is build with single core of A9 and A8 how we could compare both in terms of some metrics/parameters like power/speed ?
For most code Cortex-A9 will be faster, as it has a tighter integration of scalar floating point as well as general purpose out-of-order execution for the integer core, making it better at hiding the overheads of cache misses and other stalls. It is also worth noting that there are quite a few revisions of the Cortex-A9 - the latest (r4p1) is significantly improved over the early revisions (bigger branch predictor, bigger TLBs, better L1 cache prefetcher).
Cortex-A8 can be better at some NEON heavy code - it can dual issue many (but not all) combinations of the SIMD instructions, whereas Cortex-A9 is generally single issue for SIMD, although this is offset by the fact that Cortex-A9 has a higher top frequency. For most real code this isn't too much of a restriction, and the NEON is still much faster than not using it.
Remember that ARM just licenses the core designs to other companies to manufacture into whatever chips they can imagine, so it is possible to get a slow and inefficient new CPU and a fast and efficient old one. Manufacturing choices (silicon process, top frequency, number of cores, etc) can make a huge difference to the performance and power characteristics of a design, even if an identical CPU design is used in both.
If you are buying off the shelf parts, then many Cortex-A9 designs are newer than Cortex-A8 based parts so will also generally benefit from newer process manufacturing technology. This will help performance and energy efficiency; although this isn't really down to the IP itself, it can play a huge factor in design performance, so must be considered.
HTH, Pete
The Cortex-A8 is I think the oldest member of the Cortex-A family and has slipped from their current portfolio as something else will always be better for anything (though I'm sure they'll always licence you anything if you ask!). As you say a decision is complicated, but you'll have a minimum speed requirement and a power requirement and can work from there. Wikipedia have a little table which gives some basic details of the differences between the cores but doesn't indicate their design maximum frequencies or power.
Comparison of ARMv7-A cores - Wikipedia, the free encyclopedia
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