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My question is how many and what all functional units does the NEON unit on ARM cortex-a8 have? If I have read correctly, the TRM doesn't explicitly say anything about the number of functional units on NEON core of ARM cortex-a8.

nguns
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  • What do you mean by functional units? – auselen Jan 29 '13 at 06:39
  • @auselen ADD, SUB, SHIFT, MUL/ACC, etc. – nguns Jan 29 '13 at 06:58
  • No, the functional units within NEON, how many ADD units, Mul, LOAD units etc. – nguns Jan 29 '13 at 07:18
  • You need to ask your question more clearly, I think. There is one NEON per core afaik and there is one load unit per NEON as well. Neon supports float and integer data but it is inorder and doesn't parallel issue on A8. – auselen Jan 29 '13 at 07:24
  • Why are you interested in such information? – auselen Jan 29 '13 at 07:26
  • Neon can parallel issue, if it's a load/permute combined with a calculation instruction. Anyways, I'm just curious to know, how many functional units of each type are there within the NEON core. I don't think I can put it in a better way than this. – nguns Jan 29 '13 at 07:34
  • This was supposed to be related to software programming, since I wanted to know the number of functional units within a core, so as to use them efficiently, which is required in optimization. Since the TRM din't say about it specifically, I believe this is a valid question. – nguns Jan 29 '13 at 09:54
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    Doing that level of optimization is extremely hard or even may be not possible at all. – auselen Jan 29 '13 at 09:58
  • But that still shouldn't invalidate this question, should it? – nguns Jan 29 '13 at 10:05
  • I didn't down vote or cast a close vote but I think if it is about something you can't really do a difference it makes the question off topic actually. May be you could have asked more clearly to avoid negative attention. – auselen Jan 29 '13 at 10:23
  • sure, thanks @auselen will keep that in mind henceforth. – nguns Jan 29 '13 at 10:29

1 Answers1

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Hopefully picture below from a Cortex-A8 descriptive paper (section 6.2) can help you

Cortex A8 NEON pipeline

auselen
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