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The exact definition of outer and inner in ARMv7

Jaeyong Yoo

Hello,

I'm reading ARMv7 architecture reference manual and there are the following keywords:

  • outer cacheable
  • inner cacheable
  • outer sharable
  • inner sharable

It looks like that outer/inner cacheable means that a region of memory can be cached in L1 (inner) or L2 (outer).

What I don't understand is the sharability.

According to the manual, it says inner is sharable inside a cluster and outer is sharable among clusters.

Here, what does cluster mean? It looks like a group of cores, but I'm failed to find exact reference about these.

Any help would be appreciated.

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  • 0 in reply to Peter Harris

    Thanks!! I have checked the ACE spec: IHI0022E_amba_axi_and_ace_protocol_spec -> Figure C1-4 Example system using shareability domains.

    Finally, I got the point: "Iinner/outer have different meaning when they come to shareable/cacheable". :-)

    Noname.jpg

    When comes to cachable, inner/outer mean how many caches would be enabled. (L1 would be always in inner, L2 might be inner or outer)

Reply
  • 0 in reply to Peter Harris

    Thanks!! I have checked the ACE spec: IHI0022E_amba_axi_and_ace_protocol_spec -> Figure C1-4 Example system using shareability domains.

    Finally, I got the point: "Iinner/outer have different meaning when they come to shareable/cacheable". :-)

    Noname.jpg

    When comes to cachable, inner/outer mean how many caches would be enabled. (L1 would be always in inner, L2 might be inner or outer)

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