Model vs. new generation ARM processors

This note presents experiments on new generation ARM processors, that is on CortexA15 designs.

  1. Apple A6X (Apple new iPad, or iPad 4), based on Apple own “Swift” design;
  2. Samsung Exynos5250 (Nexus 10 tablet), a dual-core CortexA15;
  3. Samsung Exynos5410 (ODROID-XU development board), a quad-core CortexA7–CortexA15.

Notice that we classify Apple Swift as being similar to CortexA15, which it may not be. However, all chips were released at similar times.

Saliant points are:

  1. Although ARM note on the read-after-read hazard anomaly applies to Cortex-A9, we still observe a few instances of this anomaly on all “new generation” systems, as illustrated by the table “Invalid behaviours”.
  2. As illustrated for instance by the tests LB and  S+dmb+po in table “Unseen behaviours”, new generation processors apparently do not allow read-to-write reordering.

This document was translated from LATEX by HEVEA.