Model vs. ARM

This note gives a complete comparison of our model with ARM hardware. As illustrated by the numerous tests of the table “Forbidden by model and observed”, ARM hardware contradicts our model. Refer to this companion page for an analysis.

We first provide a selection of some behaviours from the complete “Forbidden by model and observed” table. This selection first presents the test CoRR1, which is the archetype of the read-after-read hazard anomaly. We also show the more sophisticated CO-RSDWI, which includes CoRR1 as a sub-test. One may notice that our runs of these two tests demontrate observation of the read-after-read hazard anomaly on all tested machines.

The test MP+dmb+fri-rfi-ctrlisb, observed on Qualcomm APQ8060 only, is claimed by ARM designers to be legal. Although the very test MP+dmb+fri-rfi-ctrlisb is not observed on the more modern APQ8064, we have observed similar behaviours on this system. Some examples of those are LB+data+fri-rfi-ctrl, LB+data+data-wsi-rfi-ctrl, S+dmb+fri-rfi-ctrl. We logically think that those similar behaviours should also be considered legal.

Other tests are examples of invalid behaviours that are observed much less often and only on (quite ancient) quad-core systems Tegra3 and Exynos4412. We think those should not be considered legal — See the companion document for details on those “bizarre” tests. We here present two such behaviours: a coherence anomaly MOREDETOUR0052, and a violation of the MP+dmb+ctrlisb idiom included in the more complex MP+dmb+pos-ctrlisb+BIS.

There are 8 such tests
CoRR1ForbidNo, 10M/102GNo, 928k/12GNo, 87/24GNo, 249k/3.9GOk, 0/14GOk, 0/8.3GNo, 7.7M/18GNo, 1.0M/11GOk, 0/6.3GNo, 612/5.4G
  Forbid invalidatedForbid invalidatedForbid invalidatedForbid invalidated  Forbid invalidatedForbid invalidated Forbid invalidated
CO-RSDWIForbidNo, 4.4M/33GNo, 204/60MOk, 0/2.2GNo, 40k/1.6GNo, 1/3.5GNo, 74k/5.0GNo, 204k/3.5GNo, 120k/6.9GNo, 12k/5.6GNo, 3.9M/4.5G
  Forbid invalidatedForbid invalidated Forbid invalidatedForbid invalidatedForbid invalidatedForbid invalidatedForbid invalidatedForbid invalidatedForbid invalidated
MP+dmb+fri-rfi-ctrlisbForbidNo, 153k/193GOk, 0/44GNo, 153k/10GOk, 0/9.0GOk, 0/14GOk, 0/8.3GOk, 0/62GOk, 0/34GOk, 0/6.3GOk, 0/4.7G
  Forbid invalidated Forbid invalidated       
LB+data+fri-rfi-ctrlForbidNo, 123k/26GOk, 0/1.4GOk, 0/2.4GOk, 0/2.6GOk, 0/3.4GOk, 0/2.5GOk, 0/4.8GOk, 0/4.1GNo, 123k/4.6G
  Forbid invalidated        Forbid invalidated
LB+data+data-wsi-rfi-ctrlForbidNo, 7.4k/20GOk, 0/820MOk, 0/1.6GOk, 0/1.4GOk, 0/2.7GOk, 0/1.7GOk, 0/4.8GOk, 0/2.5GNo, 7.4k/4.2G
  Forbid invalidated        Forbid invalidated
S+dmb+fri-rfi-ctrlForbidNo, 373k/26GOk, 0/1.3GOk, 0/2.4GOk, 0/2.6GOk, 0/3.4GOk, 0/2.4GOk, 0/4.8GOk, 0/4.1GNo, 373k/4.6G
  Forbid invalidated        Forbid invalidated
MOREDETOUR0052ForbidNo, 9/33GNo, 7/3.4GNo, 2/24GOk, 0/3.1GOk, 0/2.3G
  Forbid invalidated     Forbid invalidatedForbid invalidated  
MP+dmb+pos-ctrlisb+BISForbidNo, 81/37GNo, 81/13GOk, 0/18GOk, 0/3.1GOk, 0/2.3G
  Forbid invalidated     Forbid invalidated   

This document was translated from LATEX by HEVEA.