MMU: PDR A bit is set for every access

[wfjm]

The PDR A bit is described in the Technical Manual as

A bit (bit 7) - This bit is used by software to determine whether or not
any accesses to this page met the trap condition specified by the Access
Control Field (ACF). (A = I is affirmative). The A bit is used in the
process of gathering Memory Management statistics.

It is set when the page ACF enables an MMU trap, thus for

• ACF=1 and read access
• ACF=4 and any access
• ACF=5 and write access

The w11 currently sets the 'A' bit on any non-aborted access regardless of the ACF value.

No practical impact, the 'A' bit in PDR is a 11/45 11/70 only feature and not used in OS software.