What does the word UNPREDICTABLE exactly mean and what is its effect on the system?

Hi, In many of ARM documentation result of operations are reported as unpredictable in some situations. For example, "If the system includes the Security Extensions, accesses to CNTVOFF from Secure Monitor...
What does the word UNPREDICTABLE exactly mean and what is its effect on the system?

Hi, In many of ARM documentation result of operations are reported as unpredictable in some situations. For example, "If the system includes the Security Extensions, accesses to CNTVOFF from Secure Monitor...
What's the purpose for WACK and RACK for ACE and what's the relationship with WVALID and RVALID ?

Hi, From hardware perspective, what's the purpose of WACK and RACK and how does it affect the ACE protocol ? I can see that the specification says the master issues these two signals to indicate to...
What's the purpose for WACK and RACK for ACE and what's the relationship with WVALID and RVALID ?

Hi, From hardware perspective, what's the purpose of WACK and RACK and how does it affect the ACE protocol ? I can see that the specification says the master issues these two signals to indicate to...
What are hints?

What does it mean that an instruction is a hint instruction, like NOP, YIELD and WFE? I haven't found any explanations in ARM Architecture Reference Manual, ARMv7-A and ARMv7-R edition, Issue C. ...