[Info-vax] yet another sys$qiow question

[Bob Gezelter]

For those without an Alpha Architecture manual at hand:

5.6.3  Implied Barriers
There are no implied barriers in Alpha. If an implied barrier is needed for functionally correct access to shared data, it must be written as an explicit instruction. (Software must explicitly include any needed MB, WMB, or CALL_PAL IMB instructions.) Alpha transitions such as the following have no built-in implied memory barriers:
* Entry to PALcode
* Sending and receiving interrupts
* Returning from exceptions, interrupts, or machine checks
* Swapping context
* Invalidating the Translation Buffer (TB)

- Bob Gezelter, http://www.rlgsc.com