[Info-vax] QIO Writes to a mailbox

[Steve Bainbridge]

Hi,

I have a very simple question, but when looking at the Alpha internals
manual and talking to colleagues the answer does not seem so obvious.

We have some old code that issues a QIO WRITEVBLK to a mailbox - the
return code from the QIO is normal. Another process reads the mailbox
and never gets the message - this only happens very rarely.
Unfortunately the writer does not check or report what value the IOSB
returns and I need to try and understand why these messages are
getting lost. I can't reproduce this on our test systems and I can't
easily install updated diagnostic code onto these production systems.

The question I have is when is the data pointed to by P1 (in the QIO
call) actually copied ? It is always done within the QIO routine or is
it just scheduled to be done in the QIO call ? Can I re-use the buffer
pointed to by P1 immediately after the call to the QIO ?

Regards,
Steve