[Info-vax] yet another sys$qiow question

[David Froble]

Craig A. Berry wrote:
> On 8/21/15 8:41 AM, Johnny Billquist wrote:
> 
>> What is wrong with checking the IOSB before the I/O completes? There is
>> absolutely nothing wrong with that. And if it is non-zero, it means the
>> I/O already have completed, so there is no point in waiting, since it
>> will return immediately.
> 
> Until the I/O completes, the status of the IOSB is undefined. Show me
> where there is a guarantee that if one longword of the IOSB has been
> written, that the other longword has also been written, i.e., that the
> entire IOSB is written atomically or in a single instruction. Without
> that guarantee, non-zero does not mean complete.

Yes.  Exactly that.  Remember what happens when you ass-u-me.