Re: CAS?

[Matt Thomas <matt%3am-software.com@localhost>]

On Nov 8, 2010, at 10:34 AM, der Mouse wrote:

>> [...], or if it might be worth some work to rewrite these to as far
>> as possible use VAX primitive instructions for the needs instead.
> 
> Offhand, I would guess that whoever did it looked for a few things like
> compare-and-store, ll/sc, test-and-set, thought the VAX didn't have any
> of them, and went the slow route, not discovering things like BBCCI and
> INSQHI.  The VAX isn't _quite_ old enough to lack such things entirely,
> but it _is_ old enough to have preliminary forms of them rather than
> the forms more recent processors have settled on. :-)

I did them and I am fully aware of what interlocked instructions the 
VAX has.  Note BBxxI are used but they must be used at IPL_HIGH
to avoid problem with interrupts causing a deadlock.  

The interlocked queue instructions just aren't that useful since the
MI code can't easily use them.

ADAWI would be great to use except it's only operates on 16 bit 
quantities.

> But, since I'm not that whoever, I don't really know.  I may be
> maligning someone unjustly with that suspicion.

Yes, you may.