``Stopping RAM access''

[Andrew Duane]

Well, if the system stops accessing RAM, you had better make sure that *all* the instructions you need are already loaded into the L1 and L2 caches. Otherwise you won't be able to turn RAM back on. That would involve carefully preloading everything through use of the system's appropriate PREFETCH calls, locking down the cache lines to make sure nothing else disturbs them, turning off interrupts, and probably more.

To actually turn off RAM, you'd have to power down or otherwise disable the memory controller interface on your board. The procedures for that would be highly platform dependent.


/Andrew
 
> -----Original Message-----
> From: owner-freebsd-hackers at freebsd.org [mailto:owner-freebsd-
> hackers at freebsd.org] On Behalf Of Maslan
> Sent: Tuesday, October 30, 2007 5:02 PM
> To: Jaroszewski Łukasz
> Cc: freebsd-hackers at freebsd.org
> Subject: Re: ``Stopping RAM access''
> 
> > Can anyone give me a clue, how one can ``stop'' system from accessing
> > RAM, and then allow it again?