Background: Running an offline i7-970 (6-core) machine (Win 7 Home Premium, 64-bit) with 8G memory, using Sonar Plat.  Have performed a number of OS tweaks (recommended in this forum and elsewhere), but after running a project with a number of heavy memory demand VSTs, I noticed my system slowing to an awful crawl, and after looking at the task manager I noticed the memory available was:
a) being reported in correctly (said I only had 4GB)
b) totally used up (and I suspect disk caching was happening).  A LARGE portion was hardware reserved.
 
What I found out:
1) Windows Task Manager has a known issue where it reports available memory incorrectly (but....Resource Monitor will report the correct values).
2) In the BIOS, the RAM memory settings (Advanced BIOS Features) include options for Memory Mirroring (Redundant memory) and Shadowing (Copies firmware contents such as system BIOS, video BIOS, and add-on card BIOS to RAM.).  These settings are done for system memory protection (Redundant) and speed (Shadowing).  What this means is that if you install 8GB, basically as much as half of that memory can be set aside (i.e. mirrored), meaning your system, with 8GB, is basically only using half of that amount, with the other half held in reserve - just sitting there.
 
My question: has anyone disabled these features and seen negative results (crashes, performance, etc.)?    I'm going to do a bit of experimenting tonight (disable these BIOS features) and see what results I get. 
 
We'll see what happens.....

Shadowing is redundant on any current version of Windows (has been since about Windows 95 :-)).

You are running 64bit Win7 (and 64bit Sonar), right?
If you are running 32bit Win7, 4 gigs of ram is the limit for the os.
 

gustabo
You are running 64bit Win7 (and 64bit Sonar), right?
If you are running 32bit Win7, 4 gigs of ram is the limit for the os.
 

 
That's what I was thinking. I was done with 32-bit OS's when I found that out... Otherwise, I've read a bit that it may be possible your motherboard may have a RAM limit (correct me if I'm wrong)

Am running 64 bit OS. My RAM max is 16GB.

I personally don't think you'll have any issues if you turn those features off, but you won't know unless you try. I have a very similar setup, i7/960 6 core with 24GB of RAM and Sonar happily consumes as much memory as it needs.

Whelp!  Huge relief - problem solved!!
 
After searching high and low, I checked everything: OS, attached graphics card demand, memory working, msconfig setup etc.  Youtube blah blah blah....
 
It came down to surfing the MSI (my motherboard maker) website, and downloading the latest BIOS. Flashed the BIOS (a real nail biter!!) via a MS-DOS USB, and I went from having 5GB being "Hardware Reserved" to 15MB "Hardware Reserved". So, even with a really big project loaded, I have 6Gig of RAM sitting there, waiting for tasking!
 
Whew!  Love it when I don't slam into the earth while flying solo!
 
To the music!

Shocking difference and crazy that you had to update your BIOS for that. But great that you solved your issue!

Seriously.  Screw up that operation and the motherboard is toast!  The BIOS (and my machine!) is kinda old.  Never noticed I had an issue until I started loading some heavy sample VSTs (Rhythmology loads a half to whole gig with each program).
 
All'swell!