I have a Intel Core i7 920 with 12GB (6x2GB) of Corsair Triple Channel RAM mounted on an EVGA X58 motherboard. I recently noticed that my usable memory was not always synonymous with the amount installed i.e. 12.0 GB (7.99 usable), 12.0 GB (3.99 usable) etc. I've read a lot about this issue and there seem to be several different causes and solutions.
I found after dozens of boots when my computer has been powered down for an extended period of time the usable memory is always lower than the actual installed. However, if I power down and reboot after the computer has had a bit of warmup time the actual memory and usable are the same.
NOTE: Restarting will not cause this effect. Only a complete shutdown and reboot does this.
To date 11/4/2012 I have:
1.) Removed the memory and installed individually to test for bad rail or bad memory stick
2.) Cleaned each stick of memory three times with alcohol solution
3.) Updated all Hardware and BIOS
4.) Slammed my head against the desk once or twice
Any suggestions would be appreciated. I can provide more information as needed.