Total System RAM Estimation

[npnw]

Dave,

These are probably calling a bios routine. Then subtracting the reserved space.

Here is a link to some of the pheonix bios stuff.  This would give you a more accurate byte count of memory.

http://www.google.ch/patents/US6697920

if you go down a ways, it will show you the umb memory block reserved space. You would then take the total memory, subtract all the UMB and this would give you memory above 1 mb. Then you would have to do something for memory allocation below, 1 mb, don't remember where that is, but you get the picture.   They would allocate below 1 mb, then move it to above 1 mb after booting into ____ mode on the processor.  NOt sure if they cleaned that up below the 1 mb limit. 

Hope this helps.

NPNW

[fearless]

Had a look at these videos from Mark Russinovich from that channel9 website:

Mysteries of Memory Management Revealed,with Mark Russinovich (Part 1 of 2): https://channel9.msdn.com/events/TechEd/NorthAmerica/2011/WCL405
Mysteries of Memory Management Revealed,with Mark Russinovich (Part 2 of 2): https://channel9.msdn.com/events/TechEd/NorthAmerica/2011/WCL406

Quite informative and gives a good overview of his vmmap and rammap tools