Total physical ram of the machine, ram modules or ram allocated by the software? The first is not always power of two - a machine with 6GB of ram works just fi

Total physical ram of the machine, ram modules or ram allocated by the software? The first is not always power of two - a machine with 6GB of ram works just fine, the third - it is more convenient to allocate power of 2 sized blocks of ram because this makes the allocation algorithms faster. The second - not sure but I suppose it is more convenient - while there may not be reasons while you cannot have 1023 Mbit block it makes no sense because everything else is based on the power of 2 in computers anyway.