Guardiamo un'attimo questa figura, presa dal tool System Information sotto VPC:
perchè le due quantità sono diverse?
Quoto una risposta trovata su un NG degli MCT e fornita da Paul Adare [MVP - Windows - Virtual Machine]:
There are a couple of ways an app can request the total amount of RAM
installed, query the BIOS or query the motherboard for the size of each
installed memory module and then add up what it returned.
Since you can have odd amounts of memory in a guest (527 Mb for example)
the second method is hard to implement in a virtual machine product.
Querying the BIOS from inside the guest will report the correct amount,
but if an app queries the motherboard it reports 8 modules of 8 Mb each.
Non si finisce mai di imparare... 