[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-users] 4GB memory installed, 3.5GB shown (Xen 3.2 + PAE)
Wouter de Geus schrieb: > > Hello, Hi, > > > > I have recently upgraded one of my machines, both in hardware and Xen version. > > In the old situation it had 3GB of memory and Xen 3.1, worked like a charm. > > After upgrading it has 4GB of memory and Xen 3.2. [...] Same thing here. I have a tyan S5112 which has 4 GB phys. RAM installed however the max. mem. size the system can address is limited to 4GB. PAE doesn't work. 64 bit systems don't need PAE. They can address all of the RAM directly. The PCI address space lies in the system addressable space in the upper ~768 MB, starting somewhere at 3.3 GB. The actual beginning may be a bit different, depending on the installed components, BIOS/settings, etc. If PAE (here I mean hardware support for PAE, which includes chipset function) is available then the physical memory which collides with the PCI addr range is remapped to another address, normally beginning somewhere at 4096MB. However if PAE support isn't available, then the last ~768MB of RAM are hidden. Otherwise it would be impossible to address any device in the system because of address space collision between the virtual PCI address range and physical memory address range. The exact specifics of the chipset and addressable memory are noted in the manual of your mainboard. As a rule, I don't buy/get any hardware with max mem size equal to the mem size I intend to install. Hope this could clear some things for you. Regards, Dimitri Puzin aka Tristan-777 Attachment:
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