XP 32 bit Memory
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From: John John - MVP on 7 Dec 2009 16:43 dennis wrote: > John John - MVP wrote: > >> AWE, only for the applications own use, you can't develop a memory >> manager around this, the kernel will not allow this to manage other >> processes' memory. On 32-bit systems AWE will only be able to access >> RAM above the 4GB barrier if the operating system is PAE capable, >> 32-bit XP can't do it. Few applications are AWE capable, this is >> mostly reserved for large database programs and other such applications. >> > > I'm not talking about AWE, but about mapping "device" space (physical > memory). That way you can use memory above 4G also in 32bit XP. > > XP supports PAE. Its own memory manager just doesn't allow access to > memory above 4G. XP supports PAE for DEP only, drivers and applications can't access the memory above the 4GB barrier. From what I understand memory above the 4GB barrier was available with PAE when XP was released but too many drivers were misbehaving and causing BSODs so Microsoft decided to put an end to this in SP1. I know that a certain RAM disk can apparently make use of the memory above the 4GB barrier, I guess this is what you mean by "device space". Although the RAM drive can map the space for use as temporary storage for other applications the other applications still cannot use this for their process space, the memory manager does not permit any applications to directly manage other processes' space. Other than snake oil memory memory optimizers there are no third party memory managers for NT operating systems. John
From: dennis on 7 Dec 2009 17:01 John John - MVP wrote: > I know that a certain RAM disk can apparently make use of the memory > above the 4GB barrier, I guess this is what you mean by "device space". With device space I mean this: http://msdn.microsoft.com/en-us/library/ms801998.aspx And yes, some ram-disks uses that to use memory above 4G. > Although the RAM drive can map the space for use as temporary storage > for other applications the other applications still cannot use this for > their process space True, you need a bit more to use that kind of memory for other than data storage.
From: J. P. Gilliver (John) on 7 Dec 2009 20:39 In message <ezxKsI4dKHA.1592(a)TK2MSFTNGP06.phx.gbl>, dennis <1(a)1.invalid> writes: >John John - MVP wrote: > >> AWE, only for the applications own use, you can't develop a memory >>manager around this, the kernel will not allow this to manage other >>processes' memory. On 32-bit systems AWE will only be able to access >>RAM above the 4GB barrier if the operating system is PAE capable, >>32-bit XP can't do it. Few applications are AWE capable, this is >>mostly reserved for large database programs and other such applications. >> > >I'm not talking about AWE, but about mapping "device" space (physical >memory). That way you can use memory above 4G also in 32bit XP. > >XP supports PAE. Its own memory manager just doesn't allow access to >memory above 4G. When I suggested a memory manager, I wasn't talking about going beyond the 4G limit, I was talking about accessing the RAM within the 4G but beyond where hardware sits on some machines, i. e. using non-contiguous memory. -- J. P. Gilliver. UMRA: 1960/<1985 MB++G.5AL-IS-P--Ch++(p)Ar(a)T0H+Sh0!:`)DNAf ** http://www.soft255.demon.co.uk/G6JPG-PC/JPGminPC.htm for ludicrously outdated thoughts on PCs. ** Reality and talent shows lack honesty. They manipulate the viewer with mawkish stories. Contestants turn tragedies into qualifications. - Sean Lock, in Radio Times, 20-26 June 2009
From: dennis on 7 Dec 2009 21:11 J. P. Gilliver (John) wrote: > When I suggested a memory manager, I wasn't talking about going beyond > the 4G limit, I was talking about accessing the RAM within the 4G but > beyond where hardware sits on some machines, i. e. using non-contiguous > memory. That is a hardware problem that you cannot solve with software. That is why the memory remapping function were invented.
From: John John - MVP on 7 Dec 2009 21:48
dennis wrote: > John John - MVP wrote: > > >> I know that a certain RAM disk can apparently make use of the memory >> above the 4GB barrier, I guess this is what you mean by "device space". > > With device space I mean this: > http://msdn.microsoft.com/en-us/library/ms801998.aspx Thanks for the link. In one of his blogs Mark Russinovich said that "...problematic client driver ecosystem led to the decision for client SKUs to ignore physical memory that resides above 4GB, even though they can theoretically address it." My understanding about this is that while (some of) the server versions can do this the whole point of limiting memory access below 4GB on clients with PAE was to specifically prevent drivers from playing in the upper memory arena. So now I'm not sure what to think... http://blogs.technet.com/markrussinovich/archive/2008/07/21/3092070.aspx Mark's Blog : Pushing the Limits of Windows: Physical Memory John |