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Thread ID: 105845 2009-12-16 07:14:00 Windows 4GB RAM patch for 32bits, real? CCF (6760) Press F1
Post ID Timestamp Content User
840140 2009-12-16 07:14:00 Hey ya all

Came across a patch, actually saw it on a friends pc, that allows 32bit OS to see and use ram that are beyond the traditional 3GB limitation that 32bit OS is known for . The patch appears to work by modifiying certain registry keys and possibly even some things in the bios .

I was wondering is such thing even possible? Even though Im seeing it, I just thought maybe it could just be a display hack or number hack, where in reality the max ram allowed in 32bit OS is still 3GB

My understanding is that the 3GB limitation is an actual windows 32bit architecture limitation, hence regardless of what is done to the reg or even the bios it is only able to use 3GB of ram, even though it may well be able to see more than 3GB .

But then again the registry is the heart of the OS, so I guess anything is possible .

Any comments?
CCF (6760)
840141 2009-12-16 07:23:00 Yes it can be done, search MS.com.
:)
Trev (427)
840142 2009-12-16 07:36:00 Hey ya all

Came across a patch, actually saw it on a friends pc, that allows 32bit OS to see and use ram that are beyond the traditional 3GB limitation that 32bit OS is known for. The patch appears to work by modifiying certain registry keys and possibly even some things in the bios.

I was wondering is such thing even possible? Even though Im seeing it, I just thought maybe it could just be a display hack or number hack, where in reality the max ram allowed in 32bit OS is still 3GB

My understanding is that the 3GB limitation is an actual windows 32bit architecture limitation, hence regardless of what is done to the reg or even the bios it is only able to use 3GB of ram, even though it may well be able to see more than 3GB.

But then again the registry is the heart of the OS, so I guess anything is possible.

Any comments?

Basically most modern processors support a feature called PAE, Physical Address Extension which allow the operating(provided that it supports it) to overcome the 32bit architechtural limit of 4gb of RAM to be utilised.

The reason you can't utilise more than 4gb is a licensing issue rather than an architectural one

Read this:
www.geoffchappell.com

Its long, but very comprehensive and should answer all questions about PAE.

Blam
Blam (54)
840143 2009-12-16 07:50:00 I don't see how this could be done via changes in registry or BIOS, it would require a kernel (the real heart of an OS) with special support for addressing more than 4gig of memory (some of this address space is taken by system devices and video card). Though I understand you can enable a pae kernel with XP via modification of the boot.ini the general consensus seems to be that this kernel still does not support above 4gig addressing, unlike Server 2003 x32. SaAB (1292)
840144 2009-12-16 08:04:00 The reason you can't utilise more than 4gb is a licensing issue rather than an architectural one

Mark Russinovich has a slightly different take on it here:
. technet . com/markrussinovich/archive/2008/07/21/3092070 . aspx" target="_blank">blogs . technet . com

The key bits are:
"However, by the time Windows XP SP2 was under development, client systems with more than 4GB were foreseeable, so the Windows team started broadly testing Windows XP on systems with more than 4GB of memory . "

"What they found was that many of the systems would crash, hang, or become unbootable because some device drivers, commonly those for video and audio devices that are found typically on clients but not servers, were not programmed to expect physical addresses larger than 4GB . As a result, the drivers truncated such addresses, resulting in memory corruptions and corruption side effects . Server systems commonly have more generic devices and with simpler and more stable drivers, and therefore hadn't generally surfaced these problems . The 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 . "

cheers
W
waldok (15185)
840145 2009-12-16 09:22:00 Windows 7 x86 will see 4Gb and even report it, however addressing limitation of 32bit will NOT use the full 4Gb SolMiester (139)
840146 2009-12-16 09:33:00 Mark Russinovich has a slightly different take on it here:
blogs.technet.com

The key bits are:
"However, by the time Windows XP SP2 was under development, client systems with more than 4GB were foreseeable, so the Windows team started broadly testing Windows XP on systems with more than 4GB of memory."

"What they found was that many of the systems would crash, hang, or become unbootable because some device drivers, commonly those for video and audio devices that are found typically on clients but not servers, were not programmed to expect physical addresses larger than 4GB. As a result, the drivers truncated such addresses, resulting in memory corruptions and corruption side effects. Server systems commonly have more generic devices and with simpler and more stable drivers, and therefore hadn't generally surfaced these problems. The 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."

cheers
W

Yes-that is also the other reason behind this..

IMO Microsoft just didn't bother trying to fix PAE...
Blam (54)
840147 2009-12-16 09:47:00 How could Microsoft fix a problem caused by other people's drivers? Agent_24 (57)
840148 2009-12-16 22:50:00 Windows 7 x86 will see 4Gb and even report it, however addressing limitation of 32bit will NOT use the full 4Gb

we did this to stop wasting peoples time and money, calling up support when they had purchased 4GB of RAM in their machine, but Windows x86 was reporting 3.1/3.2/3.3GB depending on chipset/video card etc and they wanted to know why

If you've got 4GB in Windows 7, Win7 reports 4GB, even though all of the 4GB isn't usable because of those 32 bit architecture limitations

Thanks
Nathan
nmercer (3899)
840149 2009-12-17 00:51:00 www.microsoft.com
PAE, Physical Address Extension.
:)
Trev (427)
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