To be clear, you NEED 64-bit to see more than 3GB of RAM!

[underclocker]

Informational Post

I've read many of the threads over the years about XP, Vista, and now Win7's, memory limitations. However, it was not entirely clear to me that current ThinkPads with Windows 7 32-bit DO NOT support memory over 3GB.

After aquiring a couple of T500's and working on two T410s machines, all with Vista or Windows 7 32-bit, it is painfully clear that 3GB is the maximum that can be addressed by the 32-bit versions of either Vista or Windows 7.

You may have read that they "support" 4GB, even XP is claimed to "support" 4GB, but it simply does not on any ThinkPad.

In fact, unless you fiddle with BIOS settings, a switchable graphics model T500 will only show 2.5GB as usable! An 8 year old T30 supports 2GB of RAM!

Lenovo should disclose, in a large font, issues with configuring and buying machines with 32-bit OS's and over 3GB of RAM. You can not use the memory you purchased.

So, you not only need a machine with a chipset that supports addressing memory above 3GB and a CPU that supports a 64-bit OS (most machines above T60/R60/X60/Z61 vintage), but you also need a 64-bit OS version, if you plan to run a Microsoft desktop OS and use more than 3GB of RAM.

Bottom line, for any machine that supports more than 3GB of RAM, I'd recommend going with the 64-bit version of Vista or Windows 7 even if you have compatiblity issues with hardware or software. Otherwise, you'll never be able to use more than 3GB of RAM without an OS upgrade (most likely never, anyway, since technically, Microsoft can fix the issue w/32-bit OS versions - but that is another story).

[craigmontHunter]

you right - they should. They used to s mention that you need a 64-bit os to access all memory over 3gb. When you select 4 or more gb (in canada at least), it said in bright red letters above the selection "You need a 64-bit Operating System to access all the memory over 4gb". I wonder why they took it away?

[casperkid]

Microsoft claims that it is not their fault and is instead a limitation of the 32 bit architecture. At first glance this seems correct. 32 bit processor using 32 bit registers should be only able to address up to 4 GB of RAM (232 = 4G). However, this is not actually true. The main reason being a feature called Physical Address Extension (PAE).

PAE makes it possible to address more than 4 GB of memory using 32 bit registers, since the registers aren’t used to store the physical address. Instead, the registers store linear addresses, which are mapped to physical addresses using the page table. This feature has been available since the days of Intel Pentium Pro. In x86 processors additional address lines are provided so that up to 64 GB can be addressed when using the PAE mode. If you want to learn more about Windows memory addressing, go through Geoff Chappell’s notes.

Windows Vista and 7 have two kernels – one which doesn’t use PAE and one which does. They are NTOSKRNL.EXE and NTKRNLPA.EXE respectively. Both of them reside within the Windows/System32 directory. Can you guess which one you are using? If you have a modern machine, then chances are that Data Execution Prevention (DEP) is enabled in your system and in that case you are already using the kernel with PAE enabled.

How to Enable More Than 4 GB Memory

Before getting started, keep in mind that this patch involves modifying the kernel. Do no proceed unless you are confident. Most security products will identify these patches as malicious since they modify the Windows kernel.

Download the appropriate patch for your system (links at the end of this post). I haven’t tried the Windows Vista patch, but I can confirm that the Windows 7 patch works. The Windows 7 patch is in Russian language. To begin patching click on the big button (refer to screenshot). After this a command prompt window should appear. Press Y.

On restarting the system, you should see two entries in the Windows Boot Menu – one being the older configuration and the other being the one with support for more than 4 GB RAM. If you don’t want to be prompted every time, press Win + R, type msconfig and hit Enter. Under the Boot tab, reduce the timeout value (to something like 3 sec). If you wish, you can simply get rid of the older configuration by deleting it. But I wouldn’t recommend this. If you get a water mark (Test Mode) on your desktop after restarting, type mcbuilder.exe in the Start Menu and press Enter.

Simply download this and apply patch: http://www.mediafire.com/?ajyngdyz9xj

[w0qj]

Anyone able to confirm casperkid's program works and will not corrupt RAM memory and/or your data?
(And trust this program is not a Trojan program!)

[ashleys]

Microsoft claims that it is not their fault and is instead a limitation of the 32 bit architecture

That was never strictly true and they dealt with 32-bit address limitation and PAE differently depending on whether it was a server OS or a client OS.
See the following good article by Mark Russinovich on the reasons behind the decisions for various OS's and what does happen when using RAM above/at 4GB.
http://blogs.technet.com/b/markrussinov ... 92070.aspx