Thinkpads Forum

I was told that running windows vista that the T60 can only use 3GB of ram. If this is true, why can it not use the full 4GB?

I'm not sure why, but that's how it is.

This is a limitation of Windows going back to the good ol' DOS days. Windows can't support anything more than 3GB. However, if you install Linux (Ubuntu, Fedora, OpenSuse or any other variant), all 4GB of RAM will be recognized.

Fedora runs really nicely on my T60. I might give OpenSuse a whirl to take advantage of some of Lenovo's utilities for Suse.

What about the new windows vista?

Surely the new games and programs will be needing more and more memory?

official answer from Microsoft:

32-bit versions of Windows Vista Home Basic, Home Premium, Business, Enterprise, and Ultimate: 4GB
32-bit Windows Vista Starter: 1GB
64-bit versions of Windows Vista Home Basic: 8GB
64-bit versions of Windows Vista Home Premium: 16GB
64-bit versions of Windows Vista Business, Enterprise, and Ultimate: 128GB

So I search around a little to find some real-world experiences for people with 4GB installed:



This guy had 3.2GB available.
People here had 2GB, 3.58GB, and 3GB available.
This guy had 2.5 GB.
And this guy had 2.8GB available.
This paper from HP helps explain it–the platform can theoretically support the full 4GB, but your hardware is going to allocate some of the address space (not the physical RAM) to the PCI bus, the video adapter memory address space, and other resources. 32-bit OSs need to use part of the full 4GB address space to address these resources, subtracting from the maximum memory you have available to the OS and applications:

The PCI memory addresses starting down from 4 GB are used for things like the BIOS, IO cards, networking, PCI hubs, bus bridges, PCI-Express, and video/graphics cards. The BIOS takes up about 512 KB starting from the very top address. Then each of the other items mentioned are allocated address ranges below the BIOS range. The largest block of addresses is allocated for today’s high performance graphics cards which need addresses for at least the amount of memory on the graphics card. The net result is that a high performance x86-based computer may allocate 512 MB to more than 1 GB for the PCI memory address range before any RAM (physical user memory) addresses are allocated.

So, if your video adapter has 512MB of RAM (like mine does), your maximum memory is going to at most be 3.5GB, because Vista has to use 512MB of that address space to address your video memory. It’ll actually be lower than the 3.5GB because there are other hardware resources that need address space, too. So, it never hurts to fill your computer with 4GB of RAM–you’ll definitely get the max, but you won’t be able to address it all. You probably won’t be able to address much more than 3GB, and you might not be able to address more than 2GB.
The paper also mentions something interesting about 64-bit computers. Basically, depending on the hardware, you might be limited to 4GB of RAM even if you install 64-bit Windows Vista:

Windows XP Professional x64 Edition uses 64-bit addressing enabling virtually the entire amount of installed RAM to be made available on computers that have large address infrastructures (where the entire system has more than 4 GB addressing capabilities via the processor, chipset, physical memory capacity, etc). The HP xw4300, xw6200, xw8200 and xw9300 Workstations have the required infrastructures and even the PCI memory address range is recovered by re-mapping it above the top of physical memory.

http://www.vistaclues.com/reader-questi ... ows-vista/

So the 64bit OS resolves the RAM problem, but now it's just the hardware needs to be made to be 100% useful with that much RAM it sounds like?

Very interesting.

It can use 4G of RAM *IF* you have a 64-bit CPU and a 64-bit OS. If you got stuck with one of the early Intel chips, you are stuck just like me. Win32 has issues letting you access all of that last gig. If you use win64 (whatever variant) all four gig should show up.

So if I got a new T60 it would be able to use all 4 gigs of memory?

Would this give me more video memory then as well?

cybyte, do you know how insanely expensive 2GB modules are?

I looked them up once, but I'm assuming that as computers can now use more ram, the prices will be dropping. But I would like a computer I can upgrade later in the future.

Seriously, I can't do ANYTHING to make this sucker use up all 2 GB I have. Vista might change that, though.

cybyte wrote:So if I got a new T60 it would be able to use all 4 gigs of memory?

Would this give me more video memory then as well?

No. Current ThinkPad chipsets are limited to 4 GB, from which space is taken for i/o and video memory. In practice, then, the ThinkPad available memory is limited to 3 GB regardless of the OS you run.

This will not change until Lenovo starts using the "Santa Rosa" (Centrino Pro) chipsets sometime this year.

hmm maybe I can hold out and wait till then. We shall see

Hey, "nobody will ever need more than 640K of RAM."
- William Gates III

Or was that 3GB?

LoL.

claudeo wrote:Hey, "nobody will ever need more than 640K of RAM."
- William Gates III

He said "640K should be enough for anyone", and that's certainly correct back in 1984.

Gates may have been wrong about that, but he recovered nicely. Ken Olsen, on the other hand, has spen the past 40 years telling people that's not what he meant.

There is no reason anyone would want a computer in their home.
- Ken Olsen President, Chairman and founder of Digital Equipment Corporation, 1977

Ed Gibbs

I believe a modest amount of memory in the 32-bit addresss space can be reclaimed by disabling unneeded option ROMs e.g. the boot-from-LAN support (Intel PXE).

Regardless of OS and address width, what's needed for >3 GB is memory remapping.
Both the chipset and the BIOS have to support this. There's several desktop mainboards that currently have problems with this (e.g. Asus P5B), even though their chipset supports it.