Thinkpads Forum

2 x 2GB RAM sticks installed,

BIOS shows 4GB, but when in Windows, it shows "3070 MB"



Anybody has spare a T61p motherboard?

3GB installed, show same result [3070 MB]

Vista Home 64bit? Or Biz?

64bit shouldn't have any issues with > 2 GB ram. XP 32bit has an artificial limitation at 3gb due to badly behaved 3rd party drivers, and I'd imagine they're carrying that to vista 32bit, but if you're running x64 that's definitely not right.

Did you install x64 yourself, or are you just using the preload? Vista preload on thinkpads is always 32bit.

It is 64bit Ultimate

You can only see 3GB because the upper parts of the memory address space for the current Intel mobile chipsets is reserved for addressing devices (like the graphics card, ect.). It will not matter what OS you run, it is a hardware limitation of all Intel based laptops.

There is no way to fix this. The upcomming santa rosa chipset will be able to see 4GB+.

Dimitri, thanks again for experimenting with your 2GB sticks. This is very helpful because the issue of whether the 64-bit versions of Vista can use all 4GB of RAM on these machines has been raised numerous times on this forum. We can now stop speculating or arguing.

so if i understand this correctly, even though my laptop can take 2 2gb chips totalling 4gb the system can only see and use 3gb?

gt5l wrote:so if i understand this correctly, even though my laptop can take 2 2gb chips totalling 4gb the system can only see and use 3gb?

Correct, that's due to intel's chipset limitation.

This topic has been discussed many many times , please see:

http://forum.thinkpads.com/viewtopic.ph ... ht=#271409

This information is also on the T60 datasheet; see e.g. http://www-306.ibm.com/common/ssi/OIX.w ... ersion=yes

- where it is expressed like this: "Important information about memory: On the T60 and T60p systems, even though it is possible to physically install 4 GB of memory, the actual amount of memory addressable by an operating system will be limited to 3 GB. This limitation comes from the current 32-bit PC architecture."

Johan

Johan wrote:This information is also on the T60 datasheet; see e.g. http://www-306.ibm.com/common/ssi/OIX.w ... ersion=yes

- where it is expressed like this: "Important information about memory: On the T60 and T60p systems, even though it is possible to physically install 4 GB of memory, the actual amount of memory addressable by an operating system will be limited to 3 GB. This limitation comes from the current 32-bit PC architecture."

Johan

That is why I used 64bit OS....

Still same , not mentioned

Dimitri_P wrote:That is why I used 64bit OS....

Your OS is 64-bit, your CPU is 64-bit... however the reserved memory locations imposed by the chipset are still in that space between 3.25 GB and 4.00 GB (roughly). If it were possible to have 4GB SO-DIMMs, I wonder if you would then be able to see memory between 4 GB and 8 GB with the current chipsets???

There's a great series of articles about this and the Windows "/3GB" switch here:

http://blogs.msdn.com/oldnewthing/archi ... 18527.aspx

taob wrote:

Dimitri_P wrote:That is why I used 64bit OS....

Your OS is 64-bit, your CPU is 64-bit... however the reserved memory locations imposed by the chipset are still in that space between 3.25 GB and 4.00 GB (roughly). If it were possible to have 4GB SO-DIMMs, I wonder if you would then be able to see memory between 4 GB and 8 GB with the current chipsets???

If for some reason you could get 4GB DIMMs and they could be installed in the current laptops, you still would not be able to see anything above 3GB. It has to do with the way addresses are decoded by the intel mobile chipset. The intel mobile chipset only uses a 32bit address space (which is 4GB), the upper part of which is reserved.