4GB RAM on T400

I have 4GB of DDR3 RAM installed on my T400. Before I switched over to Vista Business 32, I ran XP Professional. With 4GB of RAM installed, XP showed 2.99 GB of RAM under the Task Manager. I expected XP to show something just over 3GB. I upgraded to Windows Vista Business 32-bit yesterday, and the machine seems to run very well in Vista; I'm impressed. When I checked the total RAM in the Task Manager, however, it only shows 2.5GB. When I go to the "System Properties" of Vista, it shows 4.00 GB of RAM.

I figured that Vista's Task Manager would show something in the 3.0 - 3.3 GB range. Is there something I need to do to free up some of my RAM?

Keep in mind that this is on a new system with all of the "bloated" software.

 

You are likely running 32-bit versions of XP and Vista. Keep in mind that video memory is also counted towards the maximum usable RAM, which theoretically is ~3.5GB. To use all 4GB, you'll have to use Vista 64-bit.

 

Yep, you're already using Vista. No reason at all not to install Vista X64.

 

I am not expecting to be able to use all 4GB since I have the 32-bit version of Vista Business. I am just curious as to why I am not even using atleast 3GB.

 

Because every bit of hardware uses address space, the memory is last in line. You're using 1.5GB of space for all of your other hardware. As for the XP/Vista discrepancy, don't really know.

 

No reason to go to 64-bits? Given that another OS is just around the corner maybe your right if he rembers to order 64 bits with Windows 7.
-Renee

 

From what I've read, Microsoft did some tweaking so that 4GB of RAM does show up in System Properties (to prevent consumers from being confused) but the laptop deceptively only uses ~3GB of it.

 

well if you really want to try it out why not?
see if there is a performance difference..

but i agree with the other guys above.

 

Yep, I'm using Vista Home Basic (it's not so bad) and have 4GB installed. It shows 4.00GB in System Properties. But other tools show that only 3.45GB is being used/addressed. It would be less than that (as low as 3GB) if I had dedicated graphics.

I had planned to upgrade to Vista Home Premium 64 or Business 64, but I'm content with Basic and 3.45GB for now...

 

I know that. But for him XP was using ~3GB, Vista is using ~2.5GB. That's the discrepancy I am talking about, for which I really have no explanation.

 

A regular 32-bit OS will show about 3.1-3.2 on a ThinkPad. However, the rest of your devices use some of that memory for address space so you will see less than that. Plus you have switchable graphics, which will take another 500MB+ of memory because it reserves memory for both Intel and ATI graphics. It makes sense you only see 2.5GB.

I would go 64-bit for the full 4GB memory.

 

I would guess it relates to the switchable graphics. I have a T500 with 4GB of RAM and no switchable graphics and IIRC, Vista used about 3.5 GB of RAM.

But I don't recall hearing of anyone who only saw 2.5 GB after a 4GB upgrade, so I suspect that there is some bios setting or driver issue that is causing this. I recall reading that some setting had to be changed in the bios to switch between graphics adapters in XP that was not needed with Vista. Is that set the wrong way for Vista?

-hank

 

whatever the OS, you can choose (via bios) just one or the other of the gpu's (discrete or integrated). if you want to be able to gpu-switch in vista, more ram needs to be set aside (hence ability to gpu-switch "on the fly", without resetting through the bios and rebooting ).

 

it is the switchable graphics that is eating your ram. it was posted a few months back. only 2.5gbs will show if you have 4gb installed. the way around is to go into the bios and choose for your operating system not to switch and then you will see 2.9gb or something. But you do lose the switchable graphics option.
everything is a tradeoff

 

Oh, awesome. Thanks for the info on that.