3gb ram read as 2.5? t400 vista

using a t400 with vista 32 home premium and should have 3gb of ram

task manager and cpu z read 2519 mb of ram
windows control panel says 3.0 gb of ram (but I think that's just inputted in before hand and not actually read in real time)
however cpu wizard reads 1 dimm of 2gb ram, and an empty slot

what's going on here? how do I check if my laptop was built correctly for sure?

thanks

 

open it up and see if there are 2 dimm

 

how do I open it up?

 

Its Vista 32 not reading more than 2.5GB.

 

ah... I thought the limit was 3gb, I guess people were just rounding up?

 

Integrated video card uses part of the system RAM for video display. Discrete Video card doesn't do that.

 

not entirely true. 32 bit OS can only address a certain amount of memory no matter where it comes from. Dedicated video cards take up addressed memory just the same as integrated memory. It just doesnt use your system ram like integrated cards do. 2.5GB is about right for 3GB installed Ram. Some systems/bios read it differently. With Vista SP2 most people got the piece of mind in seeing the actuall installed memory, but did not get any memory performance improvement.

 

not entirely true

my nVidia has 128MB on board memory but uses up to 512MB .. so the rest above 128MB are used from the system ram

in a 32bit system there are 4GB total addresses, so every computer component has to participate in the system. It's called memory mapping, eventhough it should be called address mapping, lol.

interesting case would be mine where I have 4GB RAM, which would occupy all addresses, or in other words my computer would consist only of RAM .. which would suck because I figured that I need monitor, keyboard, mouse, processor, modem, lan cards, video cards ... and others. So some of the upper addresses are marked as unusable for RAM so that there is space for the other devices.

to add some confusion I will add that it is possible to address more space indirectly, but that, as far as I know, doesn't apply to computers but does to microcontrollers ... so just disregard it as of now

 

to know how much ram you have, look in your BIOS

 

Simple: Use your eyes. Two minutes, four screws.

 

I realize that I could have worded that a little differently after I posted it, but Im tracking with what you are saying. A better example would be that my BFG 8800GTX's are both 768MB Ram, my system shows that I have 2.3 GB memory. Those do not use any system Ram but still takes up addressing of the 4GB total Ram I have installed.

I guess the moral of the story now is to get 64bit, things seem to work more now with 64bit than say a year ago.

 

there are more than four screws... and I believe I read that the t400's RAM is harder to access than previous models, so I don't want to unnecessarily tinker around with my hardware without knowing exactly what I'm doing...

 

Have you done this or are you guessing? I've done it. There are exactly four screws to remove the palmrest and access the memory slots. Very easy. One more screw and you can pop off the keyboard and check out antenna cable routings, where the wifi, modem, wwan, and other cards go, etc.

Check out the Hardware Maintenance Manual for details.

Does someone have a link to that service training video showing how to do this, I think that'd help assuage fears.

 

It doesn't appear to be up yet, but keep an eye out for it at:

Lenovo Service and Support Training

 

nope, never done it, I just vaguely recall reading something about that on these forums before (maybe it was the t500, or maybe it was all my imagination)

thanks for the link though, that's exactly what I was looking for! now to find a screwdriver small enough...