Vista 32bit - RAM

[kirennia]

Okay okay, I know this is an age old topic but it's still interesting me. Heres the deal.

My housemate and I now both have 4gb ram installed (he has 4x1gb sticks, I have 2x2gb sticks) and both have the same copy of vista installed. In fact, we used the same CD but don't worry it's legal; the university for our faculty gives you the .iso CD and you install it with a key they give you, hence the same CD.

His dxdiag says he has 3.02gb installed.
My dxdiag says I have 3.326gb installed.

So why the difference? I understand vista caps it and knew this before I bought it, I just wanted to future proof myself a little ready for windows 7 when it hopefully accepts more then this amount of RAM. Is very interesting... the only difference I can really think of is that he's using an AMD chipset and mines intel. Or that I'm on quad and he's on a faster duel core? Graphics cards/motherboards surely wouldn't make any difference as they can both support over 4gb RAM anyway.

So for other vista 32bit users here, could you see how much your dxdiag registers (if you have 4+gb installed that is)? I'm interested.

 

[Vae]

Does one of you have integrated graphics by any chance? If so it could possibly be to do with memory being allocated to that. Just a thought.

 

[Cadelin]

Isn't it the total amount of memory that can be addressed? So it counts both normal RAM and video RAM. So it looks like he has 0.324 GB of extra video RAM.

 

[Deebs]

Also you lose some memory from the 4gig for the PCI address space, unless they are identicial PC's then you will have a different value depending on bios settings, cards especially video. As vae mentioned if it is integrated they normally steal some of the mainboard RAM as video ram.

 

[Bob007]

Windows reserves ram for sub systems. As Deebs says, PCI bus will take some for address as will graphics cards, differing models/graphics card ram sizes will result in differing amounts of memory from the amounts above the "3.X" gig limit of 32 bit OS's. Gcards will be the biggest users taking anything from 1/3 to an amount equal to what they have on the card.

32 bit or 4,294,967,295* (if you start at 1 and double 32 times to get your "32 bits") = 4 gig minus sub system addressing = memory shown by windows that is useable. hence the difference.

Funky stuff starts when you have same systems with same OS and showing differing amounts.

*Wasn't working that out

 

[kirennia]

For the graphics cards I'm currently running a 1gb 4870 whereas he's on the 1gb 3870x2. Maybe it's just dxdiag presuming I'm not going to run it at full capacity with this ATI overdrive facility running.

Cheers for the info though guys

 

[Embattle]

Only 512MB of his 3870x2 1GB card will be mapped, which is why he has more ram than you. I've got a 4870X2 2GB and basically like your friends 3870X2 only half of this memory is mapped since on the card the 1GB of image data is actually mirrored to the other 1GB.