When is 4Gb not 4Gb??

[CHR1S]

So why is my laptop with 32bit Vista showing avaliable RAM as 4Gb in system properties yet a similar laptop with 32bit Vista is showing 3Gb in system properties and both show 3035mb (or 3Gb) in task manager when both have 4Gb??

Its too much for my brain today

Edit - I know 32bit can only address 3Gb before you all point that bit out lol!

[CPLTD]

So why is my laptop with 32bit Vista showing avaliable RAM as 4Gb in system properties yet a similar laptop with 32bit Vista is showing 3Gb in system properties and both show 3035mb (or 3Gb) in task manager when both have 4Gb??

Its too much for my brain today

Edit - I know 32bit can only address 3Gb before you all point that bit out lol!

is the display adapter taking some system memory bud

[Psymon]

Any of them have seperage graphics / sound cards?

The amount of RAM on these cards can usually be subtracted from the total that can be addressed as it needs to be mapped.

Si

[lew_bob]

You're first laptop is acutally a 64bit version of vista??

[Psymon]

Or Physical Address Extension is not enabled on one of the laptops.

BCDEdit /set

Si

[tmcd35]

Any of them have seperage graphics / sound cards?

The amount of RAM on these cards can usually be subtracted from the total that can be addressed as it needs to be mapped.

Si

Pretty much sums it up. Most devices (of not all?) plugged into the PCI bus and most Hard Drives and CD-Rom drives, etc all use DMA (Direct Memory Access) to control them. This means they all need to be assigned memory locations in the addressable range. So memory addresses for these devices are subtracted from your 4Gb limit and whatever is left you can use as RAM - typically between 3Gb and 3.5Gb.

[Michael]

I thought only Vista SP1 or later properly displayed 4GB, but whether it'll use that much in a 32bit environment is doubtful.

[StewartKnight]

Vista SP1 'knows' that you have 4GB, but can't address it all, as it see's the video ram first.

The maximum a 32bit o/s can see is 4gb of RAM, so if you're using a 32bit o/s and have 4gb of ram, you've just wasted 1gb of it as the os can't address that high!

[CHR1S]

Yeh, but why does one show 3gb and the other 4gb in system properties? Do the OEMs "adjust" it for show or can the GFX etc realy lose 1Gb?

[Michael]

I'm pretty sure it is to do with Windows and what Service Pack you have installed. If you haven't already, have you applied Vista SP2? I didn't think you could use 1GB as shared video memory. I've not seen it go that high in BIOS options. Typically 256MB is the limit.

[BandyQuill]

if you have vista SP2 it should show 4gb, however it will still only use 3.'something'

[CHR1S]

if you have vista SP2 it should show 4gb, however it will still only use 3.'something'

Its probably that, just couldnt get my head round it at all lol!! Just assumed it was naughty OEMs trying to fool the end user into thinking their 4Gb laptops used all of it under 32bit OS'.

[BandyQuill]

yeahhh its just Microsoft fleecing the user into thinking it has 4gb XD

[DMcCoy]

Physical RAM installed in the RAM slots is not the same as the amount left that is addressable by windows. The reason is shows two values is one is a report on physical amount installed and the other is the amount available to windows.

GPU, Sound and motherboard will all take memory from you 4GB maxim address space. It's a 32 bit problem more than a windows one.

[CHR1S]

Physical RAM installed in the RAM slots is not the same as the amount left that is addressable by windows. The reason is shows two values is one is a report on physical amount installed and the other is the amount available to windows.

GPU, Sound and motherboard will all take memory from you 4GB maxim address space. It's a 32 bit problem more than a windows one.

But 2 laptops with the same amount of RAM and same OS reported different total ram in system properties and same amount in Task manager, thats whats thrown me!