32bit OS

[ConTRo13R]

The maximum ram for a 32bit OS is 3.5GB (yea?), so if i had two gfx cards with 1gb of vram each then will only 1.5gb of normal ram be allocated?

Or will .5gb of vram be unusable

 

[ConTRo13R]

Hi ConTRo13R, the maximum amount of address space a 32-bit system has access to is 4GB and within this both your physical memory plus other critical functions that also need to map there memory resources into this space such as System BIOS, configuration for PCI/PCI-Express and any memory mapped I/O devices such as your graphics card. These functions take priority over your physical memory which means they are all mapped first so if for example these functions take up say 1.5GB, it means that the address space is then cut down to 2.5GB which will then result in the system only being able to address 2.5GB of physical memory.

One of the main functions that result in this inaccessible space is due to your graphics card. The amount of VRAM that a graphics card has access too; a large portion of this is mapped into this address space.

Thank you very much Fire Wizard, that explains a few thing iv been trying to get my head around.

Thank you once again

 

[ConTRo13R]

Ok, here's a question. Say you had 3 1GB graphics cards and something else that required a but of memory mapped I/O, would the BIOS/OS reserve any main system RAM? Would the system boot?

im guessing if that 'something else' took up .5gb the you would ahve another .5 to boot with.

If it took up 1gig then no it wouldnt, as the os cannot allocate any more memory, though you would get past the bios post

Or is that wrong?

 

[ConTRo13R]

iv edited my previous post after reading it again

 

[ConTRo13R]

Or would the OS change the allocation priority of devices so there would always be some system RAM left? So maybe reduce the amount of VRAM allocated?

I was thinking this but wasnt sure wheter it would make it past bios post, but it would as memory mapping is done by the OS.

In answer though id say yes it would deduct the minimun amount it would need to boot into the os from the vram

 

[ConTRo13R]

Any basis for this answer or just a guess?

half guess, but also seems half logical too.

this has turned very interesting, from just a quick query

 

[ConTRo13R]

how about two 295GTX's that pretty much rounds to for gigs then add another 2gb of the physical ram not to mention everything else that needs mapping all on a 32bit system, theres a set up to test

 

[ConTRo13R]

At Fire Wizard, as graphics cards are essentially there own plug in system then surely the OS wouldn't care about what size memory so this wont affect the amount of physical memory?