Quick question about 32-bit system ram limit.

[CreasianDevaili]

I am thinking of getting the 4870x2 2gb. I run 32-bit xp. I have 2 gigs of ram. If i get the card i should still have my gigs of system ram visible correct? I have no additional pci cards or anything of the like. However i am unsure what else will take up the ram limit.

I know some have 3.7gb of system ram if they only use 256mb GPU, but others have alittle less system ram in the same settings. So i know there are other factors.

If someone dosent mind, can someone help me figure this out?

No extra pci cards, 1 HDD 16mb cache. 2gigs of system ram, and plan to get the 2gb vram 4870x2. Would like to stay with xp 32bit. I dont want to lose any of my system ram if i can help it.

Thanks to anyone who can help.

 

[Lorne]

The GFX card will not affect your system memory.
The only time you would have system memory and GFX memory issues is if the GFX was onboard then it would share, Otherwise you have nothign to worry about with an addon card.

 

[CreasianDevaili]

Originally posted by: Lorne
The GFX card will not affect your system memory.
The only time you would have system memory and GFX memory issues is if the GFX was onboard then it would share, Otherwise you have nothign to worry about with an addon card.

I mean that 32-bit os can only account for 4gb of ram total. So if you have 4gb of system ram, and have a gpu with 512mb of ram that you will only see 3.5gb of system ram in windows. However i thought there was other things that take away from the memory address limitation on 32-bit OS. I wanted to verify. Cause with how my system is the 2gb of vram should allow my 2gb of system memory to remain untouched. Like if i added the 4970x2 2gb to xp 32-bit and i had 3 gigs of ram.. that i would lose 1gig because windows can only account for 4gb total across the system.

 

[MagnusTheBrewer]

Originally posted by: CreasianDevaili

Originally posted by: Lorne
The GFX card will not affect your system memory.
The only time you would have system memory and GFX memory issues is if the GFX was onboard then it would share, Otherwise you have nothign to worry about with an addon card.

I mean that 32-bit os can only account for 4gb of ram total. So if you have 4gb of system ram, and have a gpu with 512mb of ram that you will only see 3.5gb of system ram in windows. However i thought there was other things that take away from the memory address limitation on 32-bit OS. I wanted to verify. Cause with how my system is the 2gb of vram should allow my 2gb of system memory to remain untouched. Like if i added the 4970x2 2gb to xp 32-bit and i had 3 gigs of ram.. that i would lose 1gig because windows can only account for 4gb total across the system.

I think you're misunderstanding how the OS ram limitation for 32 bit works. The ram on your GPU is NOT part of the system ram and would be included only if your board used shared ram for video as Lorne said. The OS does not need to address each bit of the GPU ram. The drivers for the video card(s) are what affects the 4 gig limit on 32 bit OS's.

 

[Rebel44]

When I tried SLI 2x 8800GT 1GB with 32bit os (XP SP2) system had only 1,6GB RAM available (4GB installed).

 

[0roo0roo]

http://www.dansdata.com/askdan00015.htm
chunks are taken, not just by video cards.

 

[palladium]

Just wanna be sure if I get this right:

According to the article linked by OrooOroo ( and my understanding), the OP will have likely to have slightly under 2 GB of addressable RAM ( due to MMIO). This would have been the case whether he uses a 4870x2 with 2GB RAM, or a 3650 with 256MB of RAM. If he goes with the 4870x2, installing another 2GB of RAM wouldn't help much if at all, because the OS has to address that 2GB of video memory. I am assuming that no system RAM is allocated for video memory.

Did I get this right...?

 

[tcsenter]

Originally posted by: CreasianDevaili
If someone dosent mind, can someone help me figure this out? No extra pci cards, 1 HDD 16mb cache. 2gigs of system ram, and plan to get the 2gb vram 4870x2. Would like to stay with xp 32bit. I dont want to lose any of my system ram if i can help it.

There is no way to know exactly how much address space this card will request during PCI configuration and how much the chipset-specific BIOS will reserve to it, without plugging it in and finding out. Or finding someone else who has the same setup.

 

[Crusty]

Lot's of misinformation here.
First off I recommend reading and understanding the following wikipedia articles:

http://en.wikipedia.org/wiki/Virtual_memory
http://en.wikipedia.org/wiki/Physical_Address_Extension

As well as http://www.microsoft.com/whdc/...server/PAE/PAEmem.mspx

All 32-bit OS's are quite different in terms of memory. In order for a 32-bit OS to see more then 4GB of physical RAM the CPU of the system needs to support PAE. If the CPU supports PAE then the OS has the ability to addresses up to 64GB of memory. Note that this does not mean that all 32-bit OS's will support that amount of RAM per the wikipedia information. The reason MS does not allow more then 4GB of addressable space is due to drivers being incompatible with PAE. This is mostly an issue of the past since most modern drivers for current hardware will support PAE properly, but given that MS has moved to 64-bit OS's already I doubt it's worth their money to update XP 32-bit to support more then 4GB of addressable space.

I wont go into details of an OS, but the gist is that MS uses MMIO for hardware devices so any address spaces that the hardware needs gets taken out of the address pool. XP 32-bit also only supports up to 2GB of Address Space per Process, but that's hardly relevant. In the end, it doesn't matter if you have 4GB or 64GB of ram, Windows XP 32-bit will only allow you to access [4GB - (amount of address space your hardware requires)] of physical RAM due to MMIO, with each process only allocating up to 2GB of Virtual Space which is made up of Physical RAM + Swap Space.

What is hard for people to understand is that what the hardware can use is different from what the OS can use, which is different from what each process in the OS can use, on top of that all of this varies from OS to OS.

 

[Nothinman]

with each process only allocating up to 2GB of Virtual Space which is made up of Physical RAM + Swap Space.

Actually virtual memory is just made up of physical memory. When something gets paged out to the pagefile or is backed by a memory mapped file it still has to be paged into physical memory to be used.

 

[CreasianDevaili]

This is why I get confused. I wont nod my head and say i understand something if i dont. Dont learn what you need to that way.

I am confused on it, so naturally i explained myself in a way that just screamed newbie. However that is truth on this particular aspect.

I, as i stated have 2gb. I have been researching to find out how much of the address space is being used by my devices right now. I should then be able to roughly calculate how much the 2048mb on the 4870x2 should encompass as well, and see how much of my physical memory windows will show, thus, use when i game etc.

I could live with 1.9gb of system memory after everything else takes it's peice of the pie. I dont want to end up with 1.7gb or less. That is my issue.

I have seen some people with a 768mb card and 4gb installed on 32-bit os and show almost, aside from the 768mb of vram being addressed, 3.17gb of system ram. That shows 158mb of the memory address being used by other devices.

That what i would love to learn and find out for myself. I know pci cards can take up alittle of the address, as can HDD if i am right. That was why i listed all of my components. I run a very clean system and aside from insane memory leaks on my mmorpgs I have never used up all of my system memory. Even then it takes many hours.

So i know what I NEED to have still available for system ram. I was wondering if anyone knew how to calculate the other devices, using device manager and looking up the memory, so i could try to estimate within reason.

As Tcsenter said wont be able to find out unless someone else with the same setup just about with a 2gb vram card gives me their numbers after its all said and done.

I do appreciate all of the replies. Again if i am not trying to be stubborn here. It wont work but it was a worthy shot in the dark.

 

[Nothinman]

Is there a reason that you're not considering a 64-bit OS and saving yourself the hassle?

 

[tcsenter]

Originally posted by: CreasianDevaili
I have seen some people with a 768mb card and 4gb installed on 32-bit os and show almost, aside from the 768mb of vram being addressed, 3.17gb of system ram. That shows 158mb of the memory address being used by other devices.

Graphics RAM is not necessarily going to reduce address space available for system RAM in a 1:1 manner. Any current full-featured chipset is going to grab at least 600MB of address space straight away before you install a graphics card. Some of this reserved address space can be inclusive of the devices that might get installed.

For example, the PCI bus will always grab 256MB per the PCI spec, whether or not there are any PCI cards. This 256MB is an available resource for all PCI devices enumerated on that bus, minus some amount that is locked for exclusive system use. Arbitrarily assuming that exclusive amount is 32MB for sake of discussion, that should leave 224MB available to PCI devices. If you install a PCI card that requires 128MB address space, it should be able to 'fit' within the 224MB that is already reserved for PCI use and have no additional impact on memory hole overlap.

That is an oversimplified treatment to the point of technical error, but not conceptually wrong. As long as the resource requirements of the cards that you install do not singularly or combined require more than what is already reserved by default, you're not going to grow the memory hole in a 1:1 fashion.

Additionally, there can be convoluted things going on like IOMMU device windows similar to the GART for AGP, blurring the distinction between I/O and memory addressing or between virtual and physical mapping. Don't ask. I get the general idea of what it does, I just don't understand how. Maybe Nothinman can expound a little more on that.