Memory 32-bit memory limitation confusion

Right, to start off I wasn't sure whether to put this in the hardware section or the software section, as it's a bit of both.

As you may or may not know, when you have a 32-bit operating system you are limited to 4Gb of total system memory inluding graphics card memory, so if you had 4Gb of RAM installed and a 512mb graphics card, you would only get to use 3.5Gb of your ram. Thats all simple enough, but I have a 4870 x2, which has 2Gb of memory in total, 1Gb for each GPU. Does that count as two out of my four available Gigabytes, or only one, as the contents of the two 1Gb sections is duplicated across the two cores, effectivly giving it only 1Gb of VRAM.

Thank you in advance for any help/suggestions

 

It's actualy more like 3.2gb you are limited too.
The vram is not included in this.

 

Erm, what? It has 2GB of vRAM.

Windows will preferentially allocate memory address space to the graphics card first and system memory second, so yes, in theory you will limited to 2GB of your regular old DDR2 (which won't be much of an issue for you if you only have 2GB anyway).

The bigger issue is why you are running a 32-bit OS in this day and age. If performance is a problem you might want to grab a copy of the Win 7 RC until it's released or you have enough funds to buy a copy.

 

no, what i meant was that although the card has 2Gb of vRAM in total, its just 2 copies of the same data for the two GPU's to acces independantly. So you can only store 1Gb of unique data in the vRAM

 

Yes but the two 1 GiB banks will still need individual addresses I would have thought.

Infact I would say they will as I doubt Windows would let you duplicate memory addresses as that would cause all kinds of problems.

It doesn't matter whats stored in them, each block of memory must have an address.

 

Uh, my understanding was that is operates in the same way as Crossfire, but in a single card rather than two connected by a bridge. So each GPU will have 1GB of memory allocated to it and each GPU renders alternate frames (or uses the checkerboard method, I'm not too sure), so there are two sets of data rendered by the two GPUs.

Of course I could be totally wrong, but that's how I've always assumed the x2 cards worked; it seems like storing two copies of the same set of data in the framebuffer would be an incredibly inefficient way of rendering a scene, so I doubt ATI would have engineered it that way.

 

Not sure if this helps, but there was a good article on Bit-Tech about this:

Clicky

 

will windows 7 be released in a 32bit variant....if so why?

 

Yes, as there will be 32 and 64bit versions on the same DVD. Also, the MSDN academic download site has discreet 32bit and 64bit versions for download.

Why? I have no idea.

 

probably for netbooks, Atom N270 don't have support intel-64 (or whatever they call it)

 

Thanks Wildthing, a very good read

Anyways, I've just got the win7 release candidate (64-bit of course) so problem solved, that is, until we start needing more than 16Tb of Ram

 

Just out of interest, if you go into device manager, and click on display adapters, then click resources, how many IRQ are displayed for your 4870X2?

 

http://i157.photobucket.com/albums/t54/buddharoxor/Win7PRO.jpg

Legit pre-release Win7 Pro.

 

and your point is?

 

I'm very pleased with it

(You have your product ID showing, not sure if thats important or not)

 

the 4870X2 is listed as two seperate display adapters (presumably because of the two GPU's), each of them is listed as having an IRQ of 16.

Sorry for the late reply, the menace known as school has started again

 

Isn't it 64 Exbibytes of RAM but it's windows that's limited to 16TiB?

EDIT: I think it's 16 EiB's but I just done it again with a calculator and it came out as 64 so I'm confused >.<

 

That tool bar for Win7 looks so confusing. Sorry but i haven`t used Vista or Win7. I've used Windows XP for many years now but plan on using Windows 7 in my new rig. Looks like i have a lot to learn on the OS side of things.

 

Well that's probably because you were putting the wrong numbers in.

It's 2^64.

 

Windows supports max. 2TB of RAM.

Check this out: http://blogs.technet.com/markrussinovich/archive/2008/07/21/3092070.aspx



Oh yes, that is 2TB of RAM in a computer.