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Aztec
31-07-2007, 10:11
hi i have 4gb ram installed on vista x64 but only 2800mb is shown but in the bios all is shown any ideas?

Chenks
31-07-2007, 10:15
any of it being used for shared gpu memory ?

Aztec
31-07-2007, 10:15
hi, i do have a gx2 it may be but would it be that much?

Bootup05
31-07-2007, 10:47
What mobo do you have and is memory remapping enabled or disabled?

Tom
31-07-2007, 11:39
Get memtest running - that's 1.2GB that's missing, which isn't right.

Either that or, read your manual and find out if you're missing a setting. Does it even support 4GB or memory?

Does the OS show 4GB of memory and use it? You should run something like Prime95 on a memory test to check.

Aztec
01-08-2007, 09:30
hi, my 4gb ram is shown perfectly in x64 XP, its just vista ive got problems with, beginning to think vista is more trouble than its worth.

Tom
01-08-2007, 12:27
hi, my 4gb ram is shown perfectly in x64 XP, its just vista ive got problems with, beginning to think vista is more trouble than its worth.
So, did you look at any of the ideas I brought forward? :confused:

Aztec
01-08-2007, 21:10
i think the gx2 is using 498mb shared memory per core so thats nearly a gig of ram,??? is there any way i can change that as you know of?

Fat Jez
01-08-2007, 22:12
i think the gx2 is using 498mb shared memory per core so thats nearly a gig of ram,???


Not in the 64bit version it won't. Are you sure you aren't running the 32 bit version?

Cheers,
Stephen

Aztec
02-08-2007, 02:44
no m8 am running the 64 bit version, i think ive found the problem, was having a prob with sli on my gx2 not running any faster when enabled and its all down to my psu, it must be running at its peak because when i unplug the cdrom and a hard drive all the memorys showing, also vista will not shutdown when everythings connected, i replied to another thread in here yesterday about buzzing psus, well mines just started indicating an absolute peak load/and or a fault with it, in my case its overloaded, those gx2's suck power like hell, with my older ati x1900gt wasnt having the problem,well i dont suppose i would as its only a single gfx card, im now looking for a decent 650w or 700w psu, any recommendations? think ill go for the 700w actually as i may add a couple more hard drives to my system, thanks for the reply anyway, cheers.

Tom
02-08-2007, 21:02
i think the gx2 is using 498mb shared memory per core so thats nearly a gig of ram,??? is there any way i can change that as you know of?
You don't pay ~£550 (when new) for a card that uses a whole GIGABYTE of your system memory!! :eek:

It has its own, extremely fast, GDDR3 memory on-board ;)

Retroanaconda
02-08-2007, 22:12
It uses a gigabyte's worth of memory addresses though, and in a 32-bit system that would be a problem :P

Tom
03-08-2007, 12:59
It uses a gigabyte's worth of memory addresses though, and in a 32-bit system that would be a problem :P
.. What?! No, no it wouldn't be a problem.

You have a completely separate memory controller, and processor for the memory on-board a graphics card. It's in no-way shared with the system memory!

Fat Jez
03-08-2007, 13:02
.. What?! No, no it wouldn't be a problem.

You have a completely separate memory controller, and processor for the memory on-board a graphics card. It's in no-way shared with the system memory!

Not exactly. The graphics cards, and indeed all the other peripherals, map into the addressable memory space, which is why you only get about 3.2GB of usable RAM on a 4 gig, 32-bit system.

Cheers,
Stephen

Tom
03-08-2007, 13:19
Not exactly. The graphics cards, and indeed all the other peripherals, map into the addressable memory space, which is why you only get about 3.2GB of usable RAM on a 4 gig, 32-bit system.
This sounds as bizarre as it is stupid - I can understand why the CPU may need to address video memory (it's obvious) but why it would be on the same register as the system memory, is baffling.

The numbers just don't add-up either - 800MB for a 256, 512 or 1024MB of video memory?

Fat Jez
03-08-2007, 13:26
This sounds as bizarre as it is stupid - I can understand why the CPU may need to address video memory (it's obvious) but why it would be on the same register as the system memory, is baffling.

The numbers just don't add-up either - 800MB for a 256, 512 or 1024MB of video memory?

It's not just the graphics card that needs addressable memory, all the peripheral devices do. The CPU has a 32-bit address bus (assuming we are talking 32-bit OS here - obviously a 64-bit CPU can address more but is limited by the software), so can address 2^32 locations, or 4GB of locations. The graphics cards use some of that, but all the other devices in there (PCI cards, PCI-E cards, ports, etc) will also use space. In the case of the graphics card, I don't think it's a one to one mapping of the amount of memory on the card to how much addressable memory space it needs on the address bus.

Cheers,
Stephen

jesush++
03-08-2007, 13:42
Fat Jez is correct. All devices on the system that have their own memory need to be addressable. In a 32 bit system, this means that the maximum number of memory addresses runs at 4gb.

Tom
03-08-2007, 14:38
It's not just the graphics card that needs addressable memory, all the peripheral devices do. The CPU has a 32-bit address bus (assuming we are talking 32-bit OS here - obviously a 64-bit CPU can address more but is limited by the software), so can address 2^32 locations, or 4GB of locations. The graphics cards use some of that, but all the other devices in there (PCI cards, PCI-E cards, ports, etc) will also use space. In the case of the graphics card, I don't think it's a one to one mapping of the amount of memory on the card to how much addressable memory space it needs on the address bus.

Fat Jez is correct. All devices on the system that have their own memory need to be addressable. In a 32 bit system, this means that the maximum number of memory addresses runs at 4gb.
Well, according to this White Paper (http://www.polywell.com/us/support/faq/4GB_Rev1.pdf) (caution: PDF link) from Intel, you are both indeed correct. So I do apologise to all.

However: Going back to my original post about the graphics card not using shared memory - that's still very much true. Though I couldn't tell you why Aztec's motherboard BIOS, which supports a 64bit CPU is seemingly limited to 32bit registers (and seemingly doesn't take advantage of PAE?)

jesush++
03-08-2007, 17:14
He has put it down to not enough power getting through to all the devices. Its possible that some of his RAM wasnt showing up.

Retroanaconda
03-08-2007, 22:42
Ah yes, I see where I missed a part of it. The graphics memory would be dealt with on a seperate system entirely, so it doesn't use up the main system's memory addresses. The card itself, and all the other components of the system (ports/controllers etc) do though.

I got confused :)

Aztec
04-08-2007, 15:36
hi, the graphicscard (gx2) in the display driver on x64 vista is showing 464mb shared x2 for both cores, if i go into msconfig and tweak the memory settings all 4096mb ram is shown and the shared is then pointed towards virtual memory which is slower.

my motherboard is a p5nd2-sli

sorted the power struggle am now using 2 psu's