Windows 7: 3 Gigs Ram or 4?

sygnus21 · 29 Oct 2010

@ DeconFrost,

Have a look at this http://www.corsair.com/_appnotes/AN8...e_Analysis.pdf, page 2-3 does a good job of explaining MMIO (Memory Mapped Input/Otuput) and it's relation to video cards.

DeaconFrost · 29 Oct 2010

I'm not debating the validity of the claim...I'm just saying that's honestly the first I've ever heard of a link between max memory supported by the motherboard, and what an x64 OS can still use. I think maybe you guys are misunderstanding me. I'm not suggesting the info is wrong or that the links are wrong.

GeneO · 29 Oct 2010

Some references:

BIOS remapping and holes (holes being gaps in the physical memory you cannot access because devices are mapped to that address range):

Ask Dan: What's with the 3Gb memory barrier?

PCI hole - Wikipedia, the free encyclopedia

The reference pdf at the bottom of the wikpedia article is very clear and readable.

Solarstarshines · 29 Oct 2010

I remember me and geno kinda talked about the memeory remapping/ memory hole feature as well to pci latency Depending on the amount of ram you are allowed or using at the time the memory is remapped through the pci devices

Pci latency is how effective you want the cycles to be between devices settings from 32 to 248 on some you would think higher is better but not always

then you have crackle hissing noises period from to high of a latency settings are far as the memory goes even if the board supported 4 gigs of ram it is still going to remap it to a pci device anyway and you wont get that full 4

like was said before you can get a higher ram device but even though it has its own ram some of the installed will be ramped anyway

pretty much this is what im reading ? Right or wrong ?

GeneO · 29 Oct 2010

Deacon,

I had tried to simplify my explanation and misspoke when I said the amount avail = max memory your MB support - video ram. It is max address space your chipset supports - video ram. The two are not always the same.

The latest Intel X chipsets have 36 bit (64GB) of addressing so this is no longer a problem.

zzz2496 · 29 Oct 2010

Quote: Originally Posted by GeneO

Quote: Originally Posted by zzz2496

Hmm... This is very weird... If what GeneO wrote is true, then I should only have less than 3GB available to my OS (which is NOT the case). I know that the chipset (or the memory controller in particular) needs to have the ability to access all of those memory banks that it's connected to, but Wow... This topic is very interesting indeed.

If you read my system specs, I have 2 display adapters, a GTX285 1GB and 8800 512MB... Those two alone should reduce my 4GB installed RAM to 2.5GB available to the system... But currently, all 4GB RAM is usable, even back in WinXP 32bit, I have around 3GB RAM available (with 4x1GB sticks installed). This is still not counting all other devices that are installed on my PCI(e) bus. As for display adapter's local RAM, it's a whole different device, and it uses different access method, and is addressed differently. In case you're wondering by this fact, the simple question would be: can you access the graphic adapter's local cache as a "real" RAM and have CPU a complete control over it? As if it's an extension of main memory...? Hint: display adapters have firmware that governs it self, we can say that it's more like a BIOS for display adapters, thus you can't really access it's RAM directly, not with that firmware in the way.

But enough... What to remember is, before you put in more RAM to your computer, you should ALWAYS read what's the maximum RAM size supported by your motherboard's memory controller. This is the main requirement of how many memory banks the memory controller can access/control. Regarding memory mapping feature, this is perquisite with the chipset's ability to address it's RAM. If it supports more than 4GB, it will have memory mapping feature.
The next factor is the OS. To be able to use all of those RAM, we need an OS that have enough address space to use all of those RAM. http://www.sevenforums.com/general-d...omparison.html have all the info.

As for the OP, as stated by rich64, Darician, Zeplash, stormy13, and many others (and my self): Stick with 3GB if you're planning on using 32bit OS, upgrade to 4GB if you wish to use 64bit OS... As simple as that.

zzz2496

Edit: I'm not sure if I read the thread starter correctly... The OP have a physical display adapter card, which is the same as me. After that, I re-read GeneO's post once more. If I read it correctly, maybe GeneO means display adapter that's embedded on the motherboard's chipset (an onboard display adapter). If this is the case, then we are not talking about the same thing. Onboard display adapter's local cache uses main RAM, this is true, but the OP's are using a dedicated display adapter card, which doesn't share it's local cache with main RAM...

Your motherboard supports up to 32 GB of RAM hence it supports up to 32 GB of address space and you are running x64 and I expect that you have memory remapping (or hole remapping) set in your BIOS, or your BIOS does this automatically. So you should see all of your memory. Your video graphics cards are probably mapped to the unused upper addresses of the 32GB of address space.

You will only see less usable than the amount of RAM you have installed if your installed RAM > MAX RAM supported by board minus your video RAM. In your case if the installed RAM is greater than 32-1.5 = 30.5GB. Approximately. Also you may need to have the remapping feature set on some BIOS.

- Gene

Quote: Originally Posted by GeneO

Quote: Originally Posted by LiquidSnak

Aftermarket GPU's have their own memory. The onboard graphics draw from installed RAM, usually.

They still use system address space. Their memory is mapped to a range of system system addresses. When OS reads or writes to that range, it translates to moving the data to/from the video memory over PCI-e or whatever bus.

The range of addresses that the video card memory is mapped are not accessible for other use. Hence if you have only 4GB of address space supported by your chipset and a video card with 1GB of on-board memory, you will have only have 3GB or less of useable memory.

Hmm... GeneO, yes my motherboard supports up to 32GB RAM. It means that the memory controller can address memory banks as many as 32GB at all times. There is no relation between my memory controller's capability to address these RAM banks with the MMU in my CPU. See, the governor of all is the CPU. It got MMU integrated to it (Memory Management Unit). This little bugger controls the memory controller on the chipset (in my motherboard) or controls it's own embedded memory controller (in case of Phenom/Nehalem-like processor). It only controls what it's directly connected to it, in this case - RAM. The local cache of a graphic card (graphic card's "RAM") is NOT controlled nor mapped by MMU. Here's the proof of my statement: open device manager, change the view to "Resource by type". That's the whole address space your computer can have. Look for your display adapter and watch it's memory address reservation. Here are mine:

Those are not 512MB times 3 (for 8800GT) nor it's 1GB (for GTX285).

If the case were to use a motherboard with onboard graphics,

Quote: Originally Posted by GeneO

Deacon,

I had tried to simplify my explanation and misspoke when I said the amount avail = max memory your MB support - video ram. It is max address space your chipset supports - video ram. The two are not always the same.

The latest Intel X chipsets have 36 bit (64GB) of addressing so this is no longer a problem.

Your statement is true, because the onboard graphics will reserve the main RAM as it's local cache, thus "max address space the memory controller supports - video ram = amount available to the system". But in the case of dedicated card, this statement is incorrect, as you can see in Device manager. These add in cards have it's own firmware, it's own governor, it's own memory table, in short, it's a "microscopic computer" attached to PCIe bus.

Edit: Btw, if you read ASUS's P5N32-E SLI's spec, it only supports up to 8GB RAM. That motherboard has the same chipset as mine...

Edit2: If you're interested, expand the memory part in Device manager, I'll be updating this post on this segment once I got my screenshots... Here's the screenshot:

000A 0000 - 000B FFFF = 131.071 8800GT
C000 0000 - CFFF FFFF = 268.435.455 GTX285
D000 0000 - DFFF FFFF = 268.435.455 8800GT
E600 0000 - E7FF FFFF = 33.554.431 GTX285
E900 0000 - E9FF FFFF = 16.777.215 GTX285
EC00 0000 - ECFF FFFF = 16.777.215 8800GT
EA00 0000 - EBFF FFFF = 33.554.431 8800GT

8800GT total: 318.898.172
GTX285 total: 318.767.101

Still not showing complete 1024MB + 512MB memory reservation...

Quote: Originally Posted by DeaconFrost

GeneO, your description of the issue in post #28 makes perfect sense, but I have never heard that in relation to the amount of memory a motherboard supports. That just seems strange to be discussing accessing memory beyong what is physically installed...such as the case above with 4 GB installed, and a 1 GB video board being present in the system. Again, I'm not saying you are wrong, but I worked for a major system builder for quite some time, and never heard of the physical limitations of the board having anything to do with how much of the physically installed memory can be accessed.

You're right all along, it is strange... Don't start doubting your self...

zzz2496

GeneO · 29 Oct 2010

I am afraid you are wrong zzz2496. Your memory doesn't "cache" your video RAM, it is directly mapped.

You are not looking at the memory address mapped for the device, but the IO register address Range. Go to the device manager, select your display adapter, select properties, then go to the Resources tab. You will see something like below. What you are looking at is the IO mapping at the bottom. Above that is the address range that maps to my video card and what takes up 0.5GB of my 4GB of memory. Some more advanced chipsets might make the remapping of the holes transparently, I don't know. But do this exercise and see if you have similar Memory range.

What you are looking at is Resources by type -> Input/Output (IO)
Instead look at Resources by type -> Memory to see how your memory is mapped to devices.

Note in the included jpeg there are two address ranges for my video card. D0000000 = 3489660928 and goes up to DFFFFFFF = 3758096383 and from 4024369152 to 4024434687 i.e., 512MB mapped to the upper part of my 4GB of address space. There is also a smaller reserved address range in low memory, not shown, for booting in low res graphics.

Edit, so I see your edit. Yes it doesn;t add up.

- Gene

zzz2496 · 29 Oct 2010

GeneO - I'm on it, will update this post once have everything...

I got the picture, it's the second one (I updated my post earlier, post 36), the one large Device manager screenshot. It shows me the exact memory maps/address reservation as your screenshot... But I'll post it for simplicity sake:

8800GT

GTX285

Both shows the same value as my earlier post... I'm still seeing around 400MB per card address mapped to my display adapter instead of 1.5GB... And on your screenshot (and your calculation): "D0000000 = 3489660928 and goes up to DFFFFFFF = 3758096383" = 268.435.455, not 512MB.

zzz2496

Darician · 30 Oct 2010

Whatever decision you make, the way I see it, you can never have too much RAM.

zzz2496 · 30 Oct 2010

Quote: Originally Posted by Darician

Whatever decision you make, the way I see it, you can never have too much RAM.

+1

zzz2496

Windows 7: 3 Gigs Ram or 4?

3 Gigs Ram or 4? problems?