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LAN Party Forums => General Discussion => Started by: _!Rathe!_ on May 07, 2007, 07:00:16 AM

Title: Max Memory. I didn't know this.
Post by: _!Rathe!_ on May 07, 2007, 07:00:16 AM

Here at work I copy a daily tip I get from a mailing list for all the users to read.  Over the weekend was one where I actually learned something.  Here is the tip.

Quote

Q. I have a new Windows Vista computer. I have the Ultimate version, with 4 gigabytes of RAM. However, when I look under System, it shows only 2.8GB of RAM. What happened to the rest of my memory?
Mike in Bloomington, IN, listening on WGCL 1370 AM

A. Sorry to say, I'm afraid you've wasted your money. The rest of your memory is sitting idle. Windows can't address it.
This is going to get a little technical. But it's important for people who want to build killer machines. Many motherboards will hold a maximum of 4GB of RAM. But that doesn't mean Windows can use it.

Let's get the math out of the way first. Windows Vista comes in two basic versions—32-bit and 64-bit. The biggest difference is the amount of address space each can access. The former can access 4GB of address space. The 64-bit version of Vista Home Basic can access 8 terabytes of address space. The other four versions can access 16TB.

(Mathematically, a 64-bit operating system could access 16 exabytes of address space. That's 4 billion times the 32-bit limit, give or take.

(All 32-bit operating systems have a 4GB limit on address space. It is imposed by mathematics. The problem is not limited to Windows Vista.)

OK, so let's get back to your question. You have 4GB of memory, but Windows only sees 2.8GB. That's because system RAM is only one thing vying for address space. Your machine has hardware that needs address space, too.

For instance, the video card is really hungry. According to Hewlett-Packard, a 256MB video card needs AT LEAST 256MB of address space. So let's say you build a big-time gaming machine. You install a 512MB video card. Throw in your PCI-E bus system and numerous other pieces of hardware. You could eat up half the address space.

Those pieces of hardware get the first bite of address space. RAM gets the rest. So, in that case, the 32-bit version of Windows would only access about 2GB of RAM.

How's that for a kick in the teeth? You spend a fortune for top-notch hardware, and inadvertently cheat yourself out of memory!

So, can you solve this problem with Windows' 64-bit version? Maybe, maybe not. The machine itself has to provide more address space. And you need a 64-bit microprocessor.

The latter is no problem. Both Intel and AMD make gobs of 64-bit microprocessors. Before you buy such a machine, though, make certain the chipset supports the additional address space.

Let's assume the machine offers tons of address space. In that case, all of the RAM would be fully utilized. But that's only if the application you're using (a game, for instance) is also 64-bit.

Unfortunately, almost all applications are 32-bit. That is certainly true of consumer applications. When they run on 64-bit Vista, they use emulation. This emulation is called Windows on Windows 64, or WoW64. And they can only access 2GB of RAM!

I'm afraid the consumer world just isn't ready for 64-bit Vista. It makes more sense in the corporate world. There, mammoth programs might exceed 4GB in size. With the extra memory accessible in 64-bit operating systems, these programs can be loaded into RAM in their entirety. That makes them run much faster.

In fact, we looked at servers on Dell's site. We found one option offering 32GB of RAM. That costs a mere $12,000 extra!

It looks to me like you're snagged, no matter what you do. Online, I found people whose machines accessed as little as 2GB of RAM. These people had 4GB of RAM installed. Needless to say, they were hot under the collar. But, like you, they have no realistic solution.

RAM is cheap today, so lots of people are interested in maxing out. But when I bought my Vista Ultimate machines, I went for 2GB. Frankly, that's a good number. It runs Vista very well. Much more, and I'd risk running out of address space.

Title: Re: Max Memory. I didn't know this.
Post by: zx2slow on May 07, 2007, 04:47:22 PM

Thats why I am running XP x64, all the x64 and memory addressing goodness without the overhead of vista.