A Quick Question on RAM and 32-bit OS

[Rl'Halsinor]

I know XP can only utilize 3 gigs of RAM. If your system can run dual channel in a 2x1 gig configuration and you add a third 1 gig stick does your system lose the dual channel aspect?

What is gained or lost with 3 gigs?

Thanks.

 

[DarkKestral]

I know XP can only utilize 3 gigs of RAM. If your system can run dual channel in a 2x1 gig configuration and you add a third 1 gig stick does your system lose the dual channel aspect?

What is gained or lost with 3 gigs?

Thanks.

OK, for a PC to work in the fastest mode you have to have identical sticks of the same size and type in each set of 2 slots. The advantage is that the memory controller can utilize tricks to increase overall RAM speed.

However, that doesn't mean you can't have mis-matched sticks, or uneven numbers of sticks; rather it just means you'll be somewhat slower. How it will fare for you depends on a number of factors. These factors basically come down to "where's your bottleneck?" If RAM speed is your bottleneck, then you will likely have to move to either faster RAM, or if it's capped in speed by the motherboard, a new motherboard (at which point it may be better to buy an entirely new system) If RAM size, but not speed, is your bottleneck, then performance is likely to increase, despite the slower RAM speed. If RAM is not your bottleneck at all, then it may have no apparent effect.

Alternatively, if you want more RAM but want to keep dual-channel mode going, you can use either 4x1GB or 2x2GB. Which is better will depend on the motherboard you have and the RAM you can purchase. A single stick of a older model of RAM may cost more than 2 newer, larger sticks, for example.

Plus, the thing is, even if your copy of WinXP can only address something like 3.3 GB, you can still get some extra performance by going to the 4GB wall.

 

[azhrei_fje]

I know XP can only utilize 3 gigs of RAM.

Check out this page on microsoft.com as it discusses memory management in Windows (or what MS calls "memory management" ).

There is a link at the bottom of the page for "4G Tuning". After you finish reading this page, jump to the Tuning page where there is more goodness.

All that said, install Linux (32-bit or 64-bit) and avoid the nastiness that is Windows. (Of course, most people claim they are so hooked on games that they'll put up with it. Sad, actually. )

 

[Aus_Snow]

Dual channel's pretty insignificant in the first place. Don't worry about it. Depending on the stuff you run, you'll see a hell of a lot more improvement from simply having 3GB than from 2GB being in dc mode.

Personally though, I would did go with a 2x2GB kit, even though not all of it gets accessed by Windows. Works great!

 

[Thanee]

32-bit OS can address 4 GB of RAM, but some of it is reserved for graphics memory and so on.

Considering RAM prices, right now I would simply get 2x2 GB kit, can't go wrong with it.

It's generally best not to mix RAM of different sizes/brands and use no more than 2 modules in total.

Bye
Thanee

 

[Steel_Wind]

A 32 bit OS, be it XP or Vista, can use 3.45 gig of RAM memory address space.

It's not a defect, it's the inherent limitation of 32 bit math. That's a finite number. More finite than we would prefer it this juncture.

 

[dvvega]

In general you will find Windows XP only using 2 GB for you ... most of your extra GB will be secretly eaten by the OS itself.

Upgrade to 64 bit XP if you can, however you will lose some games compatibility.

D

 

[drothgery]

Okay, trying to clear up a lot of misconceptions here...

For a longer version, with a lot more details, which will also mention some edge cases I'm ignoring here, look at this ArsTechnica forum thread

1. A 32-bit OS has 2^32 bits of address space, or 4 GB, available.

2. Many devices, most notably the video memory in your video card, are mapped to some of that address space because memory-mapped I/O is much faster than any other means of communicating with them. If address space is used by devices, then the memory that would correspond to it cannot be used. This is why you won't see all 4 GB you have installed under 32-bit desktop Windows.

3. Desktop versions of 32-bit Windows allow any single application to use up to 2 GB.

4. Although almost all current CPUs support 'PAE' which allows 36-bit memory addressing, a lot of 32-bit drivers have issues with being mapped to memory above 4 GB. So only server versions of 32-bit Windows support this feature (which allows up to 64 GB of address space).

5. By far the best option, if you have 4GB+ of RAM and want to use all of it under a desktop version of Windows, is to get 64-bit Vista. It has much better driver support than 64-bit XP, hacks to enable accessing 4GB+ in pre-SP2 versions of XP open up gaping security holes, and even if server versions of windows weren't unsuited to gaming use, legit copies are expensive.

 

[Rl'Halsinor]

I really do appreciate everyone responding. I've learned some new things and that is always good. Perhaps my system specs might lend you guys to give me a more definitive answer. I am in no way challenging what you wrote but what I am looking for is, in your opinion, either a yes or no; like, "Yes, after reading your system specs it would probably be a good idea to get another 2 gigs," or "No, it would be a waste."

System Specs for my Socket 939

EPoX 9NPA+ Ultra nForce 4 motherboard - I did a lot of research before buying and it is one of the stablest boards I have ever worked on. It has the latest and last BIOS ever made for this board.

Memory - This is in a 2x1 gig configuration: Newegg.com - OCZ Platinum 2GB (2 x 1GB) 184-Pin DDR SDRAM DDR 400 (PC 3200) Dual Channel Kit Desktop Memory - Desktop Memory

OS - XP Pro w/SP 2

CPU - Athlon 64 dual core 3800+ Manchester @ 2.0 GHZ

Video Card - Nvidia 9600GT 512MB/256bit/GDDR3 PCI-E 2.0

HD - Seagate SATA 7200 8mb cache

As much as I would love to build a new system this one is going to have to do me for a long time. I have seriously thought about Vista 64-bit but Windows 7 is less than a year away.

Also, I belong to a tech forum that deals with helping people who have BSODs, hardware, and software issues, etc. I have noticed a good number of people who come there who experience issues when there is 4 gigs of RAM and XP and a number have the 2x2GB configuration. Often they find stability when they just run with 2 gigs. If I decide to go with another 2 gigs what should I do to prevent instability?

One other question. I know that XP with 4 gigs will take a good bit of the memory and apply it to the video card. Is this "wasted" or actually put to good use?

Thanks for reading this.

 

[drothgery]

Basically, 32-bit XP with 4GB of RAM installed means that ~1 GB will be 'wasted' (it will depend on your exact system configuration, mostly your video card) in that your video memory and other devices will 'cover up' that memory and keep the OS from being able to access it.

But there shouldn't be any real problem with 4 GB of physical memory under 32-bit XP, it just means you've got 1 GB you can't use. Any instability issues with 4 GB that were resolved by dropping down to 2 GB were almost certainly specific to motherboards, and I'm not an expert on that.

I mean, in my case, I ordered my PC with Vista x64 and 4 GB pre-installed.