Hello,
I've just received and installed my new memory.
Here is the current set up:

Primary Slots: 2x 1GB Corsair 800mhz XMS2 DDR2 800MHz/PC2-6400 XMS2 Memory Non-ECC Unbuffered CL4(4-4-4-12)

Secondary Slots: 2x512mb Ebuyer Extra Value 800mhz Memory

My pc is noticeably faster already; the low memory was really letting my system down. I now have a unusual combination of ram i plan to eventually (when i get the cash) buy another 2GB corsair kit and fit that in the secondary slot instead of the crappy ebuyer ram.

My main question is whould my pc function much better with 4GB instead of 3GB + i understood that identicall ram functions better together eg. all 1gb modules. Would my pc be better of without the ebuyer ram installed for now and just the 2gb corsair?

Thanks in advance for your help,
Will

You probably won't see any benefit to moving to 4GBs, but that needs to be qualified. I am assuming you had the 2x512MB originally, and just installed the new 2GBs of ram. If so, your ram usage was more then 1GB. The question then becomes, do you use more then 3GBs? The answer for most is probably not.

The other issue then becomes what OS do you have. If you have a 32bit version of windows, you are pretty much at the max of what you can run anyways. The OS needs to set aside memory address space so it knows whats in your video card(s) memory, harddrive's cache, etc. It also needs some address space to "talk" to the northbridge. Because of this, about 500MBs or so is set aside, more if you have a 512MB video card or higher. (the more video ram, the less RAM you can use.) Many people who install 2x2GBs of ram say they can only use about 3.2GBs of it.

Its for this reason I would think you shouldn't buy any more ram. Unless you have Windows Vista/XP 64bit, you can't use any more ram. As long as things are working ok, just leave well enough alone.

Thanks very much, im on windows xp (i don't like vista and it slows down the pc so it dosen't seem like much of an 'upgrade') So i'll leave the ram until i move to a 64bit os.

Cheers,
Will

The short answer is: You have 3GB of RAM and your computer is working fine. Declare victory and move on to something else.




But on the small chance you want the details why I made the above statement:

32 bit operating systems have 4GB worth of address space, and everything on your system needs an address before the OS can "talk" to it. This includes more items than simply system RAM - The system BIOS needs some, certain motherboard resourcess need addresses, mapped I/O, plus whatever addresses need to be assigned to your PCi slots, plus whatever devices you have plugged into those slots (Video RAM being a huge consumer), plus peripherals... All of those addresses come out of the 4GB bucket *before* the OS assigns addresses to your system memory. So if you install 4GB worth of system memory, your computer will display and use less - usually somewhere around 3GB.

Why is it that way?? Well.. If you assign addresses to RAM first and run out, then your computer won't work since the OS cannot communicate to the subsystems I listed earlier. If the OS runs out of addresses before fully assigning system memory, all the happens is the un-addressed memory won't be used.


You can get around this limitation by using either a server based OS (NT, Server 2003, Server 2008) which supports "Physical Address Extensions" - basically an added table. But this requires the use of device drivers which are "Large Address Aware" - and most mass market (consumer) ones are not. Or you can use a 64 bit (XP64 or Vista 64) operating system, as these are mathmatically capable of supporting up to some Exabytes (thousands of GB) worth of address space - Though the Windows versions are currently artificially limited to between 32 GB and 128GB. Matters not tho, since consumer based mobos currently only support up to 8GB.


Why would you 'need' that much RAM?? Not for too much now, since most applications only support 2GB of space themselves (meaning even if you have a Metric Sh*tTon of RAM, the application itself only understands and will only use 2GB). There *are* apps which will use more - Some of the newest games (Crysis and CoH, for example), and some of the more serious home applications - Video/Picture editing etc - can/sill use more RAM if it's available to them. But that's only looking at one app - More RAM will let you run more programs at the same time without having to page data to and from your hard drive. What that means in real terms is you can run a lot of stuff (play a game, listen to music, encode a video, and have a load of browser windows all at once) and still be able to Alt/Tab between them quickly. And if you have the processor for this kind of abuse (read: "Quad" ), then you can do so with minimal negative impact on how fast those apps are running - In English, with such a setup you can do all that stuff at once and still get (nearly?) all of the Frames Per Second in your game. Once you're at speed, adding memory won't make things any faster than they would be by themselves. But it will allow you headroom to do more stuff at once before the system shows signs of slowing down.



(can you tell I'm not keen to start work this morning???)

Why oh why did you not spend the extra £10 for the corsair modules... I had some ebuyer memory - ended up in the bin it was so bad...

The only reason I can think of where moving up to 4Gb would be helpful in your setup is that it would probably stop your system from ever paging to the hard drive.

Kudo's to Scotteq for a pretty fair explanation as to why I have a quad with 4G of ram!

yea the ebuyer mem IS ****, i was strapped for cash at the time and needed some ram quick. oh well. **** ebuyer.

Test your setup with memtest86+, to be on the safe side.