Helping people with computers... one answer at a time.

Depending on your computer you may be able to mix and match RAM chips of differing sizes. Or you may not.

I just purchased 1 gigabyte of RAM for my computer and it works great. What didn't work was trying to use my previous 2 256MB ram sticks in combination with my new 1GB Stick. Is there any way to make this combo work? Perhaps a specific order to install the RAM?

The short answer is: maybe.

On some computers you can, and on others you cannot. On some you can, if as you suggest, you do it "the right way". So how do you tell?

It really all depends on how the computer's motherboard is designed. The definitive answer comes from your computer manufacturer. My first step is always to visit the support web site for that specific computer and see what's available, and how memory can be configured.

"The 'problem' is simply that different computer motherboards can accept memory in different, but specific, combinations."

Another good resource is I've purchased memory from them a time or two, and they have a fairly helpful compatibility identifier which can step you through the process of selecting the proper memory for your computer.

The "problem" is simply that different computer motherboards can accept memory in different, but specific, combinations. Some examples:

  • Some require that all memory sticks in the computer be identical. So if you have four slots, you can have 4x256meg, or 4x1gig, but you can't mix the 256meg and 1gig sticks.

  • Some allow you to mix, but you must mix in pairs. Meaning you might be able to have 2x1gig and 2x256meg.

  • Some require that if you mix, you must do so in a certain sequence. So you might be able to put 1gig in slot 1, and 256meg in slot 2, but not the other way around.

  • Many require that if you mix (according to whatever other rules there might be), the memory sticks share certain other characteristics, such as speed or others.

As you can see it's not a simple yes you can, or no you cannot. It really does depend on the machine you're dealing with.

Article C2683 - June 9, 2006 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

June 9, 2006 6:53 PM

Some more... If I'm not wrong, there's nowadays, some card to extend capability ram memory, using board slots. Think the problems is, how much memory can I add? It depends of board used! Am I wrong? Tks. Vic-Lxa-PT -

Greg Bulmash
June 10, 2006 8:17 PM

Whether or not your motherboard explicitly requires you match speed and latency on memory sticks, even if they're different capacities, match them anyway.

There are three things where seeking bargains can lead to long-term regret... Doctors, shoes, and RAM.

June 13, 2006 6:21 PM

It really depends on the speed when it comes right down to it. If you using 1 stick of 128 with a speed of can "trick" your sytem by putting in another stick of 128 to increase your memory with another speed, such as 133mhz, but you have to put the faster stick into DIM2 verses DIM 1...and your system will "think" it's all running at the slower speed. The reverse is not true thou. Always put the faster speed in the second slot, and it whould be fine. Not always, depending on the MB, but I have found sucess in doing that.

David Bowman
April 8, 2010 2:34 PM

I have a Dell Dimension E520 with Vista 32, which has a maximum RAM addressability of 3.1G as I am told by Dell and Crucial. Had 1G in each of the #1 and #3 slots and a 2G stick (also a different speed) in the #2 slot. Worked well for awhile but now it's acting like it's running on 500K total RAM. Crucial says each of the 4 slots can only have 1G apiece. Dell is not sure (thanks, guys). I'm going to try that. I suspect the matching issue is a factor here, so double-check with the manufacturer if that's required.

May 19, 2010 4:57 AM


October 22, 2010 3:53 PM

Leo, is it true that if you have two memory sticks installed, each with different speed, then both will operate at the slowest speed installed? Also, which is better performance wise, having one 1GB stick installed or having two matching 512MB sticks installed? Thanks

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