RAM fails in pair, but works individually?

[misterwhy]

I have a MacBook that was exhibiting a startup-beep with three repeating short beeps, which a search indicated is caused by RAM issues. It's an older machine running Snow Leopard with 1GB of RAM (awful, I know, but this was a budget college machine and I've since upgraded to 4GB on a newer MBP).

I re-seated the RAM sticks, same issue.
Tested each stick in each slot, and the machine starts up fine with only one stick installed. Both slots work with both sticks, just only one at a time.
The pair won't work, no matter how I switch them up.

What could this be caused by?

 

[jamesjingyi]

What are the specs of the ram and the machine... maybe the machine cannot handle too much... I know my macbook will take 4GB (2x2GB) but only supports 3.3GB.... I use it like this.... yours may not be able to support this tho..

 

[misterwhy]

What are the specs of the ram and the machine... maybe the machine cannot handle too much... I know my macbook will take 4GB (2x2GB) but only supports 3.3GB.... I use it like this.... yours may not be able to support this tho..

I didn't change anything. The machine was unused for about a year, sat in a box in storage. When you say "cannot handle too much," this is the RAM pairing that was in the machine for years.

Anyway, the RAM sticks are Samsung 512MB DDR2 667, 200-pin SODIMM. But these were in the machine for a long time and worked fine. Question is why they will no longer work together.

More important (to me, ) question: if I just go buy new RAM, does it sound like it'll work? I don't want to go buy something and find out it's a logic board issue or something else. I can get 2GB of RAM at Fry's nearby for $30, which is fine--just don't want to waste my time.

 

[jamesjingyi]

Sorry for the late reply,
You have to be careful to buy the right mhz... Too large and it'll not work. Too small and it'll work but might not be worth the upgrade... Check the number of your macbook e.g. macbook 2,1 (My blackbook). Ram should work when you stick it in... check the mhz on both the rams and see whether they are too big... otherwise, return and try again... maybe faulty ram... what macbook (2,1 5,1 e.t.c)? This will help tremendously...

Oh and btw, I'm 15, so I'm trying my hardest!

 

[misterwhy]

Sorry for the late reply,
You have to be careful to buy the right mhz... Too large and it'll not work. Too small and it'll work but might not be worth the upgrade... Check the number of your macbook e.g. macbook 2,1 (My blackbook). Ram should work when you stick it in... check the mhz on both the rams and see whether they are too big... otherwise, return and try again... maybe faulty ram... what macbook (2,1 5,1 e.t.c)? This will help tremendously...

Oh and btw, I'm 15, so I'm trying my hardest!

This is the model of Macbook: http://support.apple.com/kb/SP5

Still have no idea what is up.