Issues upgrading RAM on unibody Macbook Pro

[hellisforheroes]

Recently got 4GB of RAM upgrade (not from Apple store) The RAM is DDR3

Tried to upgrade my MBP but when both chips were installed the computer wouldn't boot (made a beeping noise) tried it with one of the 2GB chips and one of the standard ones (1GB) and it booted fine.

The system now says (via 'about this Mac') that it has 3GB of RAM with these mismatched chips installed and seems to work fine - so does anyone know why it won't boot with both chips? - and does this mean that it is actually only using 1GB now as it doesn't seem to like the new chips.

Anyone else had a similar experience?

The stickers on the new RAM read:
2GB PC3 - 10666
1333 MHZ DDR3

If that is any help.

Thanks in advance for your help!

 

[steveza]

Doesn't the new MBP take 1066MHz RAM and not 1333MHz?

 

[Sneakz]

Yeah, its probably because your chips are trying to run at 1333MHz which the MacBook Pro cant handle. When you use one of your existing DIMMs, it runs at the lowest common denominator, which is PC3 8500. That's why 3GB works and not the four.

 

[electrolux76]

It could also be a bad stick

Try both sticks of your new ram one at a time. See if one works and the other dosen't. The speed difference shouldn't be that much of an issue, the ram should just clock down to the bus speed.

 

[Bill Gates]

It looks like the memory you purchases is mismatched; correct me if I'm wrong. These computers run the memory in dual-channel mode, which is very sensitive to the memory installed. As to what Sneakz said, the memory won't "try" to run any faster because the memory speed is set by the system. However, the table indicating latencies may be different and therefore causing problems. If I were in your position, I would try to obtain a refund on one or both modules, and get a matched pair, or if unavailable, two modules of the exact same type.

 

[hellisforheroes]

Thanks for the replies.
So, it seems that due to the speed difference it's incompatible. Will it do any damage (or is it just a bit pointless in terms of performance) to run mismatched modules. Think i might try and get a refund but if that fails then i'll just carry on using the 3GB of RAM (if there is no harm) - What was said sorta makes sense -if it is running on the lowest denominator in the case of two different modules- but i guess that means that the system doesn't decide the speed, but the modules themselves.

 

[Bill Gates]

It may or may not be the speed difference that's the issue. It is probably just due to the fact that they are different modules and won't play nice with each other. If your factory RAM works with the one module, then it won't cause any harm. Mismatched modules don't harm anything.