Why would one of my RAM bays be okay with a 512MB stick but not a 2GB?

February 11, 2011 9:10 AM

I got some new RAM for my Macbook, but it's causing some really weird freezing issues.

I recently tried upgrading the RAM in my Macbook from 2 512MB sticks to 2 2GB sticks, ordered from Crucial.com.

I upgraded, and everything was working fine for about an hour, when the computer froze. I rebooted, and about 20 minutes later the computer froze. I took out the RAM, reseated it, and tried to restart. The computer froze with the little spinny-wheel telling you that it's booting up OS X.

Then! We took out the 2GB sticks and replaced it with the 512MB sticks - everything was working fine. Put the 2GB sticks back in, it froze during bootup.

Put in one 2 GB stick and one 512MB stick and the computer froze during bootup. Switched the bays they were in and it's been working fine ever since, with 2.5GB total. Switched them back and yes, it froze again.

So, as far as I can tell, the problematic combination is a 2 GB stick + the left-most RAM bay (it's on the left when you're holding the computer horizontally and the battery is on upper half - just in case First Bay vs. Second Bay would matter for some reason). No matter which 2GB stick you put in there, it freezes on bootup.

To further complicate things, I never looked at the RAM listing when it was first working to make sure it was reading a full 4 GB - maybe I just hadn't seated the 2 GB stick in the 'broken' bay, so it never worked in the first place.

So yeah, my Macbook is out of warranty and it's a pretty weird situation. Before I take it to the Genius Bar and have them offer a $1000 fix, any ideas would be appreciated.

posted by jenmess to computers & internet (10 answers total)

If I were you I would try to exchange the Crucial RAM sticks. Get two new ones and if it still doesn't work you could try a different brand. I've always had good luck with house brand RAM from OWC.

If neither of those work, it may be time to check out the Genius Bar.
posted by crosbyh at 9:20 AM on February 11, 2011

You've already done the hard work. Your problem is either:

1) the RAM you received is marginal and should be replaced with known-good modules.

or

2) the left RAM slot is damaged or malfunctioning when 2GB modules are used (the only fix for this, unfortunately is a new logic board ($749 stock; $349 exchange) which isn't worth it)).

If I were you, I'd return the RAM and get new modules. If it continues to lock up even on your 3rd and 4th module in the left slot, then you have a pretty clear answer as to where the problem lies and can make you decision then.

Or live with 2.5GB or 3GB of RAM. Good luck.
posted by mrbarrett.com at 9:21 AM on February 11, 2011

Agree with crosbyh.

Also make super sure that you got the recommended RAM speed, timing, type, etc. An old system of mine would work with high speed RAM, but not for very long and not with every RAM slot populated.
posted by aerotive at 9:23 AM on February 11, 2011

The RAM is probably just flaky. Another thing you should look at is whether the hardware of your macbook can address 4 gb of ram. Mine (summer 2006) can only handle 2 GB, and then for a while, they could deal with a 2 Gb and a 1Gb stick, and then it has gone up from there.

The OWC upgrade matcher can let you check for how much RAM you can actually buy.

Macs can be picky about their ram type (it makes the system stabler overall), so be sure that the RAM is the right type as well, like aerotive said.
posted by rockindata at 9:50 AM on February 11, 2011 [1 favorite]

Seconding the fact that older macbooks can't handle more than 2GB of RAM.
posted by wayland at 10:51 AM on February 11, 2011

Bad RAM is not uncommon. The folks you bought the RAM from know this. Just exchange it and try again.
posted by mmdei at 10:59 AM on February 11, 2011

If you want to see if the RAM is bad, you can try testing it by burning an ISO from MemTest86 and booting that up.
posted by thewumpusisdead at 11:45 AM on February 11, 2011

Your mac mobo might just not be able to handle more than 2 gb of memory. My 2006 MBP maxes out at 2gb.
posted by thsmchnekllsfascists at 11:47 AM on February 11, 2011

Depending on the model of the Macbook you have, it may not support 2 x 2GB.

What's the model #? Apple menu/about this Mac/More Info -- Model Identifier.

I have an original model MacBook (white one) that won't work with 2 x 2GB, but works fine with a single 2GB, or a 2GB + a 512GB stick.
posted by MiG at 12:30 PM on February 11, 2011

Thanks everyone! It's a MacBook3,1 and definitely supports 4GB. I think we'll just go ahead and exchange it in the hopes that works.
posted by jenmess at 2:43 PM on February 11, 2011