testing memory

[ZMacintosh]

Waiting for the 27" iMac to arrive sometime at the end of the month, picked up a great deal on 16GB of memory for the iMac. However wanted to test it before it got here in the event they were DOA.

The only other machine I can use to test is a 2009 13" MacBook Pro that supports DDR3 PC-8500 1066Mhz and the new modules I have are 4GB (x4) DDR3 1333Mhz modules.

would I get an accurate reading if i tested them out in the 13" 2009 MBP? or will there be expected errors?


thanks!

 

[Makosuke]

For the most part, faster RAM will work fine in a machine with slower minimum requirements, so long as they're both DDR3 (or DDR2, etc); certainly, if it works at all, errors in one machine will show up in another. I suppose I could imagine a theoretical case where some, say, 1333MHz RAM would work ok when running at a slower 1066MHz but show occasional errors at 1333MHz, but I've never personally seen that happen in the real world, and I doubt it's likely.

I will add, however, that I learned recently it is possible to have DDR3 RAM that won't run at a slower speed. OWC's 1333MHz DDR3 Mac RAM, according to their tech guys, ONLY has firmware for whatever speed it's sold as, so if you try to use it in a Mac with a slower bus, it won't work. OWC is the only manufacturer that I'm aware of that does this, but there may be others.

 

[ZMacintosh]

oh okay, because the ram is 1333mhz (corsair) and the 2009 reads it as such 1333Mhz and two sticks from the AHT and one stick in REMBER came up with errors but was fully recognized by the OS and activity monitor.

so im kind of uncertain what that might entail

 

[Makosuke]

If it's showing errors in rember, unless that app is misbehaving terribly, it's DoA. The case I mentioned of incompatible speeds would mean that the RAM wouldn't be recognized at all, period. If it shows up, it should work with no errors, period.

It's theoretically possible that the RAM is very low spec and therefore compatible with a Mac, period, but I'd expect it to just not work in that case. Since one stick worked, it's far more likely that it's just bad RAM.

If you want to back up rember's conclusion, boot into the Apple Hardware Test disc that came with your Mac and see what its long test comes up with.

 

[ZMacintosh]

strange because some sticks were throwing up errors on the 2009 MBP which require 1066mhz and when a friend let me test them in his 2011 15" MBP which require 1333Mhz (same as iMAc) no errors were thrown up and worked just fine.


so im wondering if the clocking speed wasnt as efficient and the compatibility wasnt 100%?

 

[Makosuke]

Well, it's theoretically possible that the 1066MHz firmware on the RAM doesn't meet Apple's spec (or is funky), hence the errors, while the 1333MHz firmware is fine. I'd be very suspicious of that stick, though, particularly if another stick that should be the same is behaving properly.

This is one of the reasons I always buy OWC or DMS RAM--in addition to the lifetime warranty it's guaranteed to work in the Mac I bought it for, so there won't be any questions of compatibility or support.

 

[ZMacintosh]

Well it looks like the memory is fine, i stress tested it plenty of times with rember and AHT on overnight loops, extended test, etc.

It might have been picky with the 2009 13" but checked out 100% individually on each stick and in pairs in my friends 2011 MBP 15".....so, so far so good.

i just rule it to the 2009 MBP being picky with the memory.