Any idea why http://support.apple.com/kb/HT4433#3 and Memory Slot Utility differ?

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Level 1

8 points

Any idea why http://support.apple.com/kb/HT4433#3 and Memory Slot Utility differ?

Hi,

According to Apple, at http://support.apple.com/kb/HT4433#3 , adding memory to a Mac Pro (early 2009, eight core (two quad-core))

is done by pairing the SIMMs (e.g., slots 1&2, or 3&4).

But...

when I install 4, 4, 2, 2 in one module, and 2, 2, 2, 2 in the other, the system boots ok and the Memory Slot Utility pops up saying it should be 4, 2, 2, 2 and 4, 2, 2, 2 (which I'd expect, based on mainframes I've worked on elsewhere!).

If I change the memory to match the MSU, everyone's happy (except the manual writers).

Any idea why the manual doesn't require balanced loading? (E.g., was this a quirk of the 2009 Mac Pro and earlier/later ones require the "pair them up" approach (and the manual wasn't updated)?

Or?

Just wondering (question arose when I tried to install two 8 GB DIMMs ... giving up for now, suspect they didn't play well with existing DIMMs)

thanks,

Stan

Mac Pro, Mac OS X (10.6.8), Adding memory, memory slot utility

Posted on Feb 28, 2013 4:28 PM

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Answer 1

Feb 28, 2013 5:19 PM in response to sieler

Mac Pro (early 2009

You are referring to the wrong section of the manual. The section of the manual requiring pairs is for a Mac Pro with removable daughter-cards -- the previous generation of Mac Pro (2008 and previous) which uses paired DIMMs in adjacent slots.

Your Mac Pro features slots 1,2,3 as free and independent slots, while slot 4 is shared with slot 3. (and same on the other side)

The correct diagrams are there, but you have to dig carefully to find them. Look for the tag:

In an 8-Core Mac Pro (Early 2009)

then be very careful not to scroll down too far, or you end up inside the guts of the 2008 model with the removable cards.

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Answer 2

sieler Author

Level 1

8 points

Feb 28, 2013 6:20 PM in response to Grant Bennet-Alder

Thanks, Grant!

I'd missed that expandable section *every* time I read that page!

BTW, the primary difference is that the expandable section doesn't stress "paired" quite as much ... it still implies slots 1,2 would be used by a pair, not 1 & 5 ... but, its saving grace for accuracy is that it does mention the Memory Slot Utility:

"Note: If you install different-size DIMMs in your Mac Pro, follow the order in the table. If the DIMM configuration you install doesn't provide optimized performance, the Memory Slot Utility should appear onscreen and recommend an improved configuration."

One way to read that is: there are a lot of variables here ...rather than try to describe them, we've written a utility to check and tell you what to do. I have no problem with that, just wish it had been a tad clearer (and a tad easier to find!)

thanks again,

Stan

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Answer 3

Feb 28, 2013 6:27 PM in response to sieler

Don't take the maximum sizes they say as gospel, either. You can easily install 8GB modules, and if you are willing to toss all others out, you can install 16Gb modules.

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Answer 4

sieler Author

Level 1

8 points

Feb 28, 2013 6:39 PM in response to Grant Bennet-Alder

Yes, I'd found that out on several web pages.

As it happened, I was trying to add two 8 GB DIMMs from Kingston (KVR10R7Q8K2/16I) . They're RDIMMS, if that matters.

By themselves (slots 1 & 2), they work. Once I added any of the existing DIMMs, POST failed

with blinking light (no audio was available to listen to).

(they'd have taken me from 20 GB to 32 GB, the ostensible max for Snow Leopard, IIRC)

thanks again,

Stan

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Answer 5

Feb 28, 2013 6:48 PM in response to sieler

The Mac Pro has a complex sound output system. The Power-On Self test tend to flash silently on the Mac Pro, while it beeps like crazy on the MacBook pro.

Kingston should know better.

Buy from a Vendor who says:

"It works in your MAC,

or your money BACK."

I don't think you are anywhere near the limit for Snow Leopord.

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Answer 6

Feb 28, 2013 7:24 PM in response to sieler

sieler wrote:

...They're RDIMMS, if that matters...

It does. The "R" means they're registered and they're incompatible with non-registered DIMMs. Either is OK, they just can't be mixed. I almost fell into that trap myself. There's a good explanation here http://en.wikipedia.org/wiki/Registered_memory. Note the benefit of registered DIMMs when all the slots are filled.

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