[bld44]

I thought I would post this for anyone looking into ram. When I ordered some additional ram the other day (4GB), I was going to go with OWC until I found a great deal on Crucial at newegg ($43 per 1GB stick now gone). I had read into Crucial before and learned about the problems they had with their ram in a mac pro (recalled, different kinds, hard to find, all that mess). Well, it appears they finally got their act together. So don't let those old threads hold you back if you find a good deal on this stuff.

Here are some pictures. Note that the sticks without the Crucial stickers are OEM Apple sticks.





No problems so far with any errors or heat issues. They are running about exactly the same as the OEM sticks.

[mduell]

The issue with Crucial RAM in the Mac Pros was resolved and recalled before most other manufacturers and retailers were even shipping FB-DIMMs for the Mac Pro.

[Oisín]

Sorry to hijack the thread, but this is almost on topic:

I bought 4 GB of Crucial RAM a few weeks ago, too (2 x 2 GB, though, not 4 x 1). I got my Mac Pro today and promptly installed the extra RAM.

Initially (before I installed the extra RAM), the computer saw both 512 MB units placed in slots 1 and 2 on riser A, just fine. Then I put in the extra units, going by your instructions (mduell) in the "Where to get Mac Pro RAM" thread, both risers identically set up with a 2 GB Crucial unit in slot 1 and a 512 MB stock unit in slot 2. Machine sees only 2 GB, placed in slot 1 in riser A.

I tried switching, so the stock units were in slots 1 and the Crucial units in slots 2—that made it see only 512 MB. So it only sees the unit in slot 1 in riser A.

I've since been led to believe that there's a difference between how pairing is handled in G5s and Mac Pros, so that pairs should be serial, rather than parallel (can you call it that?). So, I should put the Crucial units in slots 1 and 2 in riser A, and the stock units in slots 1 and 2 in riser B for it to work.

I tried finding something on that here, but my search-fu is as always completely useless, so I couldn't. Is this true?

(I'm at work now, so I can't just try it and see if it works—would be neat to have some kind of confirmation beforehand, then I'll know the machine won't blow up or steal my cookies when I try it once I'm home)


Edit: Never mind—just because my Google-fu sucks doesn't mean others' does. Got confirmation right here in the meantime!

[mduell]

Originally Posted by Oisín 

Sorry to hijack the thread, but this is almost on topic:

I bought 4 GB of Crucial RAM a few weeks ago, too (2 x 2 GB, though, not 4 x 1). I got my Mac Pro today and promptly installed the extra RAM.

Initially (before I installed the extra RAM), the computer saw both 512 MB units placed in slots 1 and 2 on riser A, just fine. Then I put in the extra units, going by your instructions (mduell) in the "Where to get Mac Pro RAM" thread, both risers identically set up with a 2 GB Crucial unit in slot 1 and a 512 MB stock unit in slot 2. Machine sees only 2 GB, placed in slot 1 in riser A.

I tried switching, so the stock units were in slots 1 and the Crucial units in slots 2—that made it see only 512 MB. So it only sees the unit in slot 1 in riser A.

I've since been led to believe that there's a difference between how pairing is handled in G5s and Mac Pros, so that pairs should be serial, rather than parallel (can you call it that?). So, I should put the Crucial units in slots 1 and 2 in riser A, and the stock units in slots 1 and 2 in riser B for it to work.

Noooooooo! I hope I never said that.
The memory needs to be installed in pairs on each riser. So you'd put the 2 Crucial modules on the inner two slots of one riser, and the 2 Apple modules on the inner two slots of the other riser.

Originally Posted by Oisín 

I've since been led to believe that there's a difference between how pairing is handled in G5s and Mac Pros, so that pairs should be serial, rather than parallel (can you call it that?). So, I should put the Crucial units in slots 1 and 2 in riser A, and the stock units in slots 1 and 2 in riser B for it to work.

The Mac Pro has 4 memory channels (in parallel), each of which supports 2 modules (in serial). With 4 modules you've placed one in each memory channel.

[Oisín]

Originally Posted by mduell 

Noooooooo! I hope I never said that.
The memory needs to be installed in pairs on each riser. So you'd put the 2 Crucial modules on the inner two slots of one riser, and the 2 Apple modules on the inner two slots of the other riser.



The Mac Pro has 4 memory channels (in parallel), each of which supports 2 modules (in serial). With 4 modules you've placed one in each memory channel.

It's quite possible you never said that, actually. I had to read your posts four times to be (what I thought was) sure I got it—apparently, I didn't.

I'm a bit unsure about how exactly you mean the four memory channels each supporting two modules, though. One memory channel consists of two adjacent DIMM slots on the same riser? So riser A, slot 1 and 2 is one memory channel and 3 and 4 is the second memory channel?

And by placing the units the way I did, I have one of each kind in both memory channels I've used? Is that what you meant? If so, then that makes sense. If not... then I'm loster than I thought

(I just thought of this, too: in the example you were talking about in the other thread, the guy had bought 4 X 1 GB, so when you told him to put them in slots 1 and 2 on each riser, they would still be in serial pairs, so both filling up a memory channel. That would explain how I extrapolated wrongly from your post that I was meant to pair them parallelly.)

[mduell]

Originally Posted by Oisín 

It's quite possible you never said that, actually. I had to read your posts four times to be (what I thought was) sure I got it—apparently, I didn't.

I'm a bit unsure about how exactly you mean the four memory channels each supporting two modules, though. One memory channel consists of two adjacent DIMM slots on the same riser? So riser A, slot 1 and 2 is one memory channel and 3 and 4 is the second memory channel?

Nope. They've wired the riser so slot 1 and slot 3 are on the same channel. So with a module in each of the first two slots, you're using both channels available on that riser.

[Oisín]

Aha. I see.

So I should put the Crucial RAM in slots 1 and 3 on riser A, and the stock RAM in slots 1 and 3 on riser B, then?

[bld44]

Go by this: http://homepage.mac.com/tribe3/.Pictures/MemConfig.jpg

[Oisín]

So... Slots 1 and 2, then, not 1 and 3?

I get off work in six minutes now, so I'll check it out when I get home. I can see what works and what doesn't, then.

But thanks for the help, both of you

[Oisín]

Right. Tried slots 1 and 2 first, and it worked perfectly. Thanks, mduell, and thanks bld44!