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My DIMM Riser A (Mac Pro) has 'Disappeared'!

spetznatz

spetznatz

macrumors regular
Original poster
Just bought 4 x 2GB modules, installed them on both risers, in the first two slots.Remaining slots are filled with 4 x 1 GBs.

Restarting, check 'About This Mac...' it reports 6 GB instead of 12 GB.

Using ASP, it reports that DIMM Riser A 'Empty' for every slot.

I've re-seated the riser, same thing. I noticed that the red LEDs flashed on both risers when I started up...so both are getting juice.

Anyone have any idea what's going on?

TIA,
 
That happened to me once. Try restarting and holding down Cmd+Alt+P+R when it 'bongs', keep that held down until it 'bongs' again. Let me know if that works 🙂
 
Cheers, both --

I'm going to run Apple Hardware Test on it as well...

Apparently, if the red LEDs stay on, the riser is buggered -- that's not the case here, though.
 
Well, I ran Apple Hardware Test, -- it said there was nothing wrong.

However, swapping the risers around, ASP reports that Riser B is now empty, so it looks like the riser is hosed.

Damn.
 
Wow, weirder and weirder.

I put all the 2 GBs on the 'good' riser, all the 1 GBs on the 'bad' riser.

Put both risers back in...

I now have 12 GBs...😕
 
But the dual-channel operation requires that the first slots on the risers be filled with the highest-capacity DIMMs...doesn't it? So it should be 2.2.1.1 on both risers.

I can't see that the DIMMs were improperly seated... they all locked in as they were supposed to...
 
spetznatz said:
But the dual-channel operation requires that the first slots on the risers be filled with the highest-capacity DIMMs...doesn't it? So it should be 2.2.1.1 on both risers.

I can't see that the DIMMs were improperly seated... they all locked in as they were supposed to...
Click to expand...
I've had instances where I thought the DIMM was properly seated, and they locked. They were located in the correct slots. But like this situation, weren't read. The lock was sort of stiff/tight, BTW. Not make me think they wouldn't have worked, but that turned out to be the case.

Re-seating did the trick. 😉 At least it was something simple, rather than a bad riser or DOA memory. 🙂
 
rylin said:
Take them out and spin them clockwise?
Now that's some serious voodoo! 😀
Click to expand...

You misread the sentence. He means swap the boards over, also worded as rotate the boards. If you haven't worked as an engineer you would not understand that term....which you clearly didn't.
 
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