Mac Pro Wont See Ram!

The answer depends on whether you have the early 2008 Mac Pro or the original.

If you have the new early 2008 Mac Pro you have to place all the 1GB modules in one riser and the 2x4GB or 2x2GB modules in the other (sorry, have a hard time seeing if you mean 4GB in total as in 2x2GB or 8GB as in 2x4GB).

I have the same problem and apparently two of my slots are faulty on one memory riser.
I am going to have to get the riser replaced.

HarryJoaquin said:

Iv just got an extra 4GB of ram for a MacPro 8-core (2x4GB chips on top of the standard 4x1GB chips) I can get 6GB to work but 2 wont show up.

Click to expand...

Hi,

Have you check OWC guides yet? They're quite helpful:
http://eshop.macsales.com/Customize...=install_videos/macpro/macpro_quicksheet.html

And here are their installation videos: http://eshop.macsales.com/tech_center/installation.cfm

I had more or less same issue with RAM I've bought for MP. I had to remove and reseat new modules several times, before they get recognised. That's pretty common on MP.

sash

Never had a problem with my Mac Pro (1,1).

In the top riser, I have 2x512MB sticks, and on the bottom riser, I have 2x1GB sticks. Both sets are different brands (however they're both the same 667MHz).

But I know that sometimes re-seating the modules, or swapping the ports can help the MP recognize them. Also, make sure that they're in the order of the modules. For example, don't fill up slot #4 if you have nothing in slots 1, 2, and 3. They're labeled by little numbers (so get your eyeglasses).

Did you mean 2x2 instead of 2x4?

If so, did you put the 2x2 on the top riser and the 4x1 on the bottom?

I have 8 Gigs of ram installed in 4 2gig chips. I was having the same problem, but through research and trial, I figured it out.

This is how they need to be installed for optimal performance. (I use this naming system, because it is very clearly printed the same way on the DIMM riser cards.)

PCB-A
DIMM1----(set a)2GB
DIMM2----(set c)
DIMM3----(set b)2GB
DIMM4----(set d)

PCB-B
DIMM1----(set a)2GB
DIMM2----(set c)
DIMM3----(set b)2GB
DIMM4----(set d)

If you want to install more ram, it needs to be in sets of two. The next one to install into, obviously, would be DIMM slot 2 (labeled set c)

Does that help?

The risers also have a hardware check built in. Look for a little red led next to each memory slot on the risers. This will tell you if something hardware related is going on.

dilbert4life said:

I have 8 Gigs of ram installed in 4 2gig chips. I was having the same problem, but through research and trial, I figured it out.

This is how they need to be installed for optimal performance. (I use this naming system, because it is very clearly printed the same way on the DIMM riser cards.)

PCB-A
DIMM1----(set a)2GB
DIMM2----(set c)
DIMM3----(set b)2GB
DIMM4----(set d)

PCB-B
DIMM1----(set a)2GB
DIMM2----(set c)
DIMM3----(set b)2GB
DIMM4----(set d)

If you want to install more ram, it needs to be in sets of two. The next one to install into, obviously, would be DIMM slot 2 (labeled set c)

Does that help?

Click to expand...

Ram in the mac pro is probably the most misinterpreted piece of info.


If you want to add memory, yes it needs to be in pairs.
If youre upgraded any model, for example the current 8core to add additional memory it should be:

RISER CARD A (Top Riser)
Slot1 - 1GB
Slot2- 1GB
Slot3 - Empty
Slot4 - Empty

RISER CARD B (Lower Riser)
Slot1 - 2GB
Slot2 - 2GB
Slot3- Empty
Slot4- Empty

then youd fill RISER CARD A with memory in slot 3 & 4 of RISER A, then to top it if is to fill slots 3&4 of RISER B


make sure OP, you have the 800Mhz FB-DIMMS for your 2008 MacPro.
If not then its causing conflict, use the memory installation as just outlined above.

if there are no RED LED light son your memory riser when its in use then its either not installed properly or pair wrong.