Memory recognition

Hi! Since this is my first post, I'll introduce myself.

I work at a pro audio dealer here in MA. We have a few Macs that are used to demo software. I finally switched to a Mac after some time, myself

I've got an issue with one of our Mac Pros. It had 2GB (four 512MB sticks) in there, so I thought I'd upgrade and see how much it can improve. I got a 4GB kit (2GB sticks) and something strange happened when I installed them...

When I installed all 6GB (2GB in DIMM 1, 512MB in DIMM 2 and 3 on each card), only 2.5GB showed up. The first and third DIMM of card A showed up (the first 2GB and second 512MB), but nothing else.

I tried switching things around a bit, and installed the four 512MB in DIMM 1 and 2 of each card, then the 2GB in each card. This configuration showed the four 512MB sticks, but not the 2GB sticks.

I've tried other various combinations, but none have resulted in all 6GB being read.

I ran the hardware test and that showed what I saw under System Profiler.

Has anyone ran into this before? If so, what have you done to correct it?

Thanks a ton and I look forward to keep reading great tips and stories around here!

Yeah, I had a similar problems with my memory upgrade (4x 2Gb, 2x 1Gb). The big capactities go on the top slot, smaller on the bottom - in my case, yours may be different...

Have a look at the manual and all will be clear and you'll have 6Gb showing up.

Can I assume by your description...that you have a 2009 "Quad-Core" Mac Pro with 4 ram slots?

Are you absolutely positive that you purchased the correct ram?

It should meet these specs:

- Apple Specified Thermal Sensor
- DDR3 PC8500 ECC 1066MHZ
- 72 Bit (64 bit + 8 bit ECC)
- High-Performance Multi-Channel

Here's a link to more info:

Mac Pro Memory - Apple Mac Pro Xeon 8-Core and Quad Core Memory Upgrades DDR2 Fully Buffered 240 Pin DIMM 800MHz PC6400 / 667MHz PC5300

Hope this helps,

- Nick

If you're absolutely sure that you have the correct memory...then check out this video on how to install the memory in the 2009 Mac Pro's:

Mac Pro (2009) Memory (High Quality) Installation Video at OtherWorldComputing.com

Check out the last 25% of the video...it shows how a dialog box comes up if the new memory wasn't installed properly for best performance. Did you get any sort of dialog box such as this on restart?

- Nick

Wow, awesome quick responses! Thanks!

Sorry about that, I should have put the specs:

Dual-Core Intel Xeon 2.66GHz running 10.5.5. It is indeed not a 2009 model. The RAM I purchased for it reads the same as the RAM installed (other than capacity) - DDR2 PC2-5300

It's the kind that has the removable cards for the RAM, as opposed to putting the sticks right on the mother board.

I thought that the larger sticks had to go in the first slots, so I tried that first and that's when I noticed things didn't add up. After that, I tried different combinations.

For example: with the two 2GB installed on the first DIMM, riser B was not found. With all four 512MB sticks installed, all four are found. However, when I tried two 512MB sticks, each in DIMM 1 on each riser, only riser A was found.

AudioP said:

Wow, awesome quick responses! Thanks!

Sorry about that, I should have put the specs:

Dual-Core Intel Xeon 2.66GHz running 10.5.5. It is indeed not a 2009 model. The RAM I purchased for it reads the same as the RAM installed (other than capacity) - DDR2 PC2-5300

It's the kind that has the removable cards for the RAM, as opposed to putting the sticks right on the mother board.

I thought that the larger sticks had to go in the first slots, so I tried that first and that's when I noticed things didn't add up. After that, I tried different combinations.

For example: with the two 2GB installed on the first DIMM, riser B was not found. With all four 512MB sticks installed, all four are found. However, when I tried two 512MB sticks, each in DIMM 1 on each riser, only riser A was found.

Click to expand...

That info helps identify what computer you have...but your computer is most likely not a "dual-core, it's probably a "quad-core" 2.66 ghz Mac Pro from 2006.

Apple Mac Pro "Quad Core" 2.66 (Original) Specs (Mac Pro - MA356LL/A) @ EveryMac.com

On the inside of the side panel you have to remove from the Mac Pro, there is a stenciled graphic that explains how the memory must be installed. If this order is not followed properly...sounds like problems like you're experiencing can occur.

Here's a video as well on how to install the memory on a older Mac Pro.

Mac Pro (Pre-2008) Memory (High Quality) Installation Video at OtherWorldComputing.com

Hope this helps,

- Nick

Nick, thanks so much for that link. You were correct, it is a Quad Core. I couldn't find the etching where I always thought it was on the inside. I found it near the PCI slots.

I guess I was under the impression that each DIMM had to match on each riser. Oh how I was terribly wrong.

Thanks again for the help!

AudioP said:

Nick, thanks so much for that link. You were correct, it is a Quad Core. I couldn't find the etching where I always thought it was on the inside. I found it near the PCI slots.

I guess I was under the impression that each DIMM had to match on each riser. Oh how I was terribly wrong.

Thanks again for the help!

Click to expand...

The video I linked showed the stenciled graphic on the panel you remove. On my "quad-core" Mac Pro from 2006...the graphic is also on the panel. Maybe this "graphic" appears in various places.

In any case...please post your results...so that we know what your final outcome is.

Thanks,

- Nick

No sweat...

I left the four 512MB sticks in there just as they were installed... two in riser A, DIMMs 1&2 and two in riser B, DIMMs 1&2.

I was under the impression that I whatever I put in riser A would have to go in riser B. Meaning, if I put a 2GB stick in riser A, DIMM 3, a 2GB stick would have to go into riser B DIMM 3. Dual DIMM, it's called?

Not so much. I installed the two 2GB sticks into DIMMs 3&4 on riser A and left DIMMs 3&4 empty on riser B.

Viola!

Also, on this particular model, the specs were etched into the chassis under the vid card. It's always the last place you look...

AudioP said:

No sweat...

I left the four 512MB sticks in there just as they were installed... two in riser A, DIMMs 1&2 and two in riser B, DIMMs 1&2.

I was under the impression that I whatever I put in riser A would have to go in riser B. Meaning, if I put a 2GB stick in riser A, DIMM 3, a 2GB stick would have to go into riser B DIMM 3. Dual DIMM, it's called?

Not so much. I installed the two 2GB sticks into DIMMs 3&4 on riser A and left DIMMs 3&4 empty on riser B.

Viola!

Also, on this particular model, the specs were etched into the chassis under the vid card. It's always the last place you look...

Click to expand...

This sounds like things went successfully!!!

So what is your final ram total after the installation...5 or 6 gig?

Congrats again,

- Nick

Hi, I had similar problems on my MacPro 2.1 2x3Ghz QuadCore when I upgraded to 13GB. System Profiler now recognizes all DIMMs correctly, but Activity Monitor and the top command in the terminal only show 4G available.

Any idea what this could cause? I am running 10.6.1 snow leopard with a 32bit kernel. But as far as I know I should still be able to use/address more than 4 gig of RAM.

My hardware overview in system profiler:

Model Name: Mac Pro
Model Identifier: MacPro2,1
Processor Name: Quad-Core Intel Xeon
Processor Speed: 3 GHz
Number Of Processors: 2
Total Number Of Cores: 8
L2 Cache (per processor): 8 MB
Memory: 13 GB
Bus Speed: 1.33 GHz
Boot ROM Version: MP21.007F.B08
SMC Version (system): 1.15f3
Serial Number (system): 3T8050060Q0
Hardware UUID: 00000000-0000-1000-8000-001D4F459D98

Click to expand...

This is my RAM configuration:


And this is what it looks like in activity monitor:

I have exactly this problem Drago, with the same machine. Did you ever solve it? Thanks

OP post the 'About this Mac' pane so we know what model it is. My friend Nick is a little confused when he states 2006 Mac Pros are Quads - they are dual Xeon 5100 series CPU's unless they have been upgraded by X5355 which will then make it a Quad Core.

However memory is very touchy on Mac Pros. Did you get the low density memory from a Mac supplier, as high density PC memory will cause problems similar to what you are experiencing. Next question reading your thread is a little confusing. Are the modules fitted in matched pairs? This means Dimm Riser A positions one and two must have matched pairs as set out in Drago's post. Dimm Riser B then must have matched pair in positions one and two, Dimm Riser A must have matched pair in positions 3 and 4, BUT THEY NEED NOT BE IDENTICAL TO POSITIONS ! & 2.

All of this is set out in the user manual. If you did not get a manual, they are downloadable from the Apple Manuals web site.

manuals.info.apple.com/en/Mac_Pro_User_Guide.pd

@Harry:

I thought the memory modules used by the Pro series had to be ECC? Am I wrong or did I mistakenly read something out of context?

Correct Charlie DDR2 ECC ~ here is the precise specs:-


OWC 53FB1MPK02GB 2.0GB Mac Pro Memory Matched Pair... in stock at OWC

Being Dual Channel must be in matched pairs. Later Mac Pros did not call for matched pairs or heat sinks as the earlier models did.