RAM suddenly not recognized on Mac Pro

[dnocuz]

Hello,

I have a 2008 Mac Pro 3.1 2 x 2.8 Quad Core running OSX 10.8.5 with 8 GB 800 MHz DDR2 FB-DIMM. Recently my system has been a little sluggish and to make a long story short, I realized that the system profiler was showing only 4GB of RAM instead of the 8GB of RAM that came with the computer when I originally bought it. The configuration is 2 x 2GB cards in riser A and 2 x 2GB cards in riser B. After doing some troubleshooting it seems as though the 2 RAM cards in riser B are the problem. The riser itself seems to be fine. I've run tests using Apple Hardware Test and Rember, both finding no problems - but both could not see the bad RAM to begin with. I'm just wondering why the RAM has all of the sudden stopped working. Is it something that can be fixed or does the RAM need to be replaced?

Thanks,

Dino

 

[MacVidCards]

Swap and switch to narrow it down.

Probably a single bad stick.

Things break, even electronics.

 

[dnocuz]

Swap and switch to narrow it down.

Probably a single bad stick.

Things break, even electronics.

I tried swapping the pair - no luck. I'll try swaping the single sticks.

 

[pastrychef]

On my old 3,1, it would stop recognizing RAM whenever I took out the daughter cards. I had to reseat them, boot up to see if RAM was recognized, and repeat if not. It would sometimes take dozens of attempts but once recognized, it would continue to work until I pulled out the daughter cards again.

 

[dnocuz]

Swap and switch to narrow it down.

Probably a single bad stick.

Things break, even electronics.

Yes, you're absolutely right. Through a bit of trial and error I figured out that one of my RAM sticks is bad. It's the only one that causes the riser's red light to come on. Since the RAM needs to be installed in pairs, the Mac Pro was only reading 2 of the 3 good sticks. Looks like I'll be buying more RAM.

Thanks.

D

 

[midniter]

This is what worked for me:-

Precautions:
Shut off power, pull the plug and all chords attached to the tower.
Use static gloves ( lolx no one does)

I originally had all 8 x 1GB Ram.
So making the total = 8GB. All 8GB showed up.

I purchased on Amazon in 2018. (2x 4GB)
A-Tech for Apple 8GB Kit 2X 4GB PC2-5300 667MHz Mac Pro MacPro2,1 MacPro1,1 Mid 2006 A1186 MA356LL/A Memory RAM

No I'm not promoting anyone. This is just what I bought.

Riser card 1
Slot1: 4GB
Slot2 : 4GB
Slot3: 1GB
Slot4: 1GB

Riser card 2
Slot1: 1GB
Slot2 : 1GB
Slot3: 1GB
Slot4: 1GB

So making the total = 14GB, but only 10GB showed up. I never bothered with it. lolx.

Now in 2019 I purchased 2x 4Gb again.
A-Tech for Apple 8GB Kit 2X 4GB PC2-5300 667MHz Mac Pro MacPro2,1 MacPro1,1 Mid 2006 A1186 MA356LL/A Memory RAM

Riser card 1
Slot1: 4GB
Slot2 : 4GB
Slot3: 1GB
Slot4: 1GB

Riser card 2
Slot1: 4GB
Slot2 : 4GB
Slot3: 1GB
Slot4: 1GB

So making the total = 20GB, and all ram showed up.

When it comes to PC desktops, I was told, the best practice is to put similar cards in 1/3 or 2/4 slots, but it seems Apple does not work that way.

Hope this helps someone.