Help with RAM issue(s)

[GoCubsGo]

I turned my MacPro on and the LED blinked indicating a RAM issue. I removed the RAM riser cards and re-sat them and it worked for a bit. Months later the situation arose again. Re-seating the riser cards didn't work so I began re-seating the ram. I had 8 slots filled with 2 GB each before the issue arose. 4 are stock and 4 are from OWC and purchased back in 2009.

I finally got it to start after seating two stock modules and two from OWC. Interestingly enough though, when I see the memory in system preferences, two slots aren't showing as being used when there is very clearly RAM seated and I am using the MacPro right now to write this.

So my questions are, why wouldn't two modules show up?
If two slots are being used as shown could this be a riser issue? There are 4 LEDs on each riser and all 4 illuminate upon startup; however, the bottom riser isn't showing LEDs illuminated now whereas the top riser does show LEDs illuminated.

MacPro 2009 octo-core, running 10.11.6
Configuration currently, though the system info doesn't show the bottom riser has any RAM installed.
Top riser
DIM 1: stock ram
DIM 2: OWC ram

Bottom riser:
DIM 1: stock ram
DIM 2: OWC ram

 

[lowendlinux]

Swap the top and bottom riser ans see if your RAM shows up.

 

[bsbeamer]

What size are the OWC sticks?

 

[DeltaMac]

Which MacPro do you have? Octocore often refers to the 2008, which is a MacPro3,1
2009 would be MacPro4,1
This makes a difference for how memory is configured. The 2009 doesn't have RAM riser cards, for example. All slots are on the CPU card, and troubleshooting is a bit harder, compared to the 2008, which has interchangeable riser cards for the memory.

 

[lowendlinux]

Which MacPro do you have? Octocore often refers to the 2008, which is a MacPro3,1
2009 would be MacPro4,1
This makes a difference for how memory is configured. The 2009 doesn't have RAM riser cards, for example. All slots are on the CPU, and troubleshooting is a bit harder, compared to the 2008, which has interchangeable riser cards for the memory.

It's a 3,1 the picture says 800Mhz FBDIMM's

 

[GoCubsGo]

Which MacPro do you have? Octocore often refers to the 2008, which is a MacPro3,1
2009 would be MacPro4,1
This makes a difference for how memory is configured. The 2009 doesn't have RAM riser cards, for example. All slots are on the CPU card, and troubleshooting is a bit harder, compared to the 2008, which has interchangeable riser cards for the memory.

That is right, I spaced on the make/model. But to lowendlinux's recommendation, I will swap riser cards once I am done making some calls and see if that further diagnosis the issue. I didn't do that, but I found the ram does not appear to be bad.
[doublepost=1517266976][/doublepost]Okay, I swapped the top riser for the bottom and vice versa. Now the RAM shows only 4 GB on the bottom riser, or I assume the bottom is depicted by the left hand side.

I swapped the risers and left the top riser empty. I then put in a matched pair of OWC ram on the top and the mac wouldn't start. I took those out and put in the matched pair of the factory ram and while it did boot, I am only showing 4 GB when I should show 8 (2 DIMMs on top, 2 on the bottom).

I am pretty stumped.

 

[GoCubsGo]

As an extra precaution, I went ahead and tested all RAM using the top riser board only. As it stands, the top riser board will show 2 GB (2 DIMMs) ram each time with all 8 DIMMs. Is it mildly safe to maybe assume that one of my riser boards are bad? It doesn't appear to be on the MOBO side because the top riser registered memory when the bottom didn't and then swapped, the bottom registered RAM if I used the top riser.

I hope that isn't too confusing.

BTW I found this in my diagnostic log:
I turned my computer on for the first time today at that time.

Last Run: 1/30/18, 8:59 AM

Result: Failed

Failure Type: Memory

Memory Slot: 140683558157417/140683558157424

 

[lowendlinux]

They're pretty cheap on ebay..pick one up and give it a shot.

When I had my 1,1 at work the slots the riser fit into needed cleaned about every 60 days since it was sitting on the carpet maybe try some alcohol and q-tip in the slots.

 

[SamirPD]

I would test each pair of ram by itself to rule out any ram failures. Then I would try each of the combinations here to see if you can get a combination that will work with everything:
http://www.xlr8yourmac.com/tips/Mac_Pro_FBdimm_Pairing.html

Strange how it stopped working after working fine for so long, but I've seen stranger things happen.