6gb of RAM is now 4gb of RAM

[santabarbaramac]

I bought 2 2gb sticks of matched RAM for my 2.8ghz 8-core Mac Pro. When I finished the install About Mac said I had 6 gb. This was 5 weeks ago. I just checked About Mac and it said I have 4gb now.

I don't know when the RAM stopped being recognized as 2gb sticks but it is gone now. System Profiler says that I have four 1 gb sticks. Not true, not possible.

They are installed properly and as I said the RAM was there at one point. Any ideas?

 

[bigbird]

Did you put your new 2GB sticks in Riser A, slots 1 & 2 and your Apple RAM in Riser B slots 1 & 2? If not, do so. If so, swap the slots 1 & 2 RAM in each riser but don't move the RAM to a different riser. If that does nothing then run a memory hardware test.

 

[tugger]

I have 6GB installed (2x2GB OWC in riser A, 2x1GB OEM in riser B). The machine has recognized all 6GB since I added the OWC chips on day one, and continued to recognize all memory after the 10.5.2 update.

The only major change I've made to my 2008 MP operating environment since 10.5.2 was the EFI Firmware update earlier this week. Afterwards I had two startup hangs a day apart and one kernal panic in Firefox. I've never had a kernal panic before -- didn't even know what it looked like -- but the log showed some kind of memory problem. I did an SMC reset and the problems stopped. Unfortunately I did not check the memory configuration with System Profiler when all of this was happening.

After reading your post today I checked the memory in System Profiler and the machine showed only 2GB. All slots in riser A were listed as "empty." I did a PRAM reset but the machine still recognized only 2GB. I then shut down, removed riser A, pulled the chips and reinserted them, and reseated the riser card. The machine is now recognizing all 6GB and lists all chips correctly in the System Profiler.

I have no conclusion to draw from all of this other than maybe a flakey EFI Firmware update process. I'll re-check the memory occasionally and report any further problems.

 

[macz1]

I would also try to remove the new RAM restart, reinstall RAM and restart.
Check the position of the modules and if they fit correctly (you have to apply some pressure to insert them completely)

Bad memory isn't to exclude completely although it's unprobable if it worked before...

 

[yomibro]

I have a similar issue with my Mushkin memory that I recently purchased, at times the system would show the full 16GB of memory and once in a while it would only show 14GB instead (2GB modules showing as 1GB). I did noticed that when the system was showing 14GB one of my memory card risers had a RED LED light on, figure I changed the memory module and riser card locations around to see if it's a faulty hardware and surely enough the issue followed a particular module around so I did an RMA with Newegg.

Check and see if you have a RED LED light on one of the memory riser cards when the system detects only 4GB.

 

[matt321]

You might try installing only the RAM that came with your Mac Pro and try doing the firmware update again, then reinstalling the RAM that you purchased at OWC