lost my memory

Question

I have a early 2008 Mac Pro dual quad 2.8 and used to have 10 gb of memory, but after updgrading to OS 10.8 I noticed I have only 6 gb of memory, so I checked the About This Mac and found that all the DIMM A slots show "empty".  So I pulled the riser 820-2178-B and bought another one, flipped in the memory, and voila!  same story: 6 Gb of memory.  What else can be wrong?Thanks!

Allan Eckert · Accepted Answer

RAM does go bad. It does not have an infinite life expectancy. Allan

johnnyVDO · Answer

Yeah, but 4 GB of ram went kablooie all at once? And all on the DIMM A side?  The riser is okay, and I flip flopped the "bad" ram to the good side and it did indeed seem to be dead.

The hatter · Answer

using 8 DIMMs improves bandwidth 17%these are high quality 667&#x27;s (small 4% drop) and they are also which is very important, run much much cooler than what they use to make - my run 48 to 64*CNew OS always seems to use and change how memory is managed mapped and used and &#x27;finds&#x27; what was marginal. fbdimms die a death from all the heat and stress by hot/cold cycles. use to be needed to use smcfancontrol - a must - to cool them better to get more air down in the memory cageHow To Install and Remove Memory Mac Prohttps://support.apple.com/kb/HT44332x2GB FBDIMM DDR2 667MHz @ $29http://www.amazon.com/BUFFERED-PC2-5300-FB-DIMM-APPLE-Memory/dp/B002ORUUAC/

johnnyVDO · Answer

Can I install these on the DIMM A side (4x2gb) and will the computer recognize the other 6 GB of 800MHz memory that is already installed?  Thanks!Memory Slots:  ECC:          EnabledDIMM Riser B/DIMM 1:  Size:          1 GB  Type:          DDR2 FB-DIMM  Speed:          800 MHz  Status:          OK  Manufacturer:          0x802C  Part Number:          0x3948544631323837324A5938304545314434  Serial Number:          0xE22796CCDIMM Riser B/DIMM 2:  Size:          1 GB  Type:          DDR2 FB-DIMM  Speed:          800 MHz  Status:          OK  Manufacturer:          0x802C  Part Number:          0x3948544631323837324A5938304545314434  Serial Number:          0xE227955ADIMM Riser A/DIMM 1:  Size:          Empty  Type:          Empty  Speed:          Empty  Status:          Empty  Manufacturer:          Empty  Part Number:          Empty  Serial Number:          EmptyDIMM Riser A/DIMM 2:  Size:          Empty  Type:          Empty  Speed:          Empty  Status:          Empty  Manufacturer:          Empty  Part Number:          Empty  Serial Number:          EmptyDIMM Riser B/DIMM 3:  Size:          2 GB  Type:          DDR2 FB-DIMM  Speed:          800 MHz  Status:          OK  Manufacturer:          0x802C  Part Number:          0x3138484632353637324A4438304545314434  Serial Number:          0xE13C2BE6DIMM Riser B/DIMM 4:  Size:          2 GB  Type:          DDR2 FB-DIMM  Speed:          800 MHz  Status:          OK  Manufacturer:          0x802C  Part Number:          0x3138484632353637324A4438304545314434  Serial Number:          0xE13C2BE0DIMM Riser A/DIMM 3:  Size:          Empty  Type:          Empty  Speed:          Empty  Status:          Empty  Manufacturer:          Empty  Part Number:          Empty  Serial Number:          EmptyDIMM Riser A/DIMM 4:  Size:          Empty  Type:          Empty  Speed:          Empty  Status:          Empty  Manufacturer:          Empty  Part Number:          Empty  Serial Number:          Empty

Grant Bennet-Alder · Answer

Those FBDIMMs work in pairs, so if either module fails, they both drop out.Your Mac Pro 65lb tower features Error Correcting Code memory. Modules working badly can be detected immediately, and are either mapped out (as you have seen) or cause the machine to halt on a machine-check to avoid contaminating your data.

hipzip2002 · Answer

thank you!