6 Replies Latest reply: May 1, 2015 4:15 AM by hipzip2002
johnnyVDO Level 1 Level 1 (125 points)

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!


OS X Mountain Lion (10.8.2), FCP 7
  • Allan Eckert Level 8 Level 8 (47,205 points)

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

     

    Allan

  • johnnyVDO Level 1 Level 1 (125 points)

    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 Level 9 Level 9 (60,800 points)

    using 8 DIMMs improves bandwidth 17%

     

    these are high quality 667'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*C

     

    New OS always seems to use and change how memory is managed mapped and used and 'finds' 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 cage

     

     

    How To Install and Remove Memory Mac Pro

    https://support.apple.com/kb/HT4433

     

  • johnnyVDO Level 1 Level 1 (125 points)

    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:          Enabled

     

    DIMM Riser B/DIMM 1:

     

      Size:          1 GB

      Type:          DDR2 FB-DIMM

      Speed:          800 MHz

      Status:          OK

      Manufacturer:          0x802C

      Part Number:          0x3948544631323837324A5938304545314434

      Serial Number:          0xE22796CC

     

    DIMM Riser B/DIMM 2:

     

      Size:          1 GB

      Type:          DDR2 FB-DIMM

      Speed:          800 MHz

      Status:          OK

      Manufacturer:          0x802C

      Part Number:          0x3948544631323837324A5938304545314434

      Serial Number:          0xE227955A

     

    DIMM Riser A/DIMM 1:

     

      Size:          Empty

      Type:          Empty

      Speed:          Empty

      Status:          Empty

      Manufacturer:          Empty

      Part Number:          Empty

      Serial Number:          Empty

     

    DIMM Riser A/DIMM 2:

     

      Size:          Empty

      Type:          Empty

      Speed:          Empty

      Status:          Empty

      Manufacturer:          Empty

      Part Number:          Empty

      Serial Number:          Empty

     

    DIMM Riser B/DIMM 3:

     

      Size:          2 GB

      Type:          DDR2 FB-DIMM

      Speed:          800 MHz

      Status:          OK

      Manufacturer:          0x802C

      Part Number:          0x3138484632353637324A4438304545314434

      Serial Number:          0xE13C2BE6

     

    DIMM Riser B/DIMM 4:

     

      Size:          2 GB

      Type:          DDR2 FB-DIMM

      Speed:          800 MHz

      Status:          OK

      Manufacturer:          0x802C

      Part Number:          0x3138484632353637324A4438304545314434

      Serial Number:          0xE13C2BE0

     

    DIMM Riser A/DIMM 3:

     

      Size:          Empty

      Type:          Empty

      Speed:          Empty

      Status:          Empty

      Manufacturer:          Empty

      Part Number:          Empty

      Serial Number:          Empty

     

    DIMM Riser A/DIMM 4:

     

      Size:          Empty

      Type:          Empty

      Speed:          Empty

      Status:          Empty

      Manufacturer:          Empty

      Part Number:          Empty

      Serial Number:          Empty

  • Grant Bennet-Alder Level 9 Level 9 (52,895 points)

    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 Level 1 Level 1 (0 points)

    thank you!