Mac Pro RAM changing sizes within System Profiler

I have a Mac Pro 8-core 2007 model, bought it used from GainSaver.com, and immediately bought from (I believe) 18004memory.com eight 4GB RAM cards for it. They've worked fine since the beginning (the last 3 years). I have to admit I haven't checked system profiler for quite a while to confirm the RAM specs in the memory area because in the past it's consistently read correctly (8 slots each with a 4GB card totalling 32GB of RAM). Simple. Except for today... I checked system profiler and it now reads as two of the eight cards are 2GB instead of the expected 4GB, so now my total RAM reads as 28GB instead of the expected 32GB. Any ideas? I've heard about people swapping out cards into different slots when the RAM wasn't being recognized at all, but this is different. I've not seen any mention in the forums regarding changing numbers (or at least I wasn't putting in the proper search parameters to find those posts). Any help or explanation would be much appreciated.

System Profiler reads:
Memory Slots:

ECC: Enabled

DIMM Riser A/DIMM 1:

Size: 4 GB
Type: DDR2 FB-DIMM
Speed: 667 MHz
Status: OK
Manufacturer: 0x80AD
Part Number: 0x48594D5031353146373243503444332D5335
Serial Number: 0x52661404

DIMM Riser A/DIMM 2:

Size: 4 GB
Type: DDR2 FB-DIMM
Speed: 667 MHz
Status: OK
Manufacturer: 0x80AD
Part Number: 0x48594D5031353146373243503444332D5335
Serial Number: 0x00881618

DIMM Riser B/DIMM 1:

Size: 4 GB
Type: DDR2 FB-DIMM
Speed: 667 MHz
Status: OK
Manufacturer: 0x8551
Part Number: 0x47523244463447425834514D38303051434C
Serial Number: 0x00000000

DIMM Riser B/DIMM 2:

Size: 4 GB
Type: DDR2 FB-DIMM
Speed: 667 MHz
Status: OK
Manufacturer: 0x8551
Part Number: 0x47523244463447425834514D38303051434C
Serial Number: 0x00000000

DIMM Riser A/DIMM 3:

Size: 2 GB
Type: DDR2 FB-DIMM
Speed: 667 MHz
Status: OK
Manufacturer: 0x80AD
Part Number: 0x48594D5031353146373243503444332D5335
Serial Number: 0x52661202

DIMM Riser A/DIMM 4:

Size: 2 GB
Type: DDR2 FB-DIMM
Speed: 667 MHz
Status: OK
Manufacturer: 0x80AD
Part Number: 0x48594D5031353146373243503444332D5335
Serial Number: 0x0088160E

DIMM Riser B/DIMM 3:

Size: 4 GB
Type: DDR2 FB-DIMM
Speed: 667 MHz
Status: OK
Manufacturer: 0x8551
Part Number: 0x47523244463447425834514D38303051434C
Serial Number: 0x00000000

DIMM Riser B/DIMM 4:

Size: 4 GB
Type: DDR2 FB-DIMM
Speed: 667 MHz
Status: OK
Manufacturer: 0x8551
Part Number: 0x47523244463447425834514D38303051434C
Serial Number: 0x00000000

Mac Pro 8-core Xeon, Mac OS X (10.6.6)

Posted on Jan 16, 2011 11:29 AM

Reply
5 replies

May 12, 2011 12:35 PM in response to bvkoski

I've never heard of this either, but I did notice something interesting: you actually have memory from 2 different manufacturers installed in your system. One set of 4 has an ID of 0x8551 and the other 4 have an ID of 0x80AD. That doesn't add up if you bought them all at once from the same place.


Does anyone else have access to your tower who could have swapped memory? (I don't know if you're home or office based, but I used to manage a graphics team and when upgrading one system I would often replace memory modules right on down the line on all our towers...)

May 12, 2011 12:55 PM in response to bvkoski

it now reads as two of the eight cards are 2GB instead of the expected 4GB, so now my total RAM reads as 28GB instead of the expected 32GB. Any ideas? I've heard about people swapping out cards into different slots when the RAM wasn't being recognized at all, but this is different. I've not seen any mention in the forums regarding changing numbers (or at least I wasn't putting in the proper search parameters to find those posts). Any help or explanation would be much appreciated.


RAM reporting half or less than it should with FBDIMMs has become somewhat common.


Call it what you want, they are defective and can cause further trouble (writing bad data for one) so you need to pull them if you know which and get them RMA'd.


FBDIMMs run hot and using SmcFanControl 2.2.x is a good way to improve air flow and cooling properties to help insure components work properly (RAM, graphic cards) - and anytime you know you will be stressing resources just use higher fan profiles instead of the default or what you need for lite use. 850 rpm helps for lite use and can't hear the difference, 1000-1200 you begin to hear fans and get much better cooling. Above that to insure even under heavy work loads.


It is much easier to keep or prevent a system from getting too hot and keep it in cooler range than to wait for fans to kick in and then try to expel heat. Heat also remains and can build up during sleep, so running the fans @ 1500 rpm before shutting down or putting to sleep is a good idea.


Bad RAM is bad RAM though. I see this more often and common with 1-2 yr old FBDIMMs from a very popular vendor, but not from Kingston and Crucial. Vendors or resellers can have RAM from different sources and batches of course. They should also be warranted 100%.

May 13, 2011 6:21 AM in response to bvkoski

my macpro actually did the exact same thing


currently it has 16mb of matched ram in 8 2mb sticks.


when i switched to windows vista through bootcamp all was fine, but when i switched back to osx from windows vista i only had 14mb, 2 of the sticks were reporting as 1mb each.


i rebooted and all was fine.


i tried the exact same thing and the same happened.


strange behaviour. ive not had to use windows for a few months now and my mac has been showing the full 16mb ever since.

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Mac Pro RAM changing sizes within System Profiler

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