I’ve a Black Macbook (Late 2006 A1181) which is supposed to have a limitation of 2GB Ram.  Browsing through the specs on my machine using MacTracker I see that although Apple state a 2GB limit, my machine will actually support 3GB Ram.  I was curious to see why 3GB would be the limit, surely if 1 Ram slot can support a 2GB SODIMM why can’t the other?  So I ordered 2 x 2GB Sticks from Crucial (CT25664AC667) and they worked just fine. 

I now have 4GB of RAM in my 2006 Macbook and it’s running perfectly, way faster than before.

I also checked MacTracker for the Memory options for my Early 2008 I-Mac (MB325LL/A) and that can apparently support 6GB of RAM as opposed to the 4 GB Apple specify as the maximum.  Back to Crucial and I ordered a single compatible 4GB Stick (CT51264AC800) and I now have 6GB Ram in my iMac.  At $90 each I didn’t want to try 2 x 4GB sticks just yet but I am tempted.

So both my Macs have had third party memory upgrades beyond the maximum capacity Apple specifies, and both are working great. 

I know both John & Dave successfully upped the Ram in their 2008 Macbook pros, but it seems to me that there’s a far wider range of Macs that could benefit from some extra RAM.  I’d suggest people check out the actual memory capacity of their Macs using MacTracker (free from AppStore) and see if you can’t breath some new life into your old kit.

I really don’t need to replace either of my Macs now as they’re both running much faster with far fewer page outs.

Mark.

I had the same success with my Graphite Clamshell iBook. The spec limit on RAM was (I think) 320MB, but I’ve run with 576MB for years with no issues. My understanding is that Apple always under-specs it’s machines, whether intentionally or not.

Enjoy!

Of further note, I just recently upgraded our early 2008 iMac to Lion. In order to do so I had to upgrade the RAM from the stock 1GB. According to Apple it maxes out at 4 GB, but according to MacTracker and OWC there is a 6GB limit. Talking with a Genius at the Apple store I was told that the problem with this is that the RAM in the two slots should be matched. I opted for the 4GB upgrade (2x2). OWC’s 6GB upgrade consists of 1 2GB and 1 4GB stick. Kingston does make a 3GB stick that would work in order to keep them matched, but I’m cheap and I was in a hurry.

Hi there,

On older Intel Macs, there is a limitation for the amount of system-addressable RAM.  While the OS reports 4 GB, only 3 will be used.

Some resources:

http://reviews.cnet.com/8301-13727_7-10327594-263.html?tag=mfiredir

http://www.everymac.com/systems/apple/macbook_pro/faq/macbook-pro-core-2-duo-3-gb-memory-limitation-details.html

Jason

I have 1x4gb + 1x2gb in my 2008 mbp for a total of 6gb (4gb official).

As I understand from the modest research (google) that I’ve done, the maximum limit of 6gb on mine for example is the most memory addressable - as to whether or not there can be problems from adding more (such as 2x4gb), that seems to be debated..

UPDATE: what the guy above said ^

I always wondered if Apple specked out systems with memory that was available when the system was in development. I’ve seen this for years; that Apple says PowerMac XXXX can only use 512Mb of RAM. It had 2 slots and 256MB DIMMS were all that were available. A year later 512MB chips come on the market but Apple never went back to retest old models. When my 2008 MacBook came out Apple said no more than 4Gb RAM. It has 2 slots and 2Gb chips were the largest I could find. I believe 4s and possibly 8’s are available now.

Not that I have any urge to go beyond the 4 that’s in there. I’m using it as an argument to get a new MacBook Pro.
“See Honey, Apple says the system can only take 4Gb but with all the Virtual Machines I run I need more like 8”

MacOCD - 17 January 2012 06:13 AM

I’ve a Black Macbook (Late 2006 A1181) which is supposed to have a limitation of 2GB Ram.  Browsing through the specs on my machine using MacTracker I see that although Apple state a 2GB limit, my machine will actually support 3GB Ram.  I was curious to see why 3GB would be the limit, surely if 1 Ram slot can support a 2GB SODIMM why can’t the other?  So I ordered 2 x 2GB Sticks from Crucial (CT25664AC667) and they worked just fine. 

I now have 4GB of RAM in my 2006 Macbook and it’s running perfectly, way faster than before.

I also checked MacTracker for the Memory options for my Early 2008 I-Mac (MB325LL/A) and that can apparently support 6GB of RAM as opposed to the 4 GB Apple specify as the maximum.  Back to Crucial and I ordered a single compatible 4GB Stick (CT51264AC800) and I now have 6GB Ram in my iMac.  At $90 each I didn’t want to try 2 x 4GB sticks just yet but I am tempted.

So both my Macs have had third party memory upgrades beyond the maximum capacity Apple specifies, and both are working great. 

I know both John & Dave successfully upped the Ram in their 2008 Macbook pros, but it seems to me that there’s a far wider range of Macs that could benefit from some extra RAM.  I’d suggest people check out the actual memory capacity of their Macs using MacTracker (free from AppStore) and see if you can’t breath some new life into your old kit.

I really don’t need to replace either of my Macs now as they’re both running much faster with far fewer page outs.

Mark.

I have a late 2006 MacBook Pro (v2,1) with 3GB of RAM. I never went to 4 GB because the chip and/or motherboard would not address more. This was a hard limit on the machine and adding more RAM would not make sense. I was actually told that if I installed 2 x 2GB chips that I would only be able to address 2GB and not 3 GB.

geoduck - 02 February 2012 11:05 AM

Not that I have any urge to go beyond the 4 that’s in there. I’m using it as an argument to get a new MacBook Pro.

Ahh, clever thinking. This may apply to my MBP as well…

Installing more memory than your operating system can address is one thing you need to consider when trying to exceed the recommended max. RAM.  However, even if the version of OS you are running can address more memory than the manufacturer’s maximum recommendation, there are also performance issues to consider.

One “trick” all computer manufacturers (including Apple) use to speed up system performance is memory interleaving (also known as “Banking”).  In memory interleaving the system will be set to perform accesses (reads/writes) to multiple DIMMs simultaneously.  This in effect multiplies the amount of data that can be read from/written to the DRAM per unit of time.  If your application routinely works with large amounts of information stored in sequential chunks of memory addresses, this can significantly improve the system performance as the CPU doesn’t have to stop and wait as often for data to be pulled from memory (DRAM is very slow compared to the processor speed). 

The limitation of interleaving is it requires DIMMs of the same capacity.  If you install DIMMs of unequal capacity, most systems will still work, but they will either not use the portion of the larger DIMM that doesn’t have a match in the smaller DIMM, or it will turn memory interleaving off, potentially significantly slowing down the system.  In the first event, your system reports it has more memory than it actually uses, in the 2nd event the system has more memory available, but pays a speed penalty.

Apple’s specs are probably geared to maintaining system performance so the customer base doesn’t come back and ask why installing more memory actually slowed the system down.

In reality,  If you don’t notice an appreciable slowdown by installing mismatched DIMMs and you are certain the system actually uses the extra memory (not just reports you have more), then go ahead.  If, on the other hand you notice your system is running appreciably slower with the unmatched DIMMs, then it’s time to decide what is more important to you, speed (with less total but interleaved memory) or total memory size.

Of course if you’re running applications that exceed the total amount of memory in the system then you will REALLY slow down (as the OS has to continually swap data between the DRAM and the hard drive (hard drives being significantly slower than even DRAM), also known as “thrashing the disk”).  If running with unmatched, non-interleaved DIMMs will increase the total available system memory enough to keep you away from “disk thrashing” then it will be a speed improvement for your situation.

Whatever you do, make sure you are getting a return on your investment and not just handing more money over to the memory manufacturers and/or slowing your system down to the point you’re unhappy.

I’ve had similar change in fortune. I’ve been able to keep an MBPro and iMac working longer with a 2GB increase in each to reach 6GB. I don’t think mine are matching pairs.
MBPro 2008  
Model Identifier: MacBookPro4,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.5 GHz

iMac 2008
Model Identifier: iMac8,1
Processor Name: Intel Core 2 Duo
Processor Speed: 3.06 GHz

A year or so ago, I did the same thing to my 2008 2.8 GHz Intel Core 2 Duo iMac, by installing the 4 + 2 kit from OWC, the first people to have it available, I believe. They said it was fully tested, etc., etc., but I don’t believe it made a damned bit of difference to the speed of my Mac.  I’ve even thought of going back to 2 + 2, since my Mac has been slowing down lately; ever since I “upgraded” to Lion, actually.  Although yesterday’s update to 10.7.3 seems to have made it a little faster.

These are the OWC specs, and I believe them to be a reliable company.

Product Specs:

OWC Memory fully meets Apple’s specifications with special attention to proper thermal specifications.

I’ve also considered the matched pairs issue, but I don’t feel like popping $90+ just to find out if another 4 GB stick might work.  Kind of fed up with the whole thing.  Speed sucks.  Lion sucks.  Three-year warranty has expired.

I’m running a Mac Pro Quad 2.66Ghz (Early 2009) with the Apple rated max of 16GB.
OWC does sell a 48GB kit but it costs: US$744 or a 32GB kit for US$497 both of which are still out of my price range.

Honestly with 16GB I can’t see the reason to add more RAM…..

(edited to fix a typo)

furbies - 02 February 2012 10:50 PM

I’m running a Mac Pro Quad 2.66Ghz (Early 2009) with the Apple rated max of 16GB.
OWC does sell a 48GB kit but it costs: US$744 or a 32GB kit for US$497 both of which are still out of my price range.

Honestly with 16GB I can’t see the reason to add more RAM…..

(edited to fix a typo)

HAH! I remember saying that about 16MB of RAM!