12 gigs of ram possible?

jvdrummer182

macrumors regular
Original poster
Jun 18, 2010
120
2
USA
Will my 27" i7 iMac run with 12 gigs of ram? The computer came with 2 x 2 gb cards and I am looking to add 2 x 4 gb ram cards.
 
Feb 15, 2009
5,486
1
Boston, MA
According to Apple, the new iMac can support up to 16 GB of RAM, but I think you're going to have to run Snow Leopard in 64-bit mode for it to recognize all the RAM.
 

Sun Baked

macrumors G5
May 19, 2002
14,859
57
All depends on the number of bits the chipset uses for the address bus, even though people toss around 64-bit EFI and trot out other numbers.

If the chipset is 32-36 bits for the address bus it'll have a limit far lower than the OS, while the workstations are running somewhere around a 40-bit memory address.

Even though most Intel CPU can support 36-40 bits, the chipset might only allow 8-16GB of ram, so the bit support is far below what the CPU can handle.

Intel wants us to upgrade, so they are adding bits to memory support rather slowly to the chipsets.
 

Thermonuclear

macrumors 6502
May 23, 2009
362
21
FYI: The Intel Core i3 CPUs as used in the new iMacs are limited to 16 GB RAM as per the specifications on Intel's web site. That's 34 bits of physical addressing.

Sad to say, all of our modern computers would be far more powerful if only developers could get a grip on reducing software bloat. It was more than thirty years ago that I learned Unix on a Digital pdp-11/70 that had only 22 bits of addressing (4 MB core RAM). And there were always multiple users on the timeshared machine.
 

dexthageek

macrumors 6502
Dec 7, 2007
391
0
yeah it works fine. Just make sure you get the right ram for your machine. The 2009 and 2010 machines use different ram.

2009 - PC-8500 1066Mhz CL 7
2010 - PC-10600 1333Mhz CL 9
 

pommack

macrumors newbie
Feb 19, 2010
23
0
yeah it works fine. Just make sure you get the right ram for your machine. The 2009 and 2010 machines use different ram.

2009 - PC-8500 1066Mhz CL 7
2010 - PC-10600 1333Mhz CL 9

Any ideas does the new 1333Mhz memory work in 2009 models?
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.