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Old Jul 27, 2010, 08:51 AM   #1
Crunch
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Exclamation DDR3-1066MHz vs. DDR3-1333MHz RAM?

I've had my 21.5" for 2 1/2 weeks and now I want to upgrade. It's the higher-end one with the ATI 4650 HD card and the 1TB drive. Do I have a shot? I just passed the 14-day return window. I definitely want to upgrade to either the new 21.5" higher-end one or, for an extra $200, go with the lower-end 27"...

By the way, FYI, I have 16GB of DDR3-1066 RAM. Some of you may have added RAM as well so I checked that out as well: ALL four models with ALL of its base and upgradable processors support BOTH 1066MHz and 1333MHz DDR3 RAM.

How much of a difference between the two speeds will be noticeable? I could just sell all four of my 4GB DDR3-1066 chips (all NEW! Grrr...) and then buy DDR3-1333's...What a pain...

Any recommendations?
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Old Jul 27, 2010, 08:54 AM   #2
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The only difference between the two is maximum memory bandwith:

hypothetically, dual channel 1333mhz ram has 21gb/s memory bandwidth compared to dual channel's 1066mzh, which is rated at 17gb/s memory bandwidth. Only a select few tasks will take advantage of that amount of memory bandwidth, and the difference probably won't be significantly noticeable.
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Old Jul 27, 2010, 10:53 AM   #3
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1333MHz has higher latency, but again its not noticeable.
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Old Jul 27, 2010, 11:54 AM   #4
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By the way, does the CPU always dictate as to what type of RAM must go into whatever computer, or is it a combination of the chipset and the CPU?
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Last edited by Crunch; Jul 28, 2010 at 06:11 AM.
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Old Aug 11, 2010, 09:57 AM   #5
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DDR3-1066MHz vs. DDR3-1333MHz RAM for non-experts.

Gentlemen,

You guys seem pretty smart on this. I just bought my first iMac (21.5" 3.06...). It has 4GB of RAM and I wanted to upgrade it by adding 8GB more. Of course after I order 8GB of PC3-8500 (1066mhz) RAM, I realized that the iMac I have has 1333mhz installed. Will adding the 8GB of 1066mhz RAM increase the speed of my machine or slow it down? I don't use it for anything intense like gaming, just photo and video processing. Is it worth adding the extra 8GB if its 1066mhz? Thanks for the help.
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Old Aug 11, 2010, 10:15 AM   #6
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Originally Posted by volunteer1995 View Post
Gentlemen,

You guys seem pretty smart on this. I just bought my first iMac (21.5" 3.06...). It has 4GB of RAM and I wanted to upgrade it by adding 8GB more. Of course after I order 8GB of PC3-8500 (1066mhz) RAM, I realized that the iMac I have has 1333mhz installed. Will adding the 8GB of 1066mhz RAM increase the speed of my machine or slow it down? I don't use it for anything intense like gaming, just photo and video processing. Is it worth adding the extra 8GB if its 1066mhz? Thanks for the help.
For speed and reliability, all RAM should be of the same type.
If you put in 1066MHz RAM (and your machine expects 1333MHz), one of two things will happen. Either all the RAM will slow to match the slowest module in the machine, or you'll have system crashes related to the mismatched RAM.

I don't think there's much of a price difference; stick with what Apple specifies for your machine. Check out Crucial.com - they have an online configurator... just tell it which Mac you have and it'll show you only the compatible memory choices.
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Old Aug 11, 2010, 10:35 AM   #7
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Make sure you get the RAM for your machine.

2010 iMac: PC-10600 (1333Mhz)
2009 iMac: PC-8500 (1066Mhz)

If you install PC-8500 in a 2010 iMac it will cause your current RAM to drop down to the same speed, it may even cause some performance issues or make the system crash at times.

The 2009 iMac does not support PC-10600 so it will (if it works at all) will drop down to PC-8500 speeds. On top of that PC-10600 is more expensive so its not worth even trying it.

The easiest way to make sure things run smoothly is to get all matching specs.
Different brands are ok (try to at least keep matched pairs).

2010 iMac: PC-10600 (1333Mhz) CL 9
2009 iMac: PC-8500 (1066Mhz) CL 7
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Old Aug 12, 2010, 04:06 AM   #8
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No, the correct answer is that it does not matter. You can mix RAM of both speeds (1066/1333). The system will automatically use the slower speed, but there is no risk of system crashes. And no, 1333MHz RAM will not be recognized in a 2009 iMac, but 1066MHz in the 2010 is just fine.
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Old Aug 12, 2010, 04:08 AM   #9
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Quote:
Originally Posted by Crunch View Post
And no, 1333MHz RAM will not be recognized in a 2009 iMac, but 1066MHz in the 2010 is just fine.
You can use 1333MHz in 2009 i5 and i7 iMac
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Old Aug 12, 2010, 04:27 AM   #10
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You can use 1333MHz in 2009 i5 and i7 iMac
as long as you replace the already present 1066Mhz RAM with 1333Mhz. Otherwise the 1333Mhz sticks will be degraded to 1066Mhz as well.
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Old Aug 12, 2010, 05:56 PM   #11
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You can use 1333MHz in 2009 i5 and i7 iMac
I stand corrected. That's right. Looking at the 2009 models a little closer, you can also use 1333MHz RAM with the Core 2 Duo 3.33GHz, which is an upgrade option on all non-quad models.
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Old Aug 22, 2010, 08:25 PM   #12
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Exclamation Apple tech support says you can not put 1333MHz in a 2009 MP running at 1066.

Has anyone actually (or know of someone) who tried to but 1333 memory 3 x 4GB or 4 x 4GB in a 2009 MP (mine is a One 2.66GHz Quad-Core Intel Xeon "Nehalem" processor). Reading this thread, it seems that no damage will occur and it either won't run or it will run at minimum 1066 clock speed??????

I was able to get 2 kits Corsair XMS3, DDR3, 1333MHz 4GB X 4 (16BG total) 9-9-9-24 1.5V UNBUFFERED, 240PIN, NON-ECC, SDRAM (# CMX8GX3M2A1333C9) at FRYs for $200 each but I do not want to open the package unless I get firm opinion that it will work.

My logic at this price: I can hold on to the memory for my next MP running the same 1333MHz memory. HELP, I only have 2 weeks to return the memory!!!

Last edited by joefee; Aug 23, 2010 at 01:40 PM. Reason: additional info
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Old Aug 23, 2010, 07:07 PM   #13
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Called Corsair and they, like apple tech support do not recommend non-ecc modules.
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Old Aug 23, 2010, 09:51 PM   #14
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I was able to get 2 kits Corsair XMS3, DDR3, 1333MHz 4GB X 4 (16BG total) 9-9-9-24 1.5V UNBUFFERED, 240PIN, NON-ECC, SDRAM (# CMX8GX3M2A1333C9) at FRYs for $200 each but I do not want to open the package unless I get firm opinion that it will work.
First, this thread is asbout iMacs--NOT Mac Pros.

Second, if your machine supports ECC, then for the love of the spaghetti monster, GET ECC MEMORY!!! ECC = Error Correcting Code. That is, if the RAM ever messes up, the computer will know it, and instead of crashing or corrupting your data, it will fix it.
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Old Mar 24, 2011, 04:25 PM   #15
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This is old now... but I just did this today... works fine... it downclocks your RAM to 1066... otherwise no ill effects... my computer is a ******** faster though at loading.
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Old May 31, 2011, 01:07 AM   #16
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Originally Posted by MrXiro View Post
This is old now... but I just did this today... works fine... it downclocks your RAM to 1066... otherwise no ill effects... my computer is a ******** faster though at loading.
Interesting you have faster load time ... that's probably the latency.

1066Mhz DDR3 so dimms that are Mac compatible MUST be class 7 low latency

all 1333Mhz so dimms that I have seem are much slower latency CLass 9 but they will run the faster latency (Class 7) when clocked down to 1066.7 Mhz

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Old Jun 23, 2011, 10:22 AM   #17
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This is old now... but I just did this today... works fine... it downclocks your RAM to 1066... otherwise no ill effects... my computer is a ******** faster though at loading.
Get out. Really? Are you comparing 's to 's ?

You say you changed ONLY the RAM in the SAME machine that takes 1333MHz? What computer did you do this on?
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