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Mr. Anderson

Moderator emeritus
Original poster
Nov 1, 2001
22,568
6
VA
Online BTO options for PowerMacs have both options availble. What's the difference and why are there options here when the price is significantly different.

D
 

slooksterPSV

macrumors 68040
Apr 17, 2004
3,543
305
Nowheresville
Mr. Anderson said:
Online BTO options for PowerMacs have both options availble. What's the difference and why are there options here when the price is significantly different.

D
ECC - Error Correction ram. - I'd use this if I was doing sensitive work. What it means is if there is a parity in the RAM then it'll fix it. Servers use this kind of RAM same with scientists and a lot of others.

Non-ECC means it won't correct parity's on its own. You just have to flush the RAM (restart) or redo what you were doing to remove the parity.

Parity-checking RAM detects single bit errors.

One bit throws off a byte, one byte off everything

http://www.scl.ameslab.gov/Projects/old/ClusterCookbook/memory.html
 

ipacmm

macrumors 65816
Jun 17, 2003
1,304
0
Cincinnati, OH
ECC RAM (error correcting code) is normally used on a server motherboard for more reliability and costs more, the extra 8 Bits is used to correct the data passing through. Your motherboard probably cannot use ECC RAM and if it able to use ECC RAM it cannot be combined with NON ECC RAM. ECC is parity RAM, Non-ECC RAM is Non-parity RAM. Most types of RAM come in either NON ECC or ECC.

I ordered my Power Mac with non-ecc 1GB...I might switch to ECC ram later, my windows server takes ECC ram. I can't really tell any difference.
 

slooksterPSV

macrumors 68040
Apr 17, 2004
3,543
305
Nowheresville
ipacmm said:
I ordered my Power Mac with non-ecc 1GB...I might switch to ECC ram later, my windows server takes ECC ram. I can't really tell any difference.
Well you won't really. If you've had a kernel crash or that, there could have been a parity in the RAM. On PC's they won't load up if there is a parity stuck in the RAM. So things just die basically. That's why some vendors RAM works better than others, because they have a fake parity checking mechanism on the RAM.
 

Mr. Anderson

Moderator emeritus
Original poster
Nov 1, 2001
22,568
6
VA
Hmmm, interesting - so this is basically so things don't crash? How about doing 3D animation - even though its computationally top heavy, its not doing continuous calculations, just trying to determine pixel colors for each rendered image.

D
 

Skareb

macrumors member
Oct 24, 2005
88
0
Adelaide
Mr. Anderson said:
Hmmm, interesting - so this is basically so things don't crash?
n_3wokq6bk.jpg

ECC chip is the chip in the centre of the ram stick

ddr2-samples.jpg

Obvioulsy not present in the Non-ECC RAM

ECC RAM is more or less a waste of time (unless you're running a server or chomp through CAD programs allday. It actually slows done RAM access times as all the data is checked for errors.

Keep in mind that up until now Apple hasn't supproted ECC RAM and life has been fine.

My advice, save your pocket and increase your speed by buying Non-ECC.

Cheers
Jordan

P.S: Indepth writeups can be found on http://www.aandtech.com, http://www.tomshardware.com etc...
 

Makosuke

macrumors 604
Aug 15, 2001
6,667
1,250
The Cool Part of CA, USA
I agree that, unless you're doing something super-sensitive, it's probably not worth it; it will eventually save you from an app (or OS) crash, but only VERY rarely, so it's probably not worth the added expense and slightly slower RAM for most folks.

To give a positive example, OSX's server monitor loggs errors that were caught and corrected by EEC RAM. I have an XServe with EEC RAM running at work, and in the past 6 months of 24X7 fileserver use, it has caught and fixed exactly one error.

Now, that error could've brought down the entire server, so it was worth it in this case (and there will probably be another a few months from now), but for a home computer I doubt you'll ever notice.

The 3D rendering is an interesting example of somewhere it *might* be useful; if you're running renderings that take days, it would suck terribly to have it crash near the end, and since RAM speed probably doesn't make that much difference (processor bound, after all), EEC might be a worthwhile investment since you're probably spending heaps on hardware anyway.
 

big_malk

macrumors 6502a
Aug 7, 2005
557
1
Scotland
To give a positive example, OSX's server monitor loggs errors that were caught and corrected by EEC RAM. I have an XServe with EEC RAM running at work, and in the past 6 months of 24X7 fileserver use, it has caught and fixed exactly one error.

Are these errors logged in non-server OS X? I am curious if I have ever been saved a crash by it.
 
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