Welcome to the MacNN Forums.

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > 3GB RAM in new iMac?

3GB RAM in new iMac?
Thread Tools
Paco Loco
Forum Regular
Join Date: Jun 2001
Location: London, UK
Status: Offline
Reply With Quote
Aug 9, 2007, 08:58 AM
 
Is it necessary to keep the same size RAM chips in both slots? e.g. put a new 2GB chip in the spare slot while retaining the supplied 1GB chip in the other?
Or is it best to stick to either 2 x 1GB or 2 x 2GB chips?
     
Andy8
Mac Elite
Join Date: Apr 2003
Location: Hong Kong
Status: Offline
Reply With Quote
Aug 9, 2007, 09:00 AM
 
1 + 2 = 3
     
Paco Loco  (op)
Forum Regular
Join Date: Jun 2001
Location: London, UK
Status: Offline
Reply With Quote
Aug 9, 2007, 09:07 AM
 
Anyone else got any helpful input?
     
P
Moderator
Join Date: Apr 2000
Location: Gothenburg, Sweden
Status: Offline
Reply With Quote
Aug 9, 2007, 09:58 AM
 
It is not necessary, the machine will boot with unmatched RAM. The advantage to having matched RAM is that the memory performance will go up slightly due to the ability to make 128-bit reads and writes (ie, read or write 128 bits in one cycle instead of two, which is what it takes otherwise). This only matters in operations that rely heavily on the memory subsystem, which is rather uncommon but does happen (eg video encoding). For machines with integrated video, it is more important as 128-bit reads are very useful for graphics operations, but your iMac has a discrete GPU and is not affected.
     
Paco Loco  (op)
Forum Regular
Join Date: Jun 2001
Location: London, UK
Status: Offline
Reply With Quote
Aug 9, 2007, 11:47 AM
 
Thanks P. I take it that in summary you are saying that 3GB (unmatched) is better than 2GB (matched) in this example.

Strange that the Apple Store doesn't offer this as an option, all they offer is 2GB for £90 extra, or 4GB for £540 extra - that's some jump!!
     
angelmb
Addicted to MacNN
Join Date: Oct 2001
Location: Automatic
Status: Offline
Reply With Quote
Aug 9, 2007, 03:19 PM
 
     
analogika
Posting Junkie
Join Date: Feb 2005
Location: 888500128
Status: Offline
Reply With Quote
Aug 9, 2007, 03:24 PM
 
Originally Posted by angelmb View Post
so I guess this image showing 3GB as matched is an errata… right?

OWC runs the Apple Store?
     
angelmb
Addicted to MacNN
Join Date: Oct 2001
Location: Automatic
Status: Offline
Reply With Quote
Aug 9, 2007, 04:47 PM
 
I was pointing towards the 2GB + 1GB matched or unmatched RAM feature.
     
analogika
Posting Junkie
Join Date: Feb 2005
Location: 888500128
Status: Offline
Reply With Quote
Aug 9, 2007, 06:07 PM
 
Oh.

I go to bed now.
     
mduell
Posting Junkie
Join Date: Oct 2005
Location: Houston, TX
Status: Offline
Reply With Quote
Aug 9, 2007, 06:21 PM
 
They probably mean same manufacturer/timings/etc when they say matched. You don't want that kit, since you already have 1GB. You just want the 2GB module.
     
Mediaman_12
Professional Poster
Join Date: Jan 2001
Location: Manchester,UK
Status: Offline
Reply With Quote
Aug 9, 2007, 06:29 PM
 
It makes next to no difference. The same was said about the old Intel iMac's, and I have never noticed a problem with 1.5GB (original 512mb+new 1GB) in mine.
On a related topic, do the new iMac's use the same DIMM's as the original Core Duo iMac's?
Thinking of upgrading, and weather to swap the 1GB Dimm from old to new?
     
angelmb
Addicted to MacNN
Join Date: Oct 2001
Location: Automatic
Status: Offline
Reply With Quote
Aug 10, 2007, 02:43 AM
 
Originally Posted by mduell View Post
They probably mean same manufacturer/timings/etc when they say matched. You don't want that kit, since you already have 1GB. You just want the 2GB module.
Thanks Mark, it was to show you indeed can have different RAM modules there.
     
Simon
Posting Junkie
Join Date: Nov 2000
Location: in front of my Mac
Status: Offline
Reply With Quote
Aug 10, 2007, 06:53 AM
 
Originally Posted by Paco Loco View Post
Thanks P. I take it that in summary you are saying that 3GB (unmatched) is better than 2GB (matched) in this example.
P explained it very nicely. 3 GB is certainly better than 2 GB if you experience pageouts due to a lack of available RAM at 2 GB. The tiny memory performance decrease you can measure with unmatched pairs on such a system will easily be outweighed by the performance increase you experience when your system doesn't have to page out to the disk. As soon as your 2 GB system pages out the first time you'll already have lost more than you ever will due to using unmatched pairs. In short: If you need more than 2 GB, get more. Even if it's unmatched.
     
mduell
Posting Junkie
Join Date: Oct 2005
Location: Houston, TX
Status: Offline
Reply With Quote
Aug 10, 2007, 08:48 PM
 
Originally Posted by Mediaman_12 View Post
On a related topic, do the new iMac's use the same DIMM's as the original Core Duo iMac's?
Thinking of upgrading, and weather to swap the 1GB Dimm from old to new?
All Intel Macs, except for the Mac Pro, take the same memory. Feel free to swap it around.
     
soonlar
Fresh-Faced Recruit
Join Date: Aug 2006
Location: Minnesota
Status: Offline
Reply With Quote
Aug 10, 2007, 08:55 PM
 
Originally Posted by P View Post
It is not necessary, the machine will boot with unmatched RAM. The advantage to having matched RAM is that the memory performance will go up slightly due to the ability to make 128-bit reads and writes (ie, read or write 128 bits in one cycle instead of two, which is what it takes otherwise). This only matters in operations that rely heavily on the memory subsystem, which is rather uncommon but does happen (eg video encoding). For machines with integrated video, it is more important as 128-bit reads are very useful for graphics operations, but your iMac has a discrete GPU and is not affected.
P, assuming I am running my applications plus OS under 2gb used memory, are you saying that having 3gb (1+2) will encounter a slight performance hit versus 4gb (2+2)?
iPhone 4gb
Mac Mini Core Duo 1.66ghz
iPod Mini Silver 4gb
<Looking to purchase the new 24" iMac 2.8ghz core2 extreme>
     
Simon
Posting Junkie
Join Date: Nov 2000
Location: in front of my Mac
Status: Offline
Reply With Quote
Aug 11, 2007, 03:58 AM
 
Originally Posted by soonlar View Post
P, assuming I am running my applications plus OS under 2gb used memory, are you saying that having 3gb (1+2) will encounter a slight performance hit versus 4gb (2+2)?
4 GB matched is certainly better than 3 GB unmatched. OTOH having 3 GB unmatched is still better than having 2 GB matched and suffering from pageouts.
     
P
Moderator
Join Date: Apr 2000
Location: Gothenburg, Sweden
Status: Offline
Reply With Quote
Aug 12, 2007, 07:49 AM
 
Originally Posted by soonlar View Post
P, assuming I am running my applications plus OS under 2gb used memory, are you saying that having 3gb (1+2) will encounter a slight performance hit versus 4gb (2+2)?
Theoretically, if memory bandwidth is your bottleneck. It is very unlikely that it will happen that way in practice though, and if it does, you will not see a halving of performance on those operations. The bottleneck would move from the RAM interface (667 MT@64 bit) to the FSB (800 MT@64 bit).

Also, to reach symmetric dual-channel (ie, 128 bit reads), the two memory DIMMs have to be identical in more ways than just the same size - there has to the same number of identically sized chips on each DIMM, and possibly a few other things I don't remember at the moment. For the desktop Core 2 models it can make more of a difference, since the FSB is much faster, but even there it is mostly theoretical.

Unless you know for a fact that you are limited by memory bandwidth, just ignore the dual channel idea and load up with RAM as you would. If you are really concerned about memory bandwidth, get a matched 2x2 set to put the machine at 4 gig and sell the old 1 on eBay - or consider a Mac Pro. Memory bandwidth is the one area where they still provide a big performance advantage.
     
hsl
Dedicated MacNNer
Join Date: Jun 2001
Location: the netherlands
Status: Offline
Reply With Quote
Aug 12, 2007, 12:18 PM
 
strange that the new iMac has a FSB that runs 800Mhz and that the ram modules are 667Mhz, 800Mhz modules would probably be a bit faster...

But to react on the original question, no you don;t have to put ram in pairs, Apple also gives the option to put in 3GB and standard they put 1 1GB module in the machine.
15,4" MBP (late 2008), 2,53Ghz, 4GB RAM, 256GB SSD | 27" ACD | 11" MBA, 1.6Ghz, 4GB RAM , 128GB | 16GB iPhone4 | 32GB iPad

The biggest fan of JoliOriginals MacBook, iPad and iPhone Sleeves!
     
mduell
Posting Junkie
Join Date: Oct 2005
Location: Houston, TX
Status: Offline
Reply With Quote
Aug 12, 2007, 12:33 PM
 
Originally Posted by hsl View Post
strange that the new iMac has a FSB that runs 800Mhz and that the ram modules are 667Mhz, 800Mhz modules would probably be a bit faster...
Not strange at all; that's what the mobile chipsets from Intel support. 800Mhz RAM won't be any faster, since the chipset will run it at 667Mhz.
     
hsl
Dedicated MacNNer
Join Date: Jun 2001
Location: the netherlands
Status: Offline
Reply With Quote
Aug 12, 2007, 12:40 PM
 
ah ok, that is new for me, thx!
15,4" MBP (late 2008), 2,53Ghz, 4GB RAM, 256GB SSD | 27" ACD | 11" MBA, 1.6Ghz, 4GB RAM , 128GB | 16GB iPhone4 | 32GB iPad

The biggest fan of JoliOriginals MacBook, iPad and iPhone Sleeves!
     
Simon
Posting Junkie
Join Date: Nov 2000
Location: in front of my Mac
Status: Offline
Reply With Quote
Aug 12, 2007, 04:06 PM
 
Originally Posted by hsl View Post
strange that the new iMac has a FSB that runs 800Mhz and that the ram modules are 667Mhz, 800Mhz modules would probably be a bit faster...
That's only strange if you think of the FSB as the bus between CPU and RAM. But in Intel's design it's not. The "processor interface bus" connects the CPU with the Northbridge which in turn is connected to memory through the memory bus. The FSB can and actually does run at other speeds than the memory bus itself. In the iMac or MBP for example the FSB runs at 800 MHz while the Northbridge communicates at 667 MHz with memory. You can use 800 MHz DIMMs, but the Northbridge will still communicate at 667 MHz with the modules. This is also the reason why you won't get a performance increase with faster clocked memory.
     
hsl
Dedicated MacNNer
Join Date: Jun 2001
Location: the netherlands
Status: Offline
Reply With Quote
Aug 12, 2007, 05:14 PM
 
thx for the explanation now i don't have to worry i have to buy some new 2GB modules later when there are 800Mhz's available
15,4" MBP (late 2008), 2,53Ghz, 4GB RAM, 256GB SSD | 27" ACD | 11" MBA, 1.6Ghz, 4GB RAM , 128GB | 16GB iPhone4 | 32GB iPad

The biggest fan of JoliOriginals MacBook, iPad and iPhone Sleeves!
     
Pao|o
Dedicated MacNNer
Join Date: Jun 2003
Status: Offline
Reply With Quote
Aug 18, 2007, 09:00 AM
 
iMac Intel (Mid 2007) and Mac mini (mid 2007) Memory Testing of 1.0GB, 2.0GB, 3.0GB and "4.0GB*" configurations with timed tests using Photoshop CS3, a "Stress Test" (CS3 + iTunes Visualizer), "RAM Hog" (CS3 w/50% ram used by other things), Halo and XBench. See the note/disclaimer there on 4GB in the Mini (only 3GB accessable so the only benefit with that system of having 2x2GB modules is a very small gain from enabling dual-channel memory mode.)
     
mrpeepers
Fresh-Faced Recruit
Join Date: Aug 2007
Status: Offline
Reply With Quote
Aug 19, 2007, 10:42 PM
 
so if you going to recommend a place to purchase RAM for the new iMac would it be here?
Apple iMac Memory upgrades for 17", 20", & 24" Intel Core 2 Duo 1.83GHz 2.0GHz 2.16GHz 2.33GHz 2.4GHz and Core 2 Duo 'Extreme' 2.8GHz at OtherWorldComputing.com

If not, where do you all recommend for purchasing RAM for the iMac? I visited the Apple Store and it's like $500 for 2gb - WOW! Then again, I already have one but was considering adding 2 more.

And is there a brand here that I should stay away from?
Apple iMac Memory upgrades for 17", 20", & 24" Intel Core 2 Duo 1.83GHz 2.0GHz 2.16GHz 2.33GHz 2.4GHz and Core 2 Duo 'Extreme' 2.8GHz at OtherWorldComputing.com

Or rather, is the a brand you would recommend?
     
P
Moderator
Join Date: Apr 2000
Location: Gothenburg, Sweden
Status: Offline
Reply With Quote
Aug 20, 2007, 05:26 AM
 
I'd go with a brand, that's the most important thing. Kingston, Crucial and Corsair have all been good to me - Kingston is the one I've used the most, ever since the Performa days - but make sure that wherever you're getting it has a decent return policy and is big enough not likely to fold in the next few weeks.
     
mrpeepers
Fresh-Faced Recruit
Join Date: Aug 2007
Status: Offline
Reply With Quote
Aug 20, 2007, 09:54 AM
 
where do you buy yours from? Newegg? I was thinking about Newegg too...
     
mrpeepers
Fresh-Faced Recruit
Join Date: Aug 2007
Status: Offline
Reply With Quote
Aug 20, 2007, 10:39 PM
 
anyone?
     
mduell
Posting Junkie
Join Date: Oct 2005
Location: Houston, TX
Status: Offline
Reply With Quote
Aug 20, 2007, 11:58 PM
 
Newegg loves you.
     
mrpeepers
Fresh-Faced Recruit
Join Date: Aug 2007
Status: Offline
Reply With Quote
Aug 21, 2007, 10:30 AM
 
so here:

Newegg.com - Buy Computer Parts, PC Components, Laptop Computers, Digital Cameras and more!

I had Patriot in my windows computer - and it ran beautifully... I may go with it again. Any other suggestions?
     
mduell
Posting Junkie
Join Date: Oct 2005
Location: Houston, TX
Status: Offline
Reply With Quote
Aug 21, 2007, 07:05 PM
 
Crucial from Newegg
     
glideslope
Grizzled Veteran
Join Date: Mar 2002
Location: NY
Status: Offline
Reply With Quote
Aug 21, 2007, 08:45 PM
 
Crucial in all are Macs. Always. I purchase direct from Crucial.
To know your Enemy, you must become your Enemy.”
Sun Tzu
     
bembol
Junior Member
Join Date: Apr 2005
Location: gta|brampton
Status: Offline
Reply With Quote
Aug 22, 2007, 12:51 AM
 
I only trust Kingston. I picked up a 2GB today for $160 CAN (taxes-in). I'm running 3GB not in a rush to run 4GB.
     
bbales
Mac Elite
Join Date: Jan 2003
Location: suburban Chicago
Status: Offline
Reply With Quote
Aug 22, 2007, 09:17 AM
 
I bought the 2GB from Other World. I haven't installed it yet, however, so I have no idea if I"ll have trouble or not. I'm not anticipating any, however.
     
   
Thread Tools
 
Forum Links
Forum Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Top
Privacy Policy
All times are GMT -4. The time now is 09:05 PM.
All contents of these forums © 1995-2017 MacNN. All rights reserved.
Branding + Design: www.gesamtbild.com
vBulletin v.3.8.8 © 2000-2017, Jelsoft Enterprises Ltd.,