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The new iMacs are the same configuration as the MacBook Pro Santa Rosa -- that is, they will recognize up to 4 Gb (2 x 2 Gb SODIMMs) and they use the same DDR2-667 SODIMMs.

The new Mini Core2Duo however uses the same chipset as the MacBook -- meaning DDR2-667 SODIMMs, but officially only supporting 2 Gb (2 x 1 Gb) although it's reasonable to suspect that after testing, a 3 Gb configuration ( 1 Gb + 2 Gb) could be used.
 

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According to the Apple store:

"Your iMac uses one of the fastest memory technologies available today — 667MHz, Double Data Rate (DDR2), synchronous dynamic random-access memory (SDRAM) — ensuring that the dual-core processor is constantly fed with data without wasting clock cycles."
Sure sounds like SDRAM and not SODIMM to me.
 

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Now that we've answered the same question 3 times correctly, is there a bonus round? ;)
 

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Discussion Starter · #8 ·
This is kinda confusing. I'm running an Intel iMac and the "About this Mac" pane indicates that my RAM is SDRAM. I'm hoping to hang on to the 1GB RAM module I bought and installed last summer so I can toss it into my next iMac, which I won't be getting until Apple releases 10.5.
 

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(( p g )),

You will be fine with putting the same stick of RAM that you're using in your current Intel iMac into your future, released yesterday, iMac. They do use RAM of same size and speed.
 

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SDRAM = Synchronous Dynamic Random Access Memory.

All PC666/100/133, DDR and DDR2 RAM is synchronous, so it is all SDRAM. The old SIMMs and DIMMs in classic 68000/020/030/040 Macs were non-synchronous.

An informal convention has cropped up to refer to the earlier non-DDR RAM as SDRAM and to consider DDR RAM as not-SDRAM but that is not accurate.

DIMM (dual inline memory module) SODIMM (small outline DIMM) and MicroDIMM refer to the physical layout of the module, irrespective of it's electrical characteristics or timing.

DDR (Double Data Rate), DDR2 (and soon DDR3) refer to the electrical standards of the RAM and the way the module deals with the memory bus timing clock - double refers to the fact that these modules can perform 2 operations in one tick of the clock.

533 and 667 refer to the speed of the RAM in MHz -- this is directly related to the other numbers you will see, which describe the nominal bandwidth of the RAM

400 MHz = 3200 DDR400 = PC3200 DDR2400=PC2-3200
533 MHz = 4200 DDR2-533 = PC2-4200
667 MHz = 5300 DDR2-667 = PC2-5300
800 MHz = 6400 DDR2-800 = PC2-6400

There is potential confusion in the crossover speed area between DDR and DDR2, so I try to call DDR RAM by the PC3200 naming, and DDR2 RAM by the DDR2-400 naming.
 

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Does this hold true for the first gen intel iMacs?
All CoreXXX intel Macs use the same DDR2-667 SODIMMs.
The different versions of Mac do have different maximum capacities.
CoreDuo and CoreSolo machines max out at 2 Gb (2 x 1 Gb)
Core2Duo machines (presumably including the new C2D Mini) can use 2 Gb SODIMMs, with a limit of 3.3 Gb, so practically, 1 x 1 Gb + 1 x 2 Gb is the max.
Core2Duo SantaRosa and Core2Extreme machines can use a full 4 Gb RAM ( 2 x 2 gb SODIMMs)
 

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All CoreXXX intel Macs use the same DDR2-667 SODIMMs.
Core2Duo SantaRosa and Core2Extreme machines can use a full 4 Gb RAM ( 2 x 2 gb SODIMMs)
Thanks for the info. Can the new 4 Gb RAM systems use 3 Gb? I'm thinking of picking up a new one with 1 gig and buying another 2 gigs from you. Right now I'm trying to get my buddy to buy my old iMac with 1 or 2 gigs in it.
 

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Thanks for the info. Can the new 4 Gb RAM systems use 3 Gb? I'm thinking of picking up a new one with 1 gig and buying another 2 gigs from you. Right now I'm trying to get my buddy to buy my old iMac with 1 or 2 gigs in it.
The Santa Rosa MBP and new iMac can support a 3 Gb configuration -- you'll give up maybe 6% real world speed, relative to the matched pair 4 Gb configuration because the 3 Gb configuration won't have Dual Channel access. It should still be faster than a 2 Gb machine, if you are using any heavy programs at all.
 

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Thanks for the info. Can the new 4 Gb RAM systems use 3 Gb?
Yes. iMacs do not require equal paired RAM DIMM's, nor do they benefit from having them installed as so.
 

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Yes. iMacs do not require equal paired RAM DIMM's, nor do they benefit from having them installed as so.
That's not accurate. All intel Macs benefit from dual-channel access with matched RAM.

If you were to say that the benefit is small because the iMacs have their own dedicated VRAM and don't take as much of a performance hit on mismatched RAM as compared to the MacBook and Mini, then that would be on target.
 
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