[loren s]

Like the 512 that comes with it, can that be removed to let me swap in two chips ? or is it sodded in the system ??

[Eug Wanker]

iMac G5 1.8/2.0 - Two accessible slots
iMac G5 1.9/2.1 with iSight - One accessible slot only <-- Stupid!
iMac Core Duo with iSight - Two accessible slots

[harrisjamieh]

The iMac g5 with iSight has 512 built in that cant be changed, so you can add up to 2 gigs using 1 2 gig stick

[mduell]

Originally Posted by Eug Wanker

iMac G5 1.8/2.0 - Two accessible slots
iMac G5 1.9/2.1 with iSight - One accessible slot only <-- Stupid!
iMac Core Duo with iSight - Two accessible slots

To be more complete:
iMac G5 1.8/2.0 - Two accessible DIMM ("desktop sized") slots
iMac G5 1.9/2.1 with iSight - One accessible DIMM ("desktop sized") slot only <-- Stupid!
iMac Core Duo with iSight - Two accessible SO-DIMM ("laptop sized") slots, supports dual channel

[Weezer]

so it comes with 2 accessible slots, one of which comes with a 512 already in it, so you have only 1 slot to add to? Is this the kind of ram that you are supposed to add in pairs, or could I leave the 512 in there, and add a 1 gig stick to the other empty slot?

[harrisjamieh]

Weezer, as long as you are refering to the Intel iMac, then yes, it comes with a 512 stick with an empty slot for 1 more stick. You have a few options:

1) Add a 512 mb or 1 gb stick into the empty slot - giving you a total of 1 gig/1.5 gig respectivly
2) remove the 512 stick that came in the imac, and replace it with a 1 gig stick, and then add another 1 gig stick or 512 stick to give a total of 1.5 gig/2.0 gig

If you add memory so you end up with either 2 x 512 sticks or 2 x 1 gig sticks, your intel imac will 'talk' to the ram much more quickly, hence improving performance even more. If you have a 512 stick and a 1 gig stick in, then this 'extra performance' will not be recognised.

[Weezer]

so could 1 gig actually be faster than 1.5 gigs?

edit: also, does anyone have experience with OWC brand RAM?

[harrisjamieh]

No 1 gig wont be faster than 1.5 gig, because 1.5 gig has 1.2 as much again as 1 gig, but if you decide on a total of 1 gig, then it should be 2 x 512s and not a single gig stick as the 2 x 512s will be faster

[Eug Wanker]

Originally Posted by mduell

To be more complete:
iMac G5 1.8/2.0 - Two accessible DIMM ("desktop sized") slots
iMac G5 1.9/2.1 with iSight - One accessible DIMM ("desktop sized") slot only <-- Stupid!
iMac Core Duo with iSight - Two accessible SO-DIMM ("laptop sized") slots, supports dual channel

The iMac G5 1.8/2.0 also supports dual-channel RAM configs.

I assume the same is true for the 1.9/2.1, but it would be pointless since the only dual-channel config would be if you had 1 GB RAM total.

Actually I hear that dual-channel support in the 1.8/2.0 also was fairly useless anyway in terms of real-world performance. Dunno about the Core Duo.

[Peter753]

I ordered an imac core duo with a 1 gig stick and bought another from crucial. Will it utilize the dual channel stuff?

[harrisjamieh]

Yes, because you will have 2 x 1 gig sticks. The dual channel thing works if you have 2 sticks of the same size installed

[Peter753]

Alright thanks. I thougth they might have to be identical in specificatoins other than size.

[harrisjamieh]

Well you should get the same speed RAM, thats DDR5300 if i am correct, which technically means its the same spec, but i think you were using the word specifications' as in manufacturer if i am correct.

[Peter753]

I was thinking CL# and stuff. I was just concerned they had to be identical identical to take advantage of that, in the same way you must add ram in parody in the G5 towers. Then again maybe they aren't so picky either.

[Weezer]

can anyone refer to me some benchmarks of how significant the RAM pairing is? Is it a big deal if I just add a 1 gig stick to the existing 512?

[Weezer]

well, after doing some research, two good resources:

http://forums.macrumors.com/showthread.php?t=173944

http://forums.macrumors.com/showthread.php?t=176466

any comments to these?

i've said it before and i'll say it again, runnign dual channel is of no benefit unless the memory of single channel memory is less than that of the system bus, it's 667/667MHz thus single channel saturates the fsb.

iMac's FSB is 667 MHz, which translates into 5.4 GB/sec bandwidth. Since iMac Core Duo and MacBook Pro use 667 MHz DDR2 SO-DIMM (5.4 GB/sec in single-channel and 10.7 GB/sec in dual-channel), there should be little or no memory bottleneck. One may wonder then, what (if any) dual-channel memory interface signifies. Here's what.
CPU is not the only consumer of memory. Other components such as GPU, hard disk, SuperDrive, USB and FireWire devices, can transfer information directly (without CPU) to and from memory.
When memory is running faster than other components, it can be fed to other components at their maximum bandwidth with minimal delay (or latency). With single-channel memory interface, subsequent data is prepared after data is sent to the CPU. With dual-channel, data read from two memory modules are prepared concurrently. As soon as data from the first module is transferred, subsequent data from second module can be fed immediately.
What these mean in real-world performance may not be all that significant. We are talking about 5 to 10% improvement (if at that), which is not very noticeable to most users. But when every little drop matters to you, every little seconds saved could be worthwhile.

[Simon]

Weezer, thanks for those links. Although I understand the benefit of having dual channel memory, I have yet to see a benchmark showing how any G5 or Intel Mac using 2x1GB performs better on everyday apps (iLife, iWork, PS, etc.) than the same Mac running with 1x2GB.

I believe it basically comes down to what your second quote mentions about memory bottlenecks.

Unless I see otherwise, I'd go for the single 1GB SO-DIMM anyday over the 2x512MB because it leaves one slot open for later upgrades. If you have 2x512MB you will have to throw a stick away as soon as you want to add more RAM.

[mavherzog]

Originally Posted by Eug Wanker

iMac G5 1.8/2.0 - Two accessible slots
iMac G5 1.9/2.1 with iSight - One accessible slot only <-- Stupid!
iMac Core Duo with iSight - Two accessible slots

It may be stupid...but the RevB G5 iMac's can have a max of 2.5GB where currently the new Core Duo's are maxed out at 2GB. (perhaps the Core Duo will accept 2GB modules once they are available...now THAT would be nice!)

[mduell]

Originally Posted by mavherzog

It may be stupid...but the RevB G5 iMac's can have a max of 2.5GB where currently the new Core Duo's are maxed out at 2GB. (perhaps the Core Duo will accept 2GB modules once they are available...now THAT would be nice!)

The chipset in the Intel Macs (945PM) supports 4GB RAM... all we're waiting for is 2GB PC2-5300 SO-DIMMs.

[mavherzog]

Originally Posted by mduell

The chipset in the Intel Macs (945PM) supports 4GB RAM... all we're waiting for is 2GB PC2-5300 SO-DIMMs.

I'm hoping to keep my 20" Intel iMac 3 years or so...So 2-2GB sodimms could definitely be in my future...

[Weezer]

that seems like overkill imo, youre gonna start hitting diminishing returns around 1.5 gigs

[ciparis]

Originally Posted by Weezer

that seems like overkill imo, youre gonna start hitting diminishing returns around 1.5 gigs

RAM is gobbled much more quickly in the Core Duo due to Rosetta use. 2GB could be restrictive for some users (I've run out of physical RAM already in my 2GB system a number of times, though the system handled it well without noticeable slowdown).

[ciparis]

Originally Posted by Weezer

well, after doing some research, two good resources:

http://forums.macrumors.com/showthread.php?t=173944

i've said it before and i'll say it again, runnign dual channel is of no benefit unless the memory of single channel memory is less than that of the system bus, it's 667/667MHz thus single channel saturates the fsb.

any comments to these?

That comment is actually correct. Memory uses a 128-bit bus if it's dual channel, while the CPU is 64, but if the speed is identical it's memory speed = 667*128/8 = 10.67 GB /sec theoretical, while the bus is limited to 667*64/8 = 5.33 GB/sec, the same as a single SO-DIMM at these speeds.

[mduell]

Correct, but completey neglects to mention that other devices/components can access RAM directly.

[loren s]

RATS! Ok so got the mac and got the ram yes one slot..
Sooo it looks like the other one could be replaced... is it soddered on ? I could open er up and place it in even unsoder it if it is aplicapledable...

[Weezer]

er did you actually read the thread?

[PBG4 User]

Originally Posted by loren s

aplicapledable...

This word sounds like something Sylvester the Cat would say.