Bank 0/DIMM0 or Bank 1/DIMM!?? Which is master/slave??

2GB and 512MB are the sizes of the DIMMs, not the speed. You can insert them in either bank. You only see a speed benefit if both DIMMs are the same size (i.e., you have 2 DIMMs that are both 2GB).

slave / master has to do with hard drive configurations, has nothing to do with ram.

as posted above, doesn't matter what slot the ram is in when using both slots.

I thought the "speed benefit" with using DIMMs of matched size came because it permitted dual channel transfers. According to the Crucial website, iMac's (mid-2007) NEVER operate dual channel. Why would the size match/mismatch make any difference to speed if that's the case?

LearningAlongtheWay wrote:

According to the Crucial website, iMac's (mid-2007) NEVER operate dual channel.

If that's what Crucial intended to convey, they're just plain wrong;
however, I believe their advice is just poorly worded and they meant
that iMacs don't require dual channel memory. (Some machines do.)

Apple clearly states that matched memory modules will yield improved
performance:

+"... when both SO-DIMMs are the same size and type, the interleaving+
+function is able to improve performance."+

[RAM Expansion Developer Note -- iMac|http://developer.apple.com/documentation/HardwareDrivers/Conceptual/HWTech RAM/Articles/RAM_implementation.html#//apple_ref/doc/uid/TP40003899-SW71200331177]

Looby

This is what the Crucial website says:

Maximum Memory: 4096MB
USB Support: 2.x Compliant
Standard Memory: 1024MB removable
Slots: 2 (2 banks of 1)
...
Q: Does my computer support dual-channel memory?
A: No.
Your system does not support dual channel.
Q: Does my computer support ECC memory?
A: No.
Your system does not support ECC. Because ECC and non-ECC modules should not be mixed within a system, install the same type of modules that are already in your system.
***
It would be helpful if Apple would put its own advice somewhere more readily accessible to regular computer users who want to upgrade their memory, like, say ... the iMac Manual.

The Crucial site is incorrect, the Apple technical documentation is correct. All Intel-based Macs support dual-channel.