Dual Channel Ram Kit: to buy or not to buy?

There are a lot of posts about this in the forum. You might wanna try the SEARCH option. Anyway, I bought 2x2gb for my Macbook even though I would not be able to get 4 gigs out of it. I just wanted to ensure I got the most out of my macbook and get it to be the fastest.
So if your budget is a concern, I guess you can get 2GB and a 1GB and it will probably be as fast as anything else. But for the price difference, I did not want to think what if...? Also I wasn't going to do this upgrade twice, so I just went with 4gb.
Hope this helps, but like I said definitely do a search, a lot of people asked about this and there are good answers from a lot of people.

The memory you listed is 667Mhz, which is for the newer Santa Rosa MacBooks introduced in November 2007. Since you're running Tiger on your computer, it's obviously older than that. That being said, the RAM you've indicated SHOULD work in your computer at the slower speed of the Napa platform.

You may want to verify that by googling about it before you buy.

As for your plan to simply buy two of the same brand/spec sticks and put them in the computer, that will work just fine.

No, you do not need to buy a packaged pair of RAM modules in order to get parity. All you need are two modules of the same speed and size. It is never a good idea to mix brands of RAM, but it sounds like you're not planning on doing that.

After some more research, the 667Mhz RAM will work just fine in your machine (albeit at the lower speed of the Napa platform). You're good to go.

Hi oil_sands: I believe the RAM for all the generations and models of MacBooks, MacBook Pros, and Intel iMacs are the exact same spec. The same specs as you listed in your initial post. I have mixed size, and manufacturer in my MacBook Pro and my iMac, absolutely no issue with either.

Stedman

oil_sands wrote:
...My question is that do I need to buy these as a packaged pair to ensure dual channel mode, or can I buy two of the same sticks in individual packs...

Either way. I don't think there is anything different or special about a package of two sticks and two separate packages of the identical manufacturer and specs. They are not really "matched" in any special way other than being the same spec. Can you really get them cheaper when purchased individually? Usually the package is priced a little cheaper.

The dual-channel RAM pipeline is a feature of the computer's RAM controller thingy, not the RAM itself.

oil_sands wrote:
bdkjones: thanks for the heads up, and yes you're correct my macbook is first gen. Is there a specific RAM speed I should be looking for my older mac, or is all the latest (and generally cheapest) RAM rated at 667Mhz?

Check the link below for your MacBook's chipset datasheet. Interesting technical reading. Achieving "dual-channel symmetric" only requires matching memory sizes, but doesn't require that every last detail of the modules be the same. If there was something different, both would revert to the slowest module. Even without matching memory sizes, the memory controller was designed for "dual-channel" operation up to the size of the smaller module. Intel calls this "dual channel asymmetric". In any case, it doesn't necessarily operate both modules as one "double wide" unit. The description is a little bit unclear.

If you want to read it for yourself, the Intel 945GMA Express chipset datasheet (I think this is yours) is here:

http://download.intel.com/design/mobile/datashts/30921905.pdf

This is on page 337 (the description of dual channel symmetric):

Three memory channel organizations are supported:
• Single-channel (Single SO-DIMM per channel)
• Dual-channel symmetric (Single SO-DIMM per channel)
• Dual-channel asymmetric (Single SO-DIMM per channel)

Each channel has a 64-bit data interface and the frequencies supported are 400 MHz, 533 MHz and 667 MHz.

On page 338:

*10.2.3.1 Dual-channel Symmetric Mode*
This mode provides maximum performance on real applications. Addresses are pingponged between the channels, and the switch happens after each cache line (64-byte boundary). The channel selection address bit is controlled by DCC[10:9]. If a second request sits behind the first, and that request is to an address on the second channel, that request can be sent before data from the first request has returned. Due to this feature, some progress is made even during page conflict scenarios. If two consecutive cache lines are requested, both may be retrieved simultaneously, since they are guaranteed to be on opposite channels. _The drawback of Symmetric mode is that the system designer must populate both channels of memory so that they have equal capacity, but the technology and device width may vary from one channel to the other._

As far as I recall, all MacBooks to this date were spec'ed for PC2-5300 (DDR2-667) SODIMMs, from the 1st generation up to the current ones. I even tried using a combination of PC2-4200 (DDR2-533) and PC2-5300 memory in different sockets on my Santa Rosa MacBook. When I checked System Profiler, the report was that both were running as DDR2-533, which was in line with what I read in the Santa Rosa spec; apparently the Santa Rosa chipset only supports DDR2-533 and DDR2-667 (no DDR2-400). Using PC2-4200 (DDR2-533) or slower may work in your 1st gen MacBook, but if it does you're taking a performance hit.

bdkjones wrote:
After some more research, the 667Mhz RAM will work just fine in your machine (albeit at the lower speed of the Napa platform). You're good to go.

DDR2-667 (PC2-5300) is a supported speed of that platform. I don't believe that it downgrades the speed. Or at least that's the impression I got from reading the Intel 945GMA (Napa) datasheet.

If anything slower is used, it gets interesting. There was a small table of what happened with different combinations of memory speed (3 speeds supported) and graphics host speed (2 speeds supported) with the display and render clocks. In any case, it looks like using PC2-5300 (DDR2-667) would be best for overall performance.

Yep, YPW is right.

Santa Rosa and Napa share 667 DDR2 RAM. It's only the front side bus speed that was bumped for Santa Rosa. My mistake, sorry for the confusion!