Correct, all three-figure models are at least DDR3. The X20x support up to 8 GB (2x 4 GB).

Edit: And no, they really don't support more. The memory controller only supports 2 Gb chips, so with two ranks per channel you only get 2x 4 GB. (Intel i7-600, i5-500 series processor datasheet, section 2.1.1).

The datasheets are often outdated. See http://www.businesswire.com/news/home/20100923006778/en/Sams... for an example.

Yes, such things are often outdated, but the availability of different memory chips does not change existing hardware. The MC really doesn't support it, there is no way to change anything about that...

I believe there were other chips at the time that supported more than 8 GB (i7-9xxM perhaps), but these are a different die (Clarksdale quad cores, ie. high end mobile chips that are selected desktop chips).

And if you read http://www.intel.com/content/www/us/en/processors/core/core-... , it does not say anything about 4Gbit DDR3 either.

The difference is that with the one DS we know it's accurate because anything beyond 2 Gb simply doesn't work. So that DS is accurate. On the other hand we know that with Clarksdale more than 2 Gb does, in fact, work, just like they work on Lynnfield. As one would expect, it's the same silicon after all.

If you'd excuse me now, I believe my work here is done ;)

And here is another example (notice it almost works, proving there is no hardware limitation): http://apple.stackexchange.com/questions/42426/can-i-upgrade...

The point is that the datasheet is now inaccurate. This happened before with 2Gbit DDR3 and Intel had to update the datasheet for the Mobile 4 Series chipsets.

The datasheet says that the IMC only supports 2 Gb chips, which remains accurate. Even a single 8 GB DDR3 module will not work with these laptops.

Correct, had too many machines on the bench this week.