I was just looking at an Exadata X2-2 ordering document and noticed that it included 144GB of RAM. The sales rep pointed at the Exadata X2-2 datasheet and showed the 96GB to 144GB memory expansion option. Based on my reading of Intel Xeon (Nehalam) memory configurations, as long as each channel has a single dual-ranked module, all the memory can run at full 1333MHz speed. (Update: as noted in the comments, this is unfortunately not the case in Exadata; with the expansion unit memory runs at 800MHz). It populates the normally-empty third socket for each memory bank with an additional memory module.
It isn’t particularly cheap: $6250 per database node at US list price, but is a performance booster that doesn’t have ongoing support costs either. For OLTP environments, I like to say cache is still king, and even for those of you with pure data warehouses, 50% more PGA space can help out your sorts too.
And yes, I realize this isn’t particularly new; according to Kerry Osborne’s blog it came out (but wasn’t officially announced per se) at the same time as the storage expansion racks in the summer