THE ORIGINAL DDR memory was specified at 266MHz throughput and ended up at 400MHz officialy, with vendors like OCZ or Corsair going up to 600MHz in selected parts. Now, the DDR2 official spec is frozen at 800MHz, but there are plenty of parts running at 1066MHz and above for 'enthusiasts'. Now, in the famous press kit that Nvidia sent to the journalists on the Nforce 680i a month ago, for the first time, another new speed grade was mentioned - an 'upcoming version' of Corsair Dominator overclocker's memory, running at no less than PC9600, or DDR2-1200 throughput speed! And, there is even talk of extending the DDR2 spec to 1066MHz officially.
Realistically, you probably couldn't run that memory at this speed with anything less than 2.2 volts supply - far higher (and hotter) than the 1.8 volt specificiation of original DDR2 or the selected dies used on those DIMMs. In many cases, 2.3 volts are recommended, coming close to the old 2.5 volt DDR1 voltage levels. Are we going too far with DDR2, instead of early switching to the 1.5 volt DDR3 at the 1333MHz throughput?