TOMS有解釋9800用的ddr2:

The memory now runs 10 MHz faster, at 350 MHz (DDR II). In practice, however, the clock increase is irrelevant because the DDR II memory has a higher latency time compared to DDR modules. It's interesting, though, that the Samsung memory modules used on the test card are specified for up to 450 MHz. When asked about this, ATI explained that they were able to buy these modules at a good price from Samsung after one of their larger clients cancelled. When the cards hit the retails stores, they should also be equipped with these memory modules. Overclockers will be pleased. The heat, however, increases from hot to sizzling, as shown by the first overclocking tests. Perhaps this is also the reason why ATI doesn't simply bring higher-clocked versions of these cards to the market.