The memory modules used for this model are SDRAMs (Single Data Rate). A glance at the inscription "TC50" reveals that the best access time is 5.0 nanoseconds. That means that the card could potentially be overclocked to 200 MHz. The version available in stores, however, will only be furnished with 5.5-nanosecond memory, which means that most of the overclockers will have to make do with 180 MHz.
You can tell that memory and chip clocks both run at 175 MHz in the new powerstrip version. You have to alter settings on both regulators at the same time.