MX400 Cards: The Differences
Graphics boards based on the GeForce2 MX400 are shipped with different memory configurations, usually 32 or 64 MB Single Data Rate SDRAM. Basically, the GeForce2 MX family also supports DDR memory, but if DDR memory is actually used, then the memory interface is narrowed to 64-bit. This means that a board equipped with DDR memory will have exactly the same performance as a board with SDR memory. Since DDR memory is still more expensive than SDR chips, almost all manufacturers are staying with the SDR type.
nVIDIA is well aware of the fact that 128-bit DDR boards with GeForce2 MX could easily reach the performance level of a GeForce2 GTS or GeForce2 Pro with only a small amount of overclocking. Also, 'DDR' is used intentionally to act as a marketing catchword - of course only the GeForce2 GTS and Pro cards are truly enhanced by this technology.
There are several types of SDRAM available that differ in their cycle time. Gainward and PixelView equipped their boards with 4 and 4.5 ns chips, giving them much more potential for higher memory clock speeds. While you can overclock the PixelView board on your own, Gainward even offers an 'Enhanced Mode' that runs the board at much faster frequencies.