Matrox G450 SDR vs DDR?

[WetWilly]

I've noticed G450 SDR cards popping up, but I haven't seen any reviews of their performance. It doesn't sound like the G450 handles SDR/DDR like the Geforce MX, i.e. 128-bit SDR/64-bit DDR, but rather the memory bus is permanently 64-bit. So,

1) Am I correct on the memory bus?
2) How much of a hit there is with SDR vs DDR on the G450?

Thanks in advance