I'm getting around 100 MB/s for the write speed. I'm on Sata II and AHCI is not supported by this board (Asus P5N-D). Considering the SATA II and lack of AHCI, is this what I should be seeing in terms of write speeds, or should it be higher?
If memory serves, then you are pretty much on the mark. We've had several other posts about older LGA 775 motherboards with similar lack of capabilities. Time to start thinking about a new motherboard.