I honestly can't remember about such details, but with IDE drives and 95A you were limited to PIO. You could enable DMA in 95B, it wasn't by default. It was in W98. That should make a drastic difference.
I wrote about this in PC Pro in about 1995-1996. Because it had a true pre-emptive kernel, it could do other stuff while waiting for disk I/O, and on NT, enabling DMA made a big difference. As I recall, on 98, it just made disk access a bit quicker, that was all.