Yes, that's all it does. It's only enabling DMA (as it is called in windooz). But be sure you'r harddisk and/or motherboard is supporting this otherwise your server won't work and probably will hang or crash when you finish setup and want to reboot.
This is what happend to mee when I enabled this option on a board that didn't support DMA. E-smith wanted to restart but hang at the hdparm section which is the DMA support.
Timothée