"Assuming 33MHz system bus speed" is refering to the speed of the PCI bus, not the DMA modes your hardware may support. PIO stands for "programmed I/O". If you are interested in what these are just do a search on "programmed I/O". Newer hard drives use DMA modes now by default not PIO modes. The message you see isn't saying your hard drive is not using DMA. If your hard drive was /dev/hda you can see if DMA is enabled with:
This must be run as root. Look at the manpage for hdparm for more info.