Hard Drive Speed

I recently went to PcPitStop.com and ran a test for my hard drive and it came back that the Cached Speed is running at about 53% slower than other related systems and I don’t know why. I have DMA checked and I regularly defrag my system. It was noted that Cached speed has to do with memory and processor but my memory was running at 97% so it’s not that ( I don’t think ). Any ideas?? This system works pretty slow. It is a AMD 800 with over 400mb of ram. The hard drive is 27 Gigs broken up into 6volumes running ata 66. Thank you for your help!!