Slow Primary IDE Channel?

[Kool]

I'm just having problem with the Primary IDE Channel not performing at full speed. My Pio 108, NEC 3500 and Liteon 166s have no problem with writing (16x) & reading (16x) at full speed on the Secondary IDE Channel, but on the primary channel they're maxed out at 10X reading and 8x writing with device buffers fluctuating continuously from 10-90%.

I use the same IDE cable for both IDE channels, DMA was enable.
The HDD is on SATA so there are no conflicts with having anything else on that IDE channel. The motherboard is Intel D865PERL with Intel 865 chipset.

Could it be a defective channel? Anyone have a solution to this.
If it can't be solved then I'll have to buy a PCI IDE card to test it out.