PATA on a SATA system doing PIO not DMA

[Russell Coker <ide@coker.com.au>]

I have a Pentium-D machine with ICH7 chipset running the 64bit version of FC5 
that has one S-ATA disk and one P-ATA disk.  The S-ATA disk runs normally 
giving good performance while the P-ATA disk does about 1.5MB/s (PIO).

I have the drivers loaded in the initrd (can even have the root filesystem on 
the P-ATA disk).  The P-ATA disk in question ran at full speed on RHEL4 in a 
32bit Celeron machine and has run at full speed in a Pentium 4 machine 
running FC5.

Any ideas or suggestions for tests I should perform?  Below is the relevant 
section of dmesg output:

Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
ide0: I/O resource 0x1F0-0x1F7 not free.
ide0: ports already in use, skipping probe
Probing IDE interface ide1...
hdc: WDC WD3000JB-00KFA0, ATA DISK drive
hdd: BENQ DVD DD DW1640, ATAPI CD/DVD-ROM drive
ide1 at 0x170-0x177,0x376 on irq 15
hdc: max request size: 512KiB
hdc: 586072368 sectors (300069 MB) w/8192KiB Cache, CHS=36481/255/63
hdc: cache flushes supported
 hdc: hdc1 hdc2 hdc3
hdd: ATAPI 48X DVD-ROM DVD-R CD-R/RW drive, 2048kB Cache
Uniform CD-ROM driver Revision: 3.20
ide-floppy driver 0.99.newide