So I get:

pciide0 at pci0 dev 0 function 1: Silicon Integrated System 5597/5598 IDE controller
pciide0: bus-master DMA support present
pciide0: primary channel configured to compatibility mode
wd0 at pciide0 channel 0 drive 0: <Maxtor 90843D4>
wd0: drive supports 16-sector pio transfers, lba addressing
wd0: 8047MB, 16351 cyl, 16 head, 63 sec, 512 bytes/sect x 16481808 sectors
wd0: 32-bits data port
wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 2
wd1 at pciide0 channel 0 drive 1: <Maxtor 90843D4>
wd1: drive supports 16-sector pio transfers, lba addressing
wd1: 8047MB, 16351 cyl, 16 head, 63 sec, 512 bytes/sect x 16481808 sectors
wd1: 32-bits data port
wd1: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 2
pciide0: primary channel interrupting at irq 14
pciide0: secondary channel configured to compatibility mode
atapibus0 at pciide0 channel 1
cd0 at atapibus0 drive 1: <EPO CD-ROM CR-844S, , Ver4.20> type 5 cdrom removable
cd0: 32-bits data port
cd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 2
pciide0: secondary channel interrupting at irq 15
wd0(pciide0:0:0): using PIO mode 4, Ultra-DMA mode 2 (using DMA data transfers)
wd1(pciide0:0:1): using PIO mode 4, Ultra-DMA mode 2 (using DMA data transfers)
cd0(pciide0:1:1): using PIO mode 4, Ultra-DMA mode 2 (using DMA data transfers)

Then:

boot device: wd0
root on wd0a dumps on wd0b
root file system type: ffs
pciide0:0:0: lost interrupt
        type: ata
        c_bcount: 2048
        c_skip: 0
pciide0:0:0: Bus-Master DMA error: missing interrupt, status=0x41
wd0a: DMA error writing fsbn 16 of 16-19 (wd0 bn 16; cn 0 tn 0 sn 16), retrying
pciide0:0:0: lost interrupt
        type: ata
        c_bcount: 2048
        c_skip: 0
pciide0:0:0: Bus-Master DMA error: missing interrupt, status=0x41
wd0: transfer error, downgrading to DMA mode 2
wd0(pciide0:0:0): using PIO mode 4, DMA mode 2 (using DMA data transfers)
wd1(pciide0:0:1): using PIO mode 4, Ultra-DMA mode 2 (using DMA data transfers)
wd0a: DMA error writing fsbn 16 of 16-19 (wd0 bn 16; cn 0 tn 0 sn 16), retrying
wd0: soft error (corrected)


After that it works correctly, but my disk light is always on :-)

christos