It's some kind of timing problem, if I turn on more debuging (= longer
delays), the problem goes away. Is there any delay or timeout involved
in ide that can be increased?

This is the dmesg output, wdc0 is a NS 87312.

NetBSD 1.4.1 (ZEM) #1: Thu Sep  9 15:21:09 CEST 1999
    root@buoy.pdc.kth.se:/usr/src/sys/arch/i386/compile/ZEM
cpu0: Intel 486DX (486-class)
real mem  = 7995392
avail mem = 5812224
using 123 buffers containing 503808 bytes of memory
mainbus0 (root)
isa0 at mainbus0
com0 at isa0 port 0x3f8-0x3ff irq 4: ns16550a, working fifo
com1 at isa0 port 0x2f8-0x2ff irq 3: ns16550a, working fifo
wdc0 at isa0 port 0x1f0-0x1f7 irq 14
wd0 at wdc0 channel 0 drive 0: <MAXTOR LXT-340A>
wd0: drive supports 64-sector pio transfers, chs addressing
wd0: 321MB, 654 cyl, 16 head, 63 sec, 512 bytes/sect x 659232 sectors
vga0 at isa0 port 0x3b0-0x3df iomem 0xa0000-0xbffff
wsdisplay0 at vga0: console (80x25, vt100 emulation)
lpt0 at isa0 port 0x378-0x37b irq 7
we0 at isa0 port 0x300-0x31f iomem 0xcc000-0xcffff irq 10
we0: SMC8216/SMC8216C Ethernet (16-bit)
we0: Ethernet address 00:00:c0:06:8f:6d
pckbc0 at isa0 port 0x60-0x64
pckbd0 at pckbc0 (kbd slot)
pckbc0: using irq 1 for kbd slot
wskbd0 at pckbd0: console keyboard
pcppi0 at isa0 port 0x61
spkr0 at pcppi0
sysbeep0 at pcppi0
npx0 at isa0 port 0xf0-0xff: using exception 16
fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2
fd0 at fdc0 drive 0: 1.44MB, 80 cyl, 2 head, 18 sec
biomask 4040 netmask 4440 ttymask 44c2
wscons: wskbd0 glued to wsdisplay0 (console)
boot device: wd0
root on wd0a dumps on wd0b
root file system type: ffs

/Johan