> > I have checked my card's behaviour after I posted the last mail,
> > and found that it tries to resend the same packet which is already
> > sent. Probably this behavior causes the transmit underflow...
> > 
> > BTW, I use it with LX chipset mainboard and PII-233MHz.
> 
> What other DMA devices do you have ?

Here I list DMA devices as far as I know...

As for ISA devices, a sound card & fdc use DMA.
As for PCI, pciide, usb, and network, but currently I don't
use any USB devices.
And I use XPERT@Play (3D rage pro) as my video card on AGP slot.

Would these be some hints?

And message below is my system's dmesg output.

==============================
NetBSD 1.3H (MYOKEN) #75: Mon Nov  2 19:04:55 JST 1998
    kouchi@myoken.kuis.kyoto-u.ac.jp:/usr/src/sys/arch/i386/compile/MYOKEN
cpu0: family 6 model 3 step 4
cpu0: Intel Pentium II (686-class)
real mem  = 66715648
avail mem = 60145664
using 840 buffers containing 3440640 bytes of memory
mainbus0 (root)
pci0 at mainbus0 bus 0: configuration mode 1
pci0: i/o enabled, memory enabled
pchb0 at pci0 dev 0 function 0
pchb0: Intel 82443LX PCI AGP Controller (PAC) (rev. 0x03)
ppb0 at pci0 dev 1 function 0: Intel 82443LX AGP Device (PAC) (rev. 0x03)
pci1 at ppb0 bus 1
pci1: i/o enabled, memory enabled
ATI Technologies product 0x4742 (VGA display, revision 0x5c) at pci1 dev 0 function 0 not configured
pcib0 at pci0 dev 7 function 0
pcib0: Intel 82371AB PCI-to-ISA Bridge (PIIX4) (rev. 0x01)
pciide0 at pci0 dev 7 function 1: Intel 82371AB IDE controller (PIIX4)
pciide0: bus-master DMA support present
pciide0: primary channel wired to compatibility mode
atapibus0 at pciide0 channel 0
cd0 at atapibus0 drive 1: <Pioneer CD-ROM ATAPI Model DR-A24X  010, , E1.04> type 5 cdrom removable
cd0: using 32-bits pio transfers
cd0: PIO mode 4, DMA mode 2
wd0 at pciide0 channel 0 drive 0: <IBM-DHEA-34330>
wd0: using 16-sector pio transfers, lba mode
wd0: 4134MB, 8400 cyl, 16 head, 63 sec, 512 bytes/sect x 8467200 sectors
wd0: using 32-bits pio transfers
wd0: PIO mode 4, DMA mode 2, UDMA mode 2
pciide0: secondary channel wired to compatibility mode
pciide0: disabling secondary channel (no drives)
wd0(pciide0:0:0): using PIO mode 4, UDMA mode 2
cd0(pciide0:0:1): using PIO mode 4, DMA mode 2
uhci0 at pci0 dev 7 function 2: Intel 82371AB USB Host Controller (PIIX4) (rev. 0x01)
uhci0: interrupting at irq 11
uhci0: USB version 1.0
usb0 at uhci0
uhub0 at usb0: Intel UHCI root hub (class 9/1) (rev 1.00/1.00) (addr 1)
Intel 82371AB Power Management Controller (PIIX4) (miscellaneous bridge, revision 0x01) at pci0 dev 7 function 3 not configured
de0 at pci0 dev 10 function 0
de0: interrupting at irq 10
de0: MX98713 [10-100Mb/s] pass 0.0
de0: address 00:40:05:50:f8:d2
de0: enabling 100baseTX port
isa0 at pcib0
com0 at isa0 port 0x3f8-0x3ff irq 4: ns16550a, working fifo
pcppi0 at isa0 port 0x61
spkr0 at pcppi0
sysbeep0 at pcppi0
isapnp0 at isa0 port 0x279: ISA Plug 'n Play device support
npx0 at isa0 port 0xf0-0xff: using exception 16
vt0 at isa0 port 0x60-0x6f irq 1
vt0: generic, 80 col, color, 4 scr, mf2-kbd, [R3.32]
vt0: console
fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2
fd0 at fdc0 drive 0: 1.44MB, 80 cyl, 2 head, 18 sec
isapnp0: read port 0x203
ym0 at isapnp0 port 0x220/16,0x530/8,0x388/4,0x330/2,0x370/2 irq 5 drq 0,1
ym0: OPL3-SAX Sound Board : OPL3-SA3
audio0 at ym0
joy0 at isapnp0 port 0x201/1
joy0: OPL3-SAX Sound Board 
joy0: joystick not connected
apm0 at mainbus0: Power Management spec V1.1 (slowidle)
apm0: A/C state: on
apm0: battery charge state: no battery
biomask 4840 netmask 4c40 ttymask 4c42
boot device: wd0
root on wd0a dumps on wd0b
root file system type: ffs