collisions 200% of Tx on 10BaseT (21140, .90q, Samsung SC1200-TX)

[Monty]

Hello folks,

I just replaced a Lite-On due to poor performance with a Samsung
SC1200-TX after noticing the genuine DEC Tulip onboard (a 21140).

My net here is 10baseT; I bought the 100Mbps capable Tulips as they're
reputed to be cheap and hardy.  However, the Samsung card displays one
extremely annoying behavior; when doing heavy receiving (for example,
FTP downloads from another machine on the same subnet), it collides on
just about every transmit (the TCP acks).  The "collision" light on
the hub is on solid.  ffconfig confirms the diagnosis; it collides
more often than it successfully transmits (all this documented below).
The reverse does not seem to be a problem; heavy uploads (mostly large
transmits, very few receives) show no collision behavior. I've used
.90q and .90p.  Note that the de4x5 driver shows the same behavior.

All the cabling has been checked and replaced. I also replaced the hub
(a "Hawking" cheap noname) with a Netgear hub temporarily "just to
make sure".  The Lite-On based card didn't seem to have this problem,
but its performance wasn't even keeping up with 10baseT so...

Any ideas?  Do I try yet *another* tulip?

diagnostics and ifconfig results follow.

Monty

----->8-----

SnotFish:/usr/src# /sbin/ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:40:05:A5:0E:B3  
          inet addr:10.0.0.1  Bcast:10.255.255.255  Mask:255.0.0.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:150237 errors:0 dropped:0 overruns:0 frame:0
          TX packets:30221 errors:0 dropped:0 overruns:0 carrier:0
          Collisions:53584 <----(low actually; I was also uploading, 
	                         which does not cause collisions)
          Interrupt:12 Base address:0xfc00 

SnotFish:/usr/src# ./tulip-diag -f -e -e -a -m -m
tulip-diag.c:v1.08 2/28/99 Donald Becker (becker@cesdis.gsfc.nasa.gov)
Index #1: Found a Digital DS21140 Tulip adapter at 0xfc00.
Digital DS21140 Tulip Tulip chip registers at 0xfc00:
  ffa08000 ffffffff ffffffff 00f7f028 00f7f228 fc6e0000 320e2002 ffffebef
  e0000000 fffd83ff ffffffff fffe0000 ffffff80 ffffffff 1c09fdc0 fffffec8
 Port selection is MII, half-duplex.
 Transmit started, Receive started, half-duplex.
  The Rx process state is 'Transferring Rx frame into memory'.
  The Tx process state is 'Idle'.
  The transmit threshold is 128.
EEPROM contents:
  1099 1100 0000 0000 0000 0000 0000 0000
  00e0 0103 4000 a505 b30e 1e00 0000 0800
  0100 018c 0000 0000 e078 0001 0050 0018
  0000 0000 0000 0000 0000 0000 0000 0000
  0000 0000 0000 0000 0000 0000 0000 0000
  0000 0000 0000 0000 0000 0000 0000 0000
  0000 0000 0000 0000 0000 0000 0000 0000
  0000 0000 0000 0000 0000 0000 0000 da5c
 ID CRC 0xe0 (vs. 0xe0), complete CRC c5a4ded3.
EEPROM transceiver/media description for the Digital DS21140 Tulip chip.

Leaf node at offset 30, default media type 0800 (Autosense).
 CSR12 direction setting bits 00.
 1 transceiver description blocks:
  Media MII, block type 1.
   MII interface PHY 0 (media type 11).
  21140 MII Reset sequence is.
  21140 MII initialization sequence is.
   Media capabilities are 0000, advertising 7801.
   MII interrupt on GPIO pin -1.
 MII PHY found at address 0, status 0x782d.
 MII PHY #0 transceiver registers:
   1000 782d 7810 0001 01e1 0021 0000 0000
   0000 0000 0000 0000 0000 0000 0000 0000
   0000 0000 4000 0000 2089 0010 0000 0002
   0001 0000 0000 0000 0000 0000 0000 0000.
 Basic mode control register 0x1000: Auto-negotiation enabled.
 Basic mode status register 0x782d ... 782d.
   Link status: established.
   Capable of  100baseTx-FD 100baseTx 10baseT-FD 10baseT.
   Able to perform Auto-negotiation, negotiation complete.
 Vendor ID is 1e:04:00:--:--:--, model 0 rev. 1.
   Vendor/Part: Level One LXT971.
 I'm advertising 01e1: 100baseTx-FD 100baseTx 10baseT-FD 10baseT
   Advertising no additional info pages.
   IEEE 802.3 CSMA/CD protocol.
 Link partner capability is 0021: 10baseT.
   Negotiation did not complete.