Ref: 11630016
Title: Converting 8088 PCs from 3+ to 3+Open using Programmed I/O
Date:  12/17/90

Copyright 3Com Corporation, 1991.  All rights reserved.

After years running 3+ on 8088 compatibles, you are now migrating to 3+Open.
The DMA settings on the EtherLink II and EtherLink Plus cards you had used
in 3+ are not working under 3+Open, causing the PC not to function properly.
Reported problems include floppy drives not performing standard I/O functions
and generating "Sector not found" or "Drive not ready" messages.  Here is
information that can help you solve those problems.


The EtherLink II and an 8088 machine:

Under 3+, if your PC with an EtherLink II card had a CONFIG.SYS line that
read DEVICE=ETH503.SYS /M:2 ..., the parameter /M:2 told the computer to use
Programmed I/O (PIO).

For PIO to be implemented in 3+Open, add the line DATATRANSFER=PIO_BYTE in
the EtherLink II section of PROTOCOL.INI.  The 3+Open LAN Manager Technical
Reference (P/N 5149-00) states:

      PIO_BYTE =  Transfer mode for 80286 and 80386 computers.
                  Sometimes used to slow data transfer on a very
                  fast 80386 computer.

PIO_BYTE will also work in an 8088 machine.  Adding this parameter overrides
the default of Burst or Demand_DMA; instead, programmed I/O is used to
transfer data between the EtherLink II's 8 KB RAM and the machines's main
memory.

An alternative to PIO would be to use shared memory on the EtherLink II.
To do this on the EtherLink II card, there are memory jumpers that read:

                Disable
                DC000
                D8000
                CC000
                C8000

To put the card into shared memory mode, change the jumper from "Disable" to
another address.  The DATATRANSFER= and DMACHANNEL= parameters will be
ignored in PROTOCOL.INI.  The EtherLink II will occupy 8 KB of computer high
memory at C8000, CC000, D8000, or DC000.  Therefore, it is important to be
sure the memory space accessed by the EtherLink II adapter does not conflict
with anything else in the machine.

It is better to use the EtherLink II in shared memory mode, because shared
memory mode will optimize the performance of the card and the 8088.  Shared
memory maps the 8 KB RAM on the card to be accessible directly by the host
processor.


The EtherLink Plus and an 8088 machine:

Under 3+, your XT with an EtherLink Plus card was set to Interrupt 3,
I/O address 300, DMA 1.  Booting under 3+Open running XNS, these default
settings work fine.  However, booting under NBP, the machine does not
function properly.  3Com has seen problems with the floppy drive; for
example, formatting a floppy disk in drive A: will generate bad sectors.

To remedy this, use the parameter DATATRANSFER=PIO_BYTE to change the data
transfer mode from DMA to Programmed I/O.

Note:  For ATs experiencing similar problems with the EtherLink Plus
card in a 16-bit slot, you can use DATATRANSFER=PIO_WORD.

You can use the same DATATRANSFER settings for the EtherLink Plus as shown
for the EtherLink II in the 3+Open LAN Manager Technical Reference.

