View source for Making a PS/2 Ethernet Adapter work in a 5494


The 5494 Remote Control Unit supports a Microchannel Ethernet LAN Adapter. This adapter can provide two different functions:

- It can connect twinax terminals (and PCs with twinax emulation cards) to 1-4 AS/400 systems connected to an Ethernet network; or

- It can connect locally-attached Ethernet LAN systems to 1-4 AS/400 systems over the 5494's communication line 9V.24/X.21/V.35).

IBM supports ONE specific Ethernet adapter in the 5494 - PN 10H4633. This card is electrically identical to the IBM LAN Adapter/A for Ethernet, supported in PS/2 systems. However the Microchannel Card ID is different between the 5494 card and the PS/2 card, so putting a PS/2 LAN Adapter in a 5494 will not work.

The 5494 version of this LAN card nowadays is EXTREMELY rare. The PS/2 version of the same hardware is relatively obtainable still.

In researching the differences between the two cards, we discovered that the only difference between the two cards is the Microchannel Card ID, and discovered that it is possible - with some effort - to "renumber" a PS/2 LAN card to work in a 5494.

There are two PS/2 LAN card versions:

- A "long" card: https://www.ardent-tool.com/NIC/LAN_A.html#LAN_A-Old

- A "short" card: https://www.ardent-tool.com/NIC/LAN_A.html#LAN_Adapter/A


It is possible to modify these cards to work in a 5494 by programming a new ID PROM chip. The chip on these boards is a small PLCC-20 pin surface mounted component and is non-trivial to remove and replace. However, both cards have a socket for an RPL/BOOT ROM chip that carries all but one of the required board signals, and the boot ROM is not used for the 5494 and needs to be removed anyway.

The basic hardware modification is not trivial, but not insurmountable for anyone with some soldering skills.

You will need:

- A soldering iron with a fine tip

- Some solder (fine electronic rosin-core solver of almost any type)

- Chip-Quik SMD Removal kit (optional, but helpful)

- One 28 pin DIP chip socket (of the "square pin" variety)

- One programmable ROM chip of the 2764/27128/27256 type or any equivalent

- A way to program the aforementioned PROM

- Some fine wire, 28-30 gauge

- An X-acto knife with a pointed blade or an extremely small bladed flat tip screwdriver

- Hot Glue Gun (optional, but recommended)



Step 1: Remove the RPL/BOOT PROM from the board. It's the large 28 pin chip in the socket.
PRO-TIP: You won't need this ROM anymore and it's the right type for this modification, so if you have an EPROM eraser, erase this chip and you can reuse it.



Step 2: Find U5 on the PCB. It's a small square chip. On the short LAN card its directly above the ROM socket. On the long card it's near the crystal along the top edge of the board. The chip has a part number sticker on the top of it, and it's IMPORTANT to note its orientation on the board - the chip has a beveled edge on one edge. That edge is "upright" on the short board, and the bevel is on the "right" side of the chip on the long card.



Step 3: Use an X-Acto knife with a pointed blade, or some other extremely small blade or screwdriver to get under the leg of the chip that is FARTHEST TO THE RIGHT along the beveled edge of the chip. Heat that one pin with a soldering iron, and when it's hot, gently pry the pin out from under the chip and off the board. The pin curls under the chip somewhat, so the lead is a little longer than you would expect. Make sure the pin on the chip is well clear of the board and pads. Repeat this step with the SECOND RIGHTMOST PIN along that same edge. When you are done you'll have three pins on the beveled edge of the chip still in place and the two pins on the right clear of the board. If you have any Chip-Quik, a little of the flux and solder in that kit will make lifting these 2 pins significantly easier, but it's doable without it.



Step 4: Strip and tin the end of a piece of fine gauge wire. For the long board the wire should be at least 6 inches for the short board the wire should be about 2 inches. It'll need to reach the 28 pin socket on the board, and you can trim it later, don't be stingy. Clip the tinned and exposed portion to only 1-2mm of exposed wire, and solder it to the RIGHTMOST PAD on the BOARD, under the pin you removed. Be careful to not bridge the wire to the other exposed pad or any other pins or the pins you lifted from the board. This takes a little bit of a steady hand, the pad on the PCB is very small. Leave the other end of the wire, we'll come back to it later.

[[File:54IDPROMaltered.jpg|480px]]



Step 5: Using a small pair of needle nose pliers or some other tool, use the tool to "push" the following pins up from the bottom of the DIP socket to remove them from the plastic holder. This disconnects the unneeded pins on the BOOT PROM socket from the modified ID PROM that's going to take its place. Remove pins 1, 2, 3, 4, 5, 6, 21, 23, 24, 25, 26, and 27. BEND pins 20 and 22 90 degrees to the outside of the socket so the pins are exposed out of the side of the socket.



Step 6: Insert the modified socket into the BOOT PROM socket on the board, lining up the Pin 1 markings on the board. Route the wire you connected under the ID PROM to the socket and solder it to the two pins sticking out of the side of the socket (pins 20 and 22 from the previous step).

[[File:5494modifiedsocket.jpg|480px]]


Step 7: Optional but recommended: Use a hot glue gun to tack down the patch wire to the board, and a bead of hot glue to stick the modified DIP socket onto the socket on the board. Be sparing - a little hot glue goes a LONG way!



Step 8: Program the new ID PROM. Open your favorite ROM programming software, set the device type to the ROM you're going to program (the BOOT PROM, if you're reusing that one, is a 27128). Clear the buffer in the software and enter the following 32 bytes into the ROM buffer starting at address 0x0000:

0x0000 E6 FE 00 06 29 xx xx xx 00 00 00 00 00 00 5A yy

0x0010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

IMPORTANT! Replace the 'xx xx xx' above with the last 3 bytes of the Ethernet MAC address of the card (if you know it). If you don't know it, find the serial number label on the card and use the last 6 digits in the serial number. If you can't find that, pick your favorite 3 hex bytes and use that for an address.

ALSO IMPORTANT! Replace the 'yy' with the "8 bit checksum" for that line of bytes. The checksum number is the number that makes that line of bytes add up to a hex number ending in '00' - see http://easyonlineconverter.com/converters/checksum_converter.html for a quick calculator.

Here's an example of a "correct" ROM and it's checksum:

0x0000 E6 FE 00 06 29 05 96 82 00 00 00 00 00 00 5A 76 <- all these bytes add up to 0x400

0x0010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[[File:5494romchecksum.png|480px]]

Your final modification should look something like this:

[[File:5494lancardfull.jpg|480px]]



Step 9: Insert the modified ROM into the modified socket, in the BOOT PROM socket on the PCB.

The board now can be installed in a 5494 and configured.

[[File:5494lancardid.jpg|480px]]

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