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IBM PS/2 L40SX "Communications Cartridge" - How to connect it?

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mbbrutman

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The IBM PS/2 L40SX is an early IBM laptop using an 80386SX CPU. There was a wonderful sounding feature for it called the "communications cartridge" that allowed one to use an ISA network card with the laptop. The cartridge is so rare that there are no pictures of it on the Internet ... until now:

Comm_Cartridge_overview.jpg Comm_Cartridge_overview_2.jpg

So here is the problem. The connector for the L40SX looks like this:

PS2_L440SX_system_expansion_connector.jpg

The connector is 120 pins and female. I have never seen anything else like it. The connector on the communications cartridge looks like this:

Comm_Cartridge_connector.jpg

It is also 120 pins and female.

So, how does one connect this? The connector is recessed so I think that there is a cable (male on both ends) that is used to make the connection between the two. The IBM PS/Note N51SX looks to have a similar connector.

Does anybody have any ideas on what the proper name for the connector is (the form factor?) or how to find a cable for it? This does not look like something I can home brew - the pitch of the signal pins is fairly small.
 
Updates:

  • It is connected by a cable. Now I just need to find a cable.
  • A company called Axonix also made a series of expansion boxes featuring ISA slots. The boxes were generic and usable across a range of machines, if you had the right adapter for each machine.
  • The IBM L40SX requires reference disk version 1.02 (or better) to make use of the IBM expansion box, and presumably the Axonix expansion box.
  • The connector on the device ends looks to be AMP 6-175474-1. http://www.connectorpeople.com/Connector/TYCO-AMP-TE_CONNECTIVITY/6/6-175474-1 has a picture. I just need to find the male-male cable now.
 
Last edited:
And one more update ...

The cable ends look to be AMP 6-175473-1, which is described as a 120 position plug. I think I found a supplier that has them at a reasonable price, so I will learn how to make a high quality signal cable.

It's a really interesting expansion unit - I'm looking forward to getting it running and properly documenting it.
 
I'm guessing the L40SX is ISA based? Wonder if a sound card works in that box. :p
 
Mike, VERY nice find! I have two of these little beasties - the laptop, not the expansion box! Looking forward to seeing how this goes for you. I'm not 100% sure, but I think that I have the version of the reference disk that you need - I'll check and let you know.

@njroadfan, sound card would be nice, but the L40SX is not a machine that you would want to game on. It's got mono-lcd graphics on it, and refreshes are slow. I would hesitate playing even a text-based game with it, let alone a real game!
 
Maverick1978:

I got really lucky - one of the "tech warehouse" places had it. Usually they sell parts at a 10x markup. This listing had no pictures and the price was cheap enough to make me believe that it was a mislabeled part. So except for not having the cable, I'm extremely happy that the gamble paid off. (Once in a while it has to pay off ... I've been hosed enough times.)

I have version 1.03, so I think I'm covered. But when the time comes, I'd like to be able to post all of the versions on a web page. So make sure you have that diskette backed up.

I still have the cable problem. I found the connectors and I can purchase them. But I don't know the wiring. I'm assuming it is straight through, but I really need to find a technical reference for both the laptop and the expansion box. Or at least one of them would be nice ... otherwise, my default will be to wire the cable straight through and pray, or wait until I can find a sample of the cable. A pinout for the "Communications Cartridge II" used by the PS/2 Note N33 would probably work too. (There is no cable on that unit, but it is supposed to be similar to the L40SX.) Or of course a cable for the old Axonix boxes.


njroadfan:

The expansion unit takes ISA cards, but 8 bit only. The machine has a 386SX CPU at 20Mhz, but being a laptop it has no standard slots in it. The edge connector has enough pins to support ISA. And there is VGA out, so the screen situation is not totally terrible.
 
That connector looks quite similar to a VHDCI connector. 68-pin VHDCI connectors are commonly used on SCSI cards, and I've seen 34-pin VHDCI sockets so I guess there are other sizes too? Maybe you can get a 120-pin VHDCI connector somewhere. If you have a 68-pin SCSI one handy it'd be interesting to see whether it starts to fit into the socket or whether it's completely different beyond just the width.

If you do a Google image search for "vhdci receptacle" then there are a few good pics.
 
I decided to pick this project up again this weekend; I was ordering PCjr sidecar connectors so I might as well get these connectors too. Ugh, what a mistake ... this problem is the perfect example of why I stay away from PS/2 hardware.

First, I can't find any cable that looks like this. It's a docking connector so it's not really meant to be attached to a cable. I have no idea why IBM used a cable, but they probably thought better of it too and eliminated the cable on the next generation of these devices used with later portable machines.

The IBM cable part number is 06G8069 if it ever comes up at a dinner party ...

I'm ordering connectors but I really don't want to try to build a cable without the pinout. That's just asking for a disaster, and I don't want to damage the machine. I need to find either an existing cable so that I can determine the pinout from it directly or technical documentation for the expansion port and this device so that I can design a cable from scratch. Just assuming an off the shelf cable will work is too risky.

I took apart the adapter and traced the pins from the ISA slot to the connector; at least that part was straightforward. Here are pictures of the internals if anybody is interested:

IBM_Communications_Cartridge_circuit_top.jpg



IBM_Communications_Cartridge_circuit_bottom.jpg



If anybody has one of these please let me know. I'm willing to bribe to see the pinout of the cable! I know IBMMuseum had one, but he has not been active on the forum in a few years.
 
I found somebody who had a cable and was willing to loan it to me for the purpose of getting a pinout.

Here is what the cable looks like:

L40SX_Cable.jpg

The complicated end is a cam mechanism that locks the cable to the back of the laptop quickly; it is more convenient than twisting thumb screws. The side with the conventional thumb screws goes to the expansion unit and presumably stays connected there, hence the lack of an easier to use locking mechanism.

The connectors were as I thought. I'll attach a pinout after I clean up my notes.
 
I've got two of these for sale, one is just the communications enclosure, the other is complete with cables, box and docs.
 
chulofiasco said:
I've got two of these for sale, one is just the communications enclosure, the other is complete with cables, box and docs.
Click to expand...

Asking price?

Have you considered scanning the docs and posting them publicly? These things really are hard to come across ...
 
Right now I don't really have an asking price, i'll take offers though. I had thought about posting it on fleabay, but i haven't gotten around to it.

that's a good idea about scanning the material, i might do that. i'll check it out.
 
Thanks for doing that - it was helpful! The manual showed the difference between the two cable part numbers.

Do you have an L40SX to use these with? If so, did you have problems with system stability? I got mine to work with a borrowed cable but the system was flaky - the hard drive would appear and disappear, and writes to it would sometimes corrupt it. This only happens with the expansion unit connected.

I have some debugging to do ..
 
I've got some L40SX to use it with, but I've been doing my IBM experiment in chunks. I started with the models 25 and 30 and once I felt pretty confident with those, I moved to the 90 and 95. I'm presently stuck on that and the variety of adapter options available. I have a 9595 and an 8525 at home, and they're both beast machines. Maybe it's time for a break.. lol
 
chulofiasco said:
I've got some L40SX to use it with, but I've been doing my IBM experiment in chunks. I started with the models 25 and 30 and once I felt pretty confident with those, I moved to the 90 and 95. I'm presently stuck on that and the variety of adapter options available. I have a 9595 and an 8525 at home, and they're both beast machines. Maybe it's time for a break.. lol
Click to expand...

Let me know when you get to the L40SX. There are not many surprises; the original hard drives have all since died but replacing them is fairly easily. The CMOS battery is hard to get at so it's good to replace it at the same time you do the hard drive replacement.

The communications cartridge looks like a nice add-on but it's not necessary for general use. I'm kind of a networking freak so I wanted to see how the machine would be have with Ethernet. It worked, but the machine was not stable. It's going to take me a little while to figure out what causes the instability; old dried-out capacitors are a possibility.
 
https://goo.gl/photos/nsdPsBaeSjYF3c8G8

I finally got the Communications Cartridge working tonight. Here is the summary:

  • My first L40SX hates it; the hard drive won't run correctly with the communications cartridge attached. It's not a conflict because the cartridge did not have an ISA card in it. I suspect the machine is marginally healthy or it has a downlevel firmware. (Does anybody have the firmware updates for the machine?)
  • My second L40SX seems to be compatible with the cartridge. I have an NE1000 card sitting in it now running mTCP IRCjr. It's been running for over an hour.
  • Performance is quite good ... mTCP spdtest reports that it can send and receive using the NE1000 card at about 350KB/sec.

So now to figure out what's wrong with the first L40SX ...
 
I am also interested in using the Communications Cartridge with my L40SX, I would like to use it with a sound card, adlib or anything that is better than the beeper that comes with L40SX. Just for fun.

Any tips on how to get a Communications Cartridge?

Also, from looking at the photos (thanks to mbbrutman for putting them on the Internet) it does not look like a piece of complex hardware. I am willing to reverse engineer it, and make a pcb to clone the functionality. But then I would need at least access to one of the originals. Anyway, if anyone wants to help/cooperate. Let me know! The reverse engineering/developing the PCB probably takes me 5 years, but it will be a nice side project for me. Thanks!
 
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