Hi, this reminds me of an older thread. 😀
A Null-Modem is a Null Modem, right?

BeginnerGuy wrote:

As another last ditch, my case has a male DB9 port on with a 10 pin connector for the
controller card, I tried connecting that up to one of the serial headers on my controller card and re-enabling com2,
but still no luck. (even though com1 and com2 are detected)

Hmm. Not sure why it does not work, sorry. 🙁
Maybe your DB9 (or DE9 -> shell size) plug uses a non-standard wiring ?
I mean, the 486s days were quite chaotic, so that might be possible.

The serial cable works if i plug it into com1, can fire up a multiplayer doom match no problem. Issue is I want a mouse too.

I'm not sure, i'm trying to see if there are any conflicts on IRQ 3 but nothing I can find. Sound blaster is at IRQ 5. Only card I'm unsure of is the 3com Etherlink III 3c509 but I don't believe that would use 3.

I took a second working VLB card and disabled everything except it's com port which i set to com2 but it won't work with my mouse or the null modem cable (works with both if i use it on it's own). That tells me all the cabling is right, something has to be conflicting. Unfortunately it seems IRQ 3 and 4 are the only ones available for com1-2 on both cards.

I'm stumped.

I'm checking amazon for other cables and they have Null modem cables that go from DB9 FEMALE to DB25 MALE, That would be LPT1 on this computer. I don't see that working for a game like doom which looks for COM ports 😵

little update: I've gotten it to where using two VLB controller cards, i can get com2 to see the mouse and install the driver, but the mouse wont work. Null modem also wont work in that port. Both will work through the card with COM1. MSD reports the com ports at the proper addresses for com1 and com2. I'm thinking I'm going to order an ISA card with 2 more db9 ports but i'm worrying that may not solve the problem since no setup combination seems to get com2 to work.

One last idea to try tomorrow then I give up haha

Resource-wise, you should be fine. I ran DB9 - COM1 3F8/IRQ 4, DB25 - COM2 2F8/IRQ 3, Modem COM4 - 2E8/IRQ 2 back in the day. The modem was the oddball as I wanted both serial ports and an internal modem and therefore used the cascading IRQ 2/9 for the interrupt. Worked fine for my needs at the time.

You can adapt the cable at the port end for use with your db25 port. I don't think you need to worry about messing with dual DB9s - but regardless, you need to make sure your resources are happy (as you already know)

CkRtech wrote:

Resource-wise, you should be fine. I ran DB9 - COM1 3F8/IRQ 4, DB25 - COM2 2F8/IRQ 3, Modem COM4 - 2E8/IRQ 2 back in the day. The modem was the oddball as I wanted both serial ports and an internal modem and therefore used the cascading IRQ 2/9 for the interrupt. Worked fine for my needs at the time.

You can adapt the cable at the port end for use with your db25 port. I don't think you need to worry about messing with dual DB9s - but regardless, you need to make sure your resources are happy (as you already know)

What I can't understand is why the serial port integrated in my case won't work with either COM1 or COM2, it has the same header as the DB9 connector built right onto my i/o controller card, and it worked just fine with the serial header on a later AT/ATX socket 7 board I originally had in this case. But if I swap it with the db9 port that works, it doesn't work.. This is really just leaving me scratching my head..

Anyway, I'm going to just grab either an i/o card or adapter.. The adapter is so cheap I think i'll just grab it and hope it solves my problem. I'm assuming the cable would still retain it's NULL characteristic even with the adapter since the pins should stay reversed, though I'm too tired and lazy to draw a diagram to make sure right now.. I just hope one of the two DB25 male ports I have will work with one of my two controller cards and end this nightmare for me 😒

https://www.ebay.com/itm/New-SIIG-Serial-Adap … YIAAOSwd0BV6LXr

https://www.amazon.com/Belkin-F2L087-Female-S … +to+db25+female