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JollyRogers
October 11th, 2008, 03:40 PM
I have an asynchronous communication card in my XT, and there's a ribbon cable running from it to a female DB25 port on a plate at another expansion slot. My question is, does the female DB25 port act as a serial port or parallel port?

tezza
October 11th, 2008, 05:41 PM
Hmm..a female DB25 (with holes that the pins go into) in normally associated with a parallel port on old IBMs. However the asynchronous communication cards I'm familiar with all have male DB25s and they are serial?

Tez

paul
October 11th, 2008, 07:32 PM
It must be an aftermarket card with the auxiliary DB25, not an original IBM, and it's definitely a parallel port. Other than the original PC serial card I don't recall any ISA-bus communications cards using anything other than a DB9 for serial.

Druid6900
October 11th, 2008, 08:10 PM
You must be pretty young then, because, at one time, parallel ports were DB25F and serial ports were DB25M. The only DB9s were video.

IBMMuseum
October 11th, 2008, 08:37 PM
You must be pretty young then, because, at one time, parallel ports were DB25F and serial ports were DB25M. The only DB9s were video.

Exactly, the AST adapters had DB-25s for serial connections. The AT is what actually *started* to bring in the DB-9M for serial. Even then, I still have quite a few DB-25M connections on a 10-pin header to use the šold-styleš connections.

MikeS
October 12th, 2008, 09:16 AM
As a matter of fact, many of the multi-IO cards had one of each (9 and 25 pin).

Except for a few early sort-of-compatibles, in the PC world the parallel port has always been a 25-pin female, and the serial port(s) either 9 or 25 pin male. BTW, the gender refers to the pins (the shell is actually the opposite gender).

A female DB-25 on an async card is definitely an oddity; either there's also a parallel port on the card, or someone has made a custom cable or used a printer cable instead of the serial.

If by female you are indeed referring to holes for the connecting pins then it's definitely non-standard and I'd check it out further before connecting something and possibly causing damage.

m

JollyRogers
October 13th, 2008, 03:56 PM
I can take a photo if it helps, but basically the card has a male DB25 on it, then a small ribbon cable running to a DB25 female. I'm considering just hooking a printer up and seeing what happens. Worst case scenario, I have another Asynchronous communication card.

MikeS
October 13th, 2008, 04:12 PM
Well, if anything does get damaged in your worst case scenario it's actually more likely to be the printer.

Sounds like you may have a printer cable on the second port instead of the DB-25M serial. A picture would be good, especially if we can see the main chip numbers; if there are just two UARTs then they're both serial. Maybe someone wanted to plug in a male serial cable and didn't want to use an adapter.

If you've got a meter you could measure the voltages on the external DB25 and compare them to the one on the card.

m

channelmaniac
October 13th, 2008, 09:57 PM
It's easier than that usually...

99% of the serial ports I've seen over the years have had a 9 pin ribbon cable connecting it. Does the one you have on the computer have only 9 pins on the ribbon cable? If so, it's serial.

RJ

Druid6900
October 14th, 2008, 07:44 PM
It's easier than that usually...

99% of the serial ports I've seen over the years have had a 9 pin ribbon cable connecting it. Does the one you have on the computer have only 9 pins on the ribbon cable? If so, it's serial.

RJ

All the ones I've seen have 10 pin headers regardless of the DB shell pin count. A parallel port header will have 26 (2 x 13) pins on the header and the game port, a 16 pin header.

kb2syd
October 15th, 2008, 06:01 AM
To really confuse things, Radio Shack manufactured serial cards with 25 pin female connectors for quite a while too. I had one here in my 1200 hd for years.

Druid6900
October 15th, 2008, 08:06 PM
Yup, got the same one in my 1200HD

@ MikeS, do you have a Tandon TM-100-2A? I had to sacrifice mine to fix that damn Model 4D.

Terry Yager
October 15th, 2008, 08:22 PM
To really confuse things, Radio Shack manufactured serial cards with 25 pin female connectors for quite a while too. I had one here in my 1200 hd for years.

Perhaps to maintain 'plug compatibility' with earlier computers (Kaypro, Morrow, TRS-80, etc) which used female 25-pin DIN jacks for serial ports?

--T

MikeS
October 16th, 2008, 09:58 PM
@ MikeS, do you have a Tandon TM-100-2A? I had to sacrifice mine to fix that damn Model 4D.
----
What's the 'A' mean?

I've got some TM100s, FH 48TPI/DD as used in PCs, if that'll do ya; might need alignment though...

m

Druid6900
October 17th, 2008, 02:56 PM
----
What's the 'A' mean?

I've got some TM100s, FH 48TPI/DD as used in PCs, if that'll do ya; might need alignment though...

m

I have NO idea what the 'A' stands for. As long as it'll do 360K, I'm sure the 1200HD won't mind a bit.

Alignment? No problem, I'm just going through a stack of Texas Peripheral SSDD drives (10-5355-001) aligning them

JollyRogers
October 21st, 2008, 09:19 PM
So, I was inside my XT today and found out that the serial card in question was in fact a SixPakPlus! (Turns out my motherboard is the 64-256KB board, not the 256-640KB board I thought it was) The DB-25 Female port is indeed an LPT port. Mystery solved, and would have been solved sooner if only I knew more about machines of this age. Live and learn I suppose.