View Full Version : Modem for XT computer.

August 31st, 2006, 12:36 AM
I want to buy analog modem.

It's hard to setup it under XT machine?

I can choose from:


http://allegro.pl/item122882258_modem_wewnetrzny_isa_zoltrix_bcm_.ht ml



August 31st, 2006, 06:02 AM
I think you should be looking for an old Hayes 1200 or 2400 external modem. Nothing faster than 9600 though .. the XT would have a hard time keeping up with it.

August 31st, 2006, 11:08 AM
If you want to go crazy for several hours, all the US Robotics 56K modems that I own can be forced to connect only at 2400 or 9600. Long time ago you could use the dip switches to set the local uart speed, with the more modern jobs, gotta be some "AT" commands to do it. On the down side, you will frequently get booted off the connection if you only connect at 9600 or 2400.

August 31st, 2006, 11:51 AM
old Hayes 1200 or 2400 external modem

You mean these big old boxes? :)
Will be hard to find one...

I have 54K robo~ modem, but I want old one.

August 31st, 2006, 12:16 PM
Big old box? Hardly. Nice brushed aluminum box that fit under the standard desk telephone of the 1980s. May 1.5 inches high, 7 inches wide, and 10 inches deep.

August 31st, 2006, 12:53 PM
I have 8-bit US Robotics modem, 28.8... but I never tried it in XT yet.

August 31st, 2006, 01:07 PM
My XT with the external hardfile has a modem in it...dunno anything about it yet.

September 1st, 2006, 12:46 AM
Big old box? Hardly.

There were modems like this, but they was propably much slower.

Thanks, I'll look for the modem.
And, can I use it for something more than IRC?

the xt guy
September 1st, 2006, 09:56 AM
mbbrutman is right, 9600 is the fastest you should try with an 8088 running at 4.77 mhz. Anything much faster and the CPU will not be able to cope.

With an xt clone motherboard (faster CPU), you should be able to use a faster modem. My 10mhz. XT clone runs at about 2.5x the speed of a 5150/5160, so I could probably get away with modem speeds up to about 24k or so.

Right now, I have a 14.4k internal modem in it and it works OK. I haven't tried replacing it with a 28.8k modem to see if it will be faster.

You can use an external modem, but it will be probably limited to about 9600 bps, as the 8250 uart chip in the serial port is limited to this.

An internal modem will bypass this limitation.

Even though I have cable Internet, I keep a dial up ISP connection as well. it's only $6.95 a month, and an 8088 running DOS works just fine with them (no Win-based software needed).

September 1st, 2006, 10:27 AM
As suggested so far, with an external modem you would be sure it is not a controller-less ("HSP", "Win Modem", etc.) design, which would be a bad thing with an XT-class system. If selecting an internal (and all the speed comments are right on too) modem I would make sure it has a discrete UART ("8250" on a typically 40-pin DIP chip), although there are many modem chipsets that emulate the UART. For your location in Poland the older modems are going to be in a computer surplus place or hobbyist's house if at all, not new off the shelf.
I happen to have about three good-sized boxes full of all sorts of different types...

September 1st, 2006, 10:33 AM
Just to clarify, by 9600 bps recommendation is based on using a modem and a terminal emulator.

The 8250 UART in the XT can be tricked into going a heck of a lot faster using creative assembly language coding, but you can't drive it fast if you are writing output to the screen.

(Early data transfer programs used null modem cables between PCs and drove the port as high as 115200 bps.)

Mike Chambers
September 2nd, 2006, 01:42 AM
if you just want an XT-compatible modem for connecting to the internet, i suggest you just find an old 8-bit ISA NE1000/NE2000 compatible ethernet card

September 2nd, 2006, 07:16 AM
Hang on .. some wires got crossed in that post.

I think Mike was referring to XT-compatible Ethernet card, not a modem ..

The Etherlink II from 3COM and the Western Digital 8003 series also work in 8 bit slots.

Mike Chambers
September 2nd, 2006, 04:37 PM
Hang on .. some wires got crossed in that post.

I think Mike was referring to XT-compatible Ethernet card, not a modem ..

The Etherlink II from 3COM and the Western Digital 8003 series also work in 8 bit slots.

yeah, i was. sorry, i should've been more specific.

oh, out of curiosity do you know if the 16-bit 3com Etherlink III is also 8-bit compatible? i'd like to use it in my 8088 instead of the NE1000 compatible card (which is 8-bit only) that i have, because it seems to intermittantly stop working.. i think something loose in it's RJ45 port.

September 2nd, 2006, 05:33 PM
I've not tried the Etherlink III in an 8 bit slot. On the other hand, there is a seller on eBay selling lots of 10 Etherlink IIs for a rediculously low price. I posted a heads up about it here already - look for 3C503.

Those don't have RJ45 ports though - only AUI.


September 2nd, 2006, 11:13 PM
I have posibility to get acoustic modem ;).
When they were used?

In pre-Pc era?

September 3rd, 2006, 02:20 AM
I have an Etherlink III with RJ45 connector. I'll try it in my XT later...