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8 bit isa modem

E

erikk1971

New Member
Joined
Nov 2, 2008
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6
I get a few half isa modems alot are usr. Two tested an recognized as 56k.

What speed modem will work in xt 268 386,

I keep these modems figuring one day someone might one.

I also got several isa sound cards creative labs.

I was told the sound blaster cards were better.
 
I tried to clean it up a bit. Please tell if I got something wrong.
I got a few 8-bit ISA modems, most of them are used. Two of them are tested, and turns up to be 56K Modems. Ok.

What modem speeds will work in a xt, a 286 or a 386? The speed of a modem is software-configurated, up to the maximum speed of the perticular modem of course.

I keep those modems just because somebody might want them. Put a post in the "trade/sale" topic then.

I also got several isa sound cards from Creative Labs. What kind?

I was told that the Soundblaster cards were better. Better than What??
Click to expand...
 
The speed of modem is determined by the UART. The XT probably has an 8250, which is limited to 19,200 bps. The '286 & '386 could have one of several UARTs, including 8250, 16450, 16550, etc. With a 16-bit wide UART, you should be able to go up to 56,000 (53,000) bps, if the rest of the computer can handle it. YMMV, of course.

--T
 
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ISA would be internal and the UART would be on the card. I would guess even an XT could deal with a 56K modem full blast.
 
Terry Yager said:
The speed of modem is determined by the UART. The XT probably has an 8250, which is limited to 19,200 bps. The '286 & '386 could have one of several UARTs, including 8250, 16450, 16550, etc. With a 16-bit wide UART, you should be able to go up to 56,000 (53,000) bps, if the rest of the computer can handle it. YMMV, of course.

--T
Click to expand...

i don't think there is any UART built into a standard XT motherboard. the UART for serial ports is on the actual expansion cards where the port connects. same with a modem, the UART is on the card thus any 8-bit ISA modem including a 56K (have they ever even made an 8-bit 56K?) will operate at it's full speed even in an XT.

even if there was a UART for an on-board serial port on the motherboard of an 8-bit bus 8088 computer, it wouldn't affect what's on the modem. it would use it's own UART.

somebody let me know if i'm wrong.
 
> "... the UART for serial ports is on the actual expansion cards where the port connects."

That's why internal modems are generally better on older machines - if you're looking for speed, that is. You aren't limited to the UART on the serial board. Of course, as everyone knows here, running vintage hardware has it's own charms.

That reminds me. One time when trying to sort out some old modems, I came across one 1200 baud card which I couldn't seem to get to work. Until I discovered that it would only take commands in upper case!
 
Terry Yager said:
Yeah, that's what I meant. Are there any 8-bit ISA cards with 16550s?

--T
Click to expand...

Even if there aren't, it's easy enough to replace an 8250 with a 16550--they're pin-compatible.

The big question, however, is what you're doing with the data and how much there is. If you're displaying it on the screen, there's no way an XT will be able to scroll and keep up at 56K--9600 is a real stretch and an XT will fall behind even then if the transmission block size is too large.
 
There's somethng wrong in this thread but I can't put my finger on it.
I would have echo'd Terry's explanation.

In most early computers communication with another device was thru a serial port whether synchronised or unsynchronised, Serial as opposed to parallel. I don't know what chip was used for synchronised data Mo(dulators)/Dem(odulators) but for RS-232 output the chip used was an 8250. Many XTs had serial ports.

My early experence was with Atari STs and BBS' or Freenets. 19,200 BPM was a major hindrance on that platform. Perhaps that is coloring my view, but later I remember favoring one PS-2 m.70(?) for it's faster UART.

I had always used external modems on my Intel machines and wonder why anyone would buy serial cards when a modem card could replace the cost of both a serial card and modem ? Or is my befuddled brain missing something here. Software Modems were always considered inferor tho cheaper so perhaps that's where I'm befuddled.

Lawrence
 
>Micom 2000: "I had always used external modems on my Intel machines and wonder why anyone would buy serial cards when a modem card could replace the cost of both a serial card and modem ?"

Correct me if I'm wrong, but your mean "internal modems" don't you? When you use an internal modem you don't need a seperate serial port and thus are not limited by it's UART since the modem card will have it's own UART of the appropiate speed. Thus you only need one device and not two. With an external modem you need two devices - a serial card and the modem.

Regarding the UART numbers. The older '450 had no FIFO. The '550 had a FIFO but it was faulty and could not be used. The '550a had a working FIFO. AFAIK most people, when they say 16550 are really refering to the '550a but I've heard that some manufacturers refused to use the "a" designation regardless.

- 8250, 16450, early 16550: Obsolete with 1-byte buffers
- 16550, 16550A, 16C552: 16-byte buffers; 115.2 kbps standard, many support 230.4 or 460.8 kbps
- 16650: 32-byte buffers; 460.8 kbps
 
Ole Juul said:
Correct me if I'm wrong, but your mean "internal modems" don't you? When you use an internal modem you don't need a seperate serial port and thus are not limited by it's UART since the modem card will have it's own UART of the appropiate speed.
Click to expand...

There were a number of older (5150-era) internal 8-bit modems that used an 8250 on-board. That's what I thought folks were talking about.
 
Micom 2000 said:
I had always used external modems on my Intel machines and wonder why anyone would buy serial cards when a modem card could replace the cost of both a serial card and modem ? Or is my befuddled brain missing something here. Software Modems were always considered inferor tho cheaper so perhaps that's where I'm befuddled.
Lawrence
Click to expand...

My experience (from many years ago) has been that high-end modems were almost always available only as external devices. I've got a couple of ISA modems (both Winmodem and non-software), but I don't think I've ever used them.

Were there ever any internal modems that could do, for example, bisync, HDLC or any of the non-brain-dead protocols?

Something itching in the back of my skull also says that in an apples-to-apples comparison between the internal and external varieties of the same modem, the external would usually outperform the internal. I can't put my finger on a study that says as much, however.
 
re

re

This is 56k usr isa modem it recognized fine in windows.

As a person who gets a few computers here in buffalo ny.

I find most of my machines being sit out for trash.

Most of the isa cards i find are 16 bit. Full isa cards.

Im to point where i dont even use a floppy drive. I do keep

3 1/2 floppy drives I have requests for them.

One guy contacted me about his floppy drive being dead.

I keep these parts only because I never know when someone might need

them. Isa video cards for example on ebay the sellers think they have gold

20 bucks for an isa card for 7.50 to ship it
 
Chuck(G) said:
Even if there aren't, it's easy enough to replace an 8250 with a 16550--they're pin-compatible.

The big question, however, is what you're doing with the data and how much there is. If you're displaying it on the screen, there's no way an XT will be able to scroll and keep up at 56K--9600 is a real stretch and an XT will fall behind even then if the transmission block size is too large.
Click to expand...

I disagree, only because I've been doing that recently as part of my hobby. I agree with you that it depends on the application, though. If all you're doing is displaying text data in textmode, 56K is easy (remember, the serial communications are on interrupts so there's no worry about losing bits). If you're trying to render an HTML page in graphics mode, then forget it.
 
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