UART at 8250 instead of 16550?

[bill1971]

Built 2 identical systems for a friend and his son who live a half a
block from each other. Both using Actiontec 56K PC Lite modems.
One machine is doing fine at UART 16550, while the other is not,
and registers at only 8250. How do I change this on the machine
in question? Thanks.

- Bill

[jmichna]

Bill,
It's been a while since I've messed with modems, and its beeen awhile since any modems have not come with UART 16550, at least five years (My Zoom 28.8 was 16550). I seem to recall there was an AT command that would verify modem configuration, and also allow the user to change and save modem configuration. Have you checked the AT command set literature (that hopefully came with the modems)? I think I used to go thru a litany of ATI0, ATI1, ATI2, etc. while in terminal mode.

I guess what I'm saying is "are you sure that the second modem is really only functioning as an 8250?"

Do you see any difference in d/l and u/l speeds? What OS is installed on these two pcs?
jmichna

[bill1971]

j:
I'll research this a little more. Both machines are running
Win98SE. Thanks for your input.

AT&T Worldnet told my friend that the 8250 was the reason he
could not connect thru the local access no. (This was not originally a problem, because he used to connect with the alternate access no.,but now, AT&T has discontinued that 2nd number, and he's stuck with trying to connect with that first troublesome one).
Seems like if one local access no. connected, why wouldn't the
other?

Thanks again for any help.

- Bill

[Buji]

Modem Properties|General,Maximum Speed and Connection|Port Settings. You should also change the port speed by editing the Port lines in the Win.ini file from 9600,n,8,1,x to 115200,n,8,1,x Don't know if there is any truth to it, I've done it and not noticed any change.
http://www.56k.com/trouble/connect.shtml

[Psycho Logical]

The numbers 8250 and 16550 are types of UART hardware chips, not software settings or modes that you can change on any one particular chip or modem.

The 8250 is older technology, with one input register that holds only one byte at a time. These UARTs are not usually suitable for modem speeds greater than 9600 bits per second (BPS) because of possible input data overruns that can occur if a character is left in the input register when the next byte is received.

The newer 16550 UART allows data transfer at high speeds with a 16-byte first in, first out (FIFO) input register. The FIFO feature can buffer up to 16 bytes at a time, preventing data overruns in applications that are 16550 aware.

The 16550 UART can be forced into 8250 compatibility mode if you are running older software that is not 16550 aware. Windows itself since Win95 is capable of supporting 16550 features.

I'd say you have one older and one newer model modem. If they have the same model number, then Actiontec made a switch in production without updating the number. You should be able to see the number printed on the UART chip itself, although it may be shortened to "250" or "6550" or even combined as part of a longer number.

[michaeln]

Originally posted by Psycho Logical
I'd say you have one older and one newer model modem. If they have the same model number, then Actiontec made a switch in production without updating the number. You should be able to see the number printed on the UART chip itself, although it may be shortened to "250" or "6550" or even combined as part of a longer number.

The UART Chip is usually on the mobo (Com Port) not on the modem

[bluemoon]

I say both mobo as well as the "internal modem" have Uart chips.

bluemoon

[philocipher]

IF its the same type of modem it should be same uart

besides uarts slower then 16650 haven't been seen in modems for a long time
so it must be something else.. try dialing into another ISP if u get anything higher then or equal to 36000 then you should call at&t again and talk to the supervisor