On Sat, 16 Dec 2000 07:36:29 -0500 (EST), [EMAIL PROTECTED] (Howard Eisenberger)
wrote:
> "J. J. Young" <[EMAIL PROTECTED]> wrote:
>> Has anyone tried a parallel port modem? -- or even seen one?
> Yes. I have used a Xircon parallel port 14.4 pocket modem on my
> 386sx16 laptop. It came with software (port redirector) for DOS
> and Win3.x only. The software is compatible with QEMM, but not
> himem.sys or emm386.
> I was able to run DOS PPP applications, including early versions
> of Arachne, using the Merit packet driver (etherppp), but I could
> not get dospppd or Klos to work.
> The unit (about the size of a mouse) is a modem/NIC combo, but I
> didn't try the NIC. I still have it stashed away (along with the
> laptop), but haven't played with it for some time. I was planning
> to reinstall Minix, and I know that any software modem is useless.
> Unfortunately, there are 8250 UARTs on the laptop, which would
> likely be a problem for a real modem (>9600?).
> Howard E.
Dear Howard E.
James Fuller here. I have a suggestion for you re the ubiquitous 8250
UART. Point the first : 8250 UART cannot handle some operations
corectly, this was corrected in the 8250B chip. Neither is capable of
high baud rates.
If the 8250 in your laptop turns out to be a standard 40 pin chip, you
can simply remove it and insert a 16550 chip DIRECTLY in its place with
no other alterations.
How to tell : The chip has a 1.9" by 0.6" pin outline.
How to do : Cut the leads against the actual chip with good small
sidecutters. Remove the pins individually by desoldering. This method
removes the risk to the PCB of your machine, which is literally the MOST
IMPORTANT PART of it. Then, if there is room for the new chip to be
fitted into a socket, use one. Otherwise, solder the new chip directly
into the socket.
General points.
Often in adapter cards, the UARTs and Parallel ports are included in an
LSI chip smaller than a postage stamp, with myriad connections. Forget
it, it cannot be done with this sort of chip. I believe these chips were
often 16451 and 16452 (1 and 2 serial ports respectively). Because of
manufacturers cloning devices, look for the last 3 digits in the name,
as the 'prefix' is often altered drastically.
Getting the part number off a chip is a minor skill in itself. Do not
confuse it with the 'date code', which is of the form 'yyww', where the
'yy' component is the year, and the 'ww' component is the week in the
year. eg, 9123 means the 23rd week in 1991.
> --
> DOS TCP/IP * <URL:http://www.ncf.ca/~ag221/dosppp.html>
http://www.nimnet.asn.au/~kali
