Simple and Cheap Solution to RT serial problems

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2 total messages Started by John Wiederhold Sun, 12 Nov 1989 04:31

#546

Author: John Wiederhold
Date: Sun, 12 Nov 1989 04:31

39 lines
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After getting fed up with "device /dev/ttys0 overflow" errors while
I was running at 9600 baud, I realized that there is a reasonably
simple and inexpensive way to fix this.  I got standard IBM serial
card meant for your basic IBM-PC/XT, and replaced the UART chip on
it.  Once installed in the RT, it shows up as ttyc0.  The card costs
about $25-30 and the chip costs about $15.  Now my RT runs at 19200
baud without one complaint.

The details:
The standard IBM serial card for a PC will work in your RT (at least in
my 6150-125), you just have to install it and go to your /dev directory
and do the appropriate MAKEDEV.  This card will give you slightly 
better performance than the built in serial ports (plus they have
standard 25 connectors).  To increase the performance you can replace
the standard UART chip with a National Semiconductor one that
has FIFO (First In First Out) buffers built in.  The UART is a
forty pin chip (I think its the biggest one on the board).  The
standard one is a 8250 and the one you want to replace it with is a
NS1655AN.  I would suggest getting a forty pin chip socket while
you're at it.  They cost less then a dollar and will prevent any damage
to the chip when you try to solder it in.

Once it's all done and installed you RT should run at 19200 without
problems.

Disclaimer: 
I assume no responsibility for any damage done to your system by this
modification and I can't guarantee that it will work for you.  It's up
to you to determine the suitability of the modification to your needs.
As I said my system is an IBM-RT 6150-125 runing AOS4.3.  The change
greatly improved the reliablity and performance of the serial port.  I
basicly use it for kermit connected to a 19200 baud modem, but I would
soon like to get SLIP working.


Good luck.  Feel free to send any questions or comments to me.

John Wiederhold
Stanford Medical School Information Systems Group

Re: Simple and Cheap Solution to RT serial problems

#576

Author: Jacob Parnas
Date: Thu, 16 Nov 1989 09:17

40 lines
2734 bytes

In article <210@med.Stanford.EDU>, johnw@med.Stanford.EDU (John
Wiederhold) writes:
> After getting fed up with "device /dev/ttys0 overflow" errors while
> I was running at 9600 baud, I realized that there is a reasonably
> simple and inexpensive way to fix this.  I got standard IBM serial
> card meant for your basic IBM-PC/XT, and replaced the UART chip on
> it.  Once installed in the RT, it shows up as ttyc0.  The card costs
> about $25-30 and the chip costs about $15.  Now my RT runs at 19200
> baud without one complaint.
> 
> Good luck.  Feel free to send any questions or comments to me.
> 
> John Wiederhold
> Stanford Medical School Information Systems Group

There are two other solutions to serial port problems on 4.3 BSD/RT/AOS.

1.  Get the IBM "Buffered" 4 port adapter.  With the excellent driver that
    Charlie Slater wrote (at IBM PaloAlto), one can run SLIP and UUCP at 19200
    with no problems.  One needs the "Buffered" 4 port card and the new driver.
    The 4 port card is not useable unless one uses both the "Buffered" card
    and the 4 port fix to the December 4.3/AOS release.

2.  Dickens Data Systems did a port of their 8 port card to 4.3/AOS.  It
    can support multiple ports with input of 38400 baud.  The cost is around
    $1600 per 8 port card.

I use the Dickens card in my home RT and get a full newsfeed with a Telebit
T2500 at 19200 baud and use slip at 38400 baud with the Microcom QX/V.32c
modem, often at the same time.  There don't seem to be any problems.

Hope this information is useful to somebody.

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