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From: alex@umbc4.umbc.edu (Alex S. Crain)
Newsgroups: comp.sys.3b1,comp.sys.ibm.pc.hardware
Subject: AT clone <-rs232-> 3b1 problems
Keywords: a real stumper.
Message-ID: <1991Jun14.161117.25908@umbc3.umbc.edu>
Date: 14 Jun 91 16:11:17 GMT
Sender: newspost@umbc3.umbc.edu (News  posting account)
Organization: University of Maryland Baltimore County
Lines: 58


	Hey kids!

	I've been trying to set up a seial link between my at&t 3b1 and
an Everex AT clone (model 18001) and I'm having trouble.

	hardware:
		at&t 3b1, using the stock serial port
		Everex 18001 with no-name serial card at com1 (8250 driver)
		Opus PM110 unix coprocessor (optional)

	Software:
		kermit/unix3.51 <-> kermit/dos3.31 (no opus card)
		uucp/unix3.51 <-> uucp/Sys5r3/dos3.31

	symptoms:
		The machines connect and pass data for ~20 minutes, at
		which time the serial card on the AT loses its mind and
		starts dropping lots of characters (like half). The	
		system must be rebooted before the card can recover.

	I've tried (without any noticable effect):
		Every flavor of DTE/DTE cable I can think of.
		Different serial cards, including an Everex EV-170.
		Taking everything out of the PC except the disk, serial port.
		forcing kermit to use Xon/xoff flow control
		toggling hardware flow control on the 3b1
		using different flavors of DOS: IBM 3.31, Microsoft 3.31,
			Microsoft 4.1
		Different clock speeds on the AT (8mhz, 10mhz)
		Different flavors of flow control in the Opus tty driver.
	
	With marginal effect:
		Different baud rates: 9600,4800,2400. Slower baud rates
			take longer to trash the card, but it still happens.

	Notes:
		I don't suspect the 3b1. This machine handles uucp traffic
			daily without problems.
		I successfully transferred several megabytes between the
			3b1 and an at&t 6300 without a hitch.
		I tried swapping the PC for another Everex unit, no change.
		The data transferred seems to be irrellevent.
		Using kermit, I can get ~8000 packets. This can be one big
			file or several small ones, but it always dies 
			between ~8000 and ~8500 packets (9600 baud). It
			never dies on the same packet twice.
		Similarly, using uucp, I always get about 800K bytes, one
			or multiple files, it doesn't matter.

	I'm completely at a loss. My workaround is to send 500K and reboot
	the machine, but I'm open to other suggestions.

-- 
#################################		           :alex.
#Disclaimer: Anyone who agrees  #                 Systems Programmer
#with me deserves what they get.#    University of Maryland Baltimore County
#################################	    alex@umbc3.umbc.edu