Black Box MD1640A, MD1641A manual File Transfer Is Slower Than It Should Be, Am Losing Data

APPENDIX A: Troubleshooting

File Transfer Is Slower Than It Should Be

•You may have an older UART. For best throughput, install a 16550AFN UART. See the “Quick Start” chapter for information on how to identify your UART.

•If you are running under Windows 3.1 and have a 16550AFN UART, you must replace the Windows serial driver, COMM.DRV, to take full advantage of the UART’s speed.

•If you are using a slow transfer protocol, such as Xmodem or Ker- mit, try Zmodem or Ymodem/G instead.

•Is your line noisy? If there is static on your line, the modem has to re-send many blocks of data to insure accuracy. You must have a clean line for maximum speed.

•Are you downloading a compressed file with MNP 5 hardware com- pression enabled? Since hardware data compression cannot com- press a file already compressed by an archiving program, the transfer can be marginally slower with data compression enabled than with it disabled.

•Try entering the L8 (List Online Diagnostics) command in on-line mode, making a screen print of the diagnostics listing, and checking for parameters that may be unacceptable (number of re- trains, round trip delay, etc.).

I Am Losing Data

•If you are using data compression and a high speed serial port, set the serial port baud rate to four times the data rate.

•Your UART may not be reliable at serial port speeds over 9600 bps or 19,200 bps. Turn off data compression, reset your serial port speed to a lower rate, or replace your serial port with a faster one.

•Make sure the flow control method you selected in software match- es the method selected in the modem. If you have a Macintosh, you may have the wrong cable for hardware flow control.

•If you are running under Windows 3.1 and have a 16550AFN UART, you may need to turn on the 16550’s data buffers and/or replace the Windows serial driver, COMM.DRV.

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