    AST RESEARCH, INC.        TECHNICAL BULLETIN # 1536           7-19-96

    TITLE: Ascentia J Modem Error Correction

    SUMMARY

       The integrated modem in the Ascentia J is not capable of performing
       hardware error correction and data compression.

       This issue affects all Ascentia J systems.

    ISSUE

       The integrated modem in the Ascentia J is not capable of performing
       hardware error correction and data compression.  This can result in
       garbled data and intermittent broken connections with other systems.

    BACKGROUND

       Rockwell Protocol Interface (RPI(TM)) is a technology that allows
       the PC host computer to perform error correction and data
       compression (ECC) technologies. Traditionally, this occurred
       in the modem hardware.

       RPI is an asynchronous HDLC (High Level Data Link Control) link
       that operates between a PC and a modem, allowing data compression
       and error correction to take place on the host PC.  This allows RPI
       to operate using standard PC COM ports, or standard serial cards.
       The V.42bis bit stream presented to the remote modem from an RPI
       modem looks exactly like that which would come out of a traditional
       hardware implementation of V.42bis, fully synchronous and full
       duplex.  MNP levels 2,3,4,5 are supported as well as V.42 LAP-M,
       and V.42bis.

       To get ECC with RPI, as one would get using a hardware
       implementation of ECC, the PC communications application needs
       either a driver or a software package that supports RPI; the modem
       itself needs firmware that supports RPI.

       One benefit of RPI is that it lowers the interrupt rate to the
       operating system (OS), as only precompressed data is sent on the
       COM port, unlike hardware ECC modems, which send uncompressed data
       over the serial port.  If the data is compressible at a ratio of
       2 to 1, which is very likely with ASCII text, then an RPI modem
       interrupts the OS approximately 50% less than a hardware ECC modem
       would.

       The Ascentia J integrated modem uses the Rockwell RC144ATF
       chipset with firmware 2.20, which provides support for RPI.

    ACTION

       For Windows 95, download filename 95RPI115.EXE from one of AST's
       On-Line! services.

       For Windows 3.1x, download filename WRPI_226.EXE from one of AST's
       On-Line! services.

       Extract the file onto a floppy disk, and follow directions in the
       README.TXT file.

       You can download the files mentioned above from the following
       services:

       AST WWW Site:  http://www.ast.com
       AST On-Line! BBS*:  See IB0001.TXT
       CompuServe:  GO: ASTFORUM
       Prodigy: Jump: astsupport

       * Refer to IB0001.TXT for a list of AST's international BBS
         numbers.

       To decompress this file, create a temporary directory on your
       hard drive, copy the downloaded file to that directory, and run
       the file.

    NOTES

       The WinRPI driver takes up less than 100KB of system memory.

       Obtain further information on Rockwell WinRPI from the following:

           http://www.nb.rockwell.com/mcd/bman/rpi_faq.html

       See the "WinRPI95 Throughput & Loading" White Paper at

           http://www.nb.rockwell.com/ref/rpi/WinRPI_PC_Loading.html

       for some performance comparison examples.

    TAN 002600GW

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