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 <A HREF="ftp://ftp.ast.com/P-OTHER/95RPI115.EXE">95RPI115.EXE</A> from one of AST's
   On-Line! services.

   For Windows 3.1x, download filename <A HREF="ftp://ftp.ast.com/P-OTHER/WRPI_226.EXE">WRPI_226.EXE</A> 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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