Browse Prior Art Database

Fast Path Data Transfer Interface

IP.com Disclosure Number: IPCOM000061027D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 62K

Publishing Venue

IBM

Related People

Hansen, BW: AUTHOR [+3]

Abstract

A method is provided to improve the data transfer performance between PC (personal computer) applications and twinax-connected host systems. This support is part of the IBM 5250 Enhanced Emulation package. The 5250 Enhanced Emulation installs itself as part of the IBM PC operating system with a twinax connection to an IBM S/36 or S/38. It filters all user input and redirects the PC keystrokes as 5250 scan codes to the host system via the twinax line. The emulated host workstation screen is a buffer maintained in PC RAM (random-access memory). A performance goal of the Fast Path method is to achieve the rate of a PC diskette. The main obstacle to achieving bulk data thruput is the fact that the host system views the twinax-connected PC as a "dumb" terminal.

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Fast Path Data Transfer Interface

A method is provided to improve the data transfer performance between PC (personal computer) applications and twinax-connected host systems. This support is part of the IBM 5250 Enhanced Emulation package. The 5250 Enhanced Emulation installs itself as part of the IBM PC operating system with a twinax connection to an IBM S/36 or S/38. It filters all user input and redirects the PC keystrokes as 5250 scan codes to the host system via the twinax line. The emulated host workstation screen is a buffer maintained in PC RAM (random-access memory). A performance goal of the Fast Path method is to achieve the rate of a PC diskette. The main obstacle to achieving bulk data thruput is the fact that the host system views the twinax-connected PC as a "dumb" terminal. The only available data transfer mechanism is via the display screen buffer. Prior to the Fast Path method, a PC application would basically emulate an operator filling the screen with data and pressing Enter to send the information. A screen-handling application on the host would save the data to a file and reset the keyboard to allow further input. The PC application would then refill the buffer and send another Enter key. This cycle would continue until all data transferred. To receive data, the host application filled the buffer, and the PC application copied it. The Fast Path transfer method sends the Enter key scan code to initiate a transfer, with all synchronization of copying and refreshing the screen buffer handled at the twinax level when responding to specific Work Station Controller (WSC) commands, as in Fig. 1. The Fast Path interface specifically uses the Post Activate and Write Data Load Cursor commands. The Post Activate command follows completion of a Read or Write Activate command that requests transfer of a block of screen data from the PC screen buffer. The Write Data Load Cursor command is issued following successful completion of the transfer of an entire screen frame. This command is issued at the earliest possible point at which the screen buffer in RAM may be read or refreshed for the next host interaction. Fast Path has three distinct layers of processing.
1.Main Level Code (no interrupts being serviced) This routine runs on the main level and is called by the PC application requesting a data transfer. This routine sets a variable flag to indicate a Fast Path transfer and the requested direction of that transfer. It fills the screen buffer, if necessary, and initiates the process by sending an Enter scan code. This routine then waits for the Fast Path variable flag to be reset, indicating the end of the transfer, before returning control to the calling application. 2. Post Activate Recovery Interrupt Th...