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Time Division Processing
Overview
MFM has developed a new software-based solution to lost data errors. MFM calls this Time Division Processing (TDP). TDP improves data reliability by up to 80% on computers experiencing lost data errors in PC Access for Windows. This technology reduces the interference other Windows processes (e.g. print spooling, print rendering etc.) have on incoming data from the serial port.
- TDP is available as an optional setup item starting in Build 94 of PC Access for Windows version 4.00.
- TDP should be useful primarily to users running Windows 3.1 and Windows 3.11 for Workgroups. (Serial communication under Windows 95 is usually much more reliable.)
- You should try TDP if you have tried the other options in the Fixing Communication Errors and continue to have lost data errors.
Details
TDP increases reliability of serial communication by limiting the interaction of other Windows processes with the incoming serial data. TDP generally reduces PC Access for Windows performance by 10-15% on a given task, but increases reliability 70-100% for nearly error free communications.TDP requires hardware flow control between the modem and the computer. Therefore proper cables and modem configurations are necessary for TDP to function properly.
To enable the TDP option, select the Time Div/Hardwr radio button in the Flow Control group in the MLS Setup and Add/Edit Phone Book Entry windows. The TDP radio button replaces the Fast Hardware radio button which appeared in build 93 and earlier builds of PC Access for Windows. Users who previously selected Fast Hardware will revert to standard Hardware flow control. This is not a problem since there was no difference between the two options anyway.
The default time division is 55 milliseconds. You can change
this value in the Time Division Window field on
the advanced version of the Modem Setup
window. MFM recommends values in the range 55 - 165
milliseconds. Setting the time division to zero completely disables
the TDP option even if you select the Time Div/Hardwr
radio button in the Flow Control group on the
MLS Setup or Add/Edit Phone Book
Entry windows.
When using TDP, you should double your Speed setting
for initial testing. (The Speed radio button group
appears on the
MLS Setup and Add/Edit Phone Book
Entry windows.
This maximizes performance of PC Access for Windows.
If you still get communication errors with TDP enabled, try
reducing your Speed to the next lowest setting.
This should fix the problem on even the most troublesome computers.
During an online session with TDP active, you will notice
"blocky" display updating. There may be a slight time delay
between typing and seeing the result on the screen. Increasing the
Time Division Window setting will worsen this
"turn around" delay but will also improve
throughput and performance. Setting the value above 200 milliseconds
will not improve performance and is not advisable.
Compatibility and Testing
TDP has worked well with a number of modem brands and computers.
However, given the astronomical number of possible combinations of
computer hardware and system software, MFM cannot guarantee
that TDP will operate correctly in all environments. TDP
has not yet increased communication reliability under Windows 95.