TBBS 2.x - TBBS and Emulated or Simulated EMS (LIMSIM)

Contact:   eSoft, Inc. (Makers of TBBS)
           15200 E. Girard Ave., Suite 3000
           Aurora, CO  80014
           (303) 699-6565      Voice
           (303) 699-6872      Fax
           (303) 699-8222      BBS
           support@esoft.com   E-Mail

TBBS AND EMULATED OR SIMULATED EMS (LIMSIM)
-------------------------------------------

In certain circumstances, TBBS may require EMS (expanded, LIM 3.2 or 4.0 
memory).  On XT-class (8088/8086) based computers, and AT-class (80286) based 
computers, this usually means purchasing an EMS expansion card, such as the 
Intel Above Board or AST Six-Pack.  

Some XT- and many AT-class machines have more than 640k of memory installed.  
This memory is usually extended memory (versus expanded) and CANNOT be used by 
TBBS.  Because the method used to access extended memory is necessarily slow, 
you SHOULD NOT use this memory for other purposes (such as a RAM disk or hard 
disk cache) while TBBS is running, or you may seriously impact the performance 
of your system.

Essentially, extended memory XT- and AT-class machines is USELESS in a TBBS 
environment. 

You may encounter special software drivers that claim to take your extended 
memory and make it into expanded.  Some of these programs even claim to use 
your hard disk to emulate expanded memory.  THESE SCHEMES CANNOT AND DO NOT 
WORK IN A TBBS ENVIRONMENT!  The access to this emulated EMS memory if far too 
slow for use with TBBS.  These schemes are sometimes called "LIMSIM" since 
they simulate LIM (EMS) memory. 

EMS is paged memory, meaning that there is a memory "window" where DOS can 
access it, and the EMS memory is paged in and out of this window by the 
program (TBBS in this case) when a particular area in EMS memory is needed. 

The speed at which this paging takes place is critical to the performance of 
TBBS.  The program requires a page switching speed of better than 200 
microseconds.  If the memory pages happen any slower, performance will be 
seriously affected, and TBBS may in fact become totally unusable. 

A program included with TBBS, called EMSTEST, will report the page switching 
speed of your EMS to you.  If the page switching speed is greater than 200 
microseconds, you should not attempt to use the EMS technique you currently 
have in a TBBS environment. 

NOTE:  Programs specifically designed for 80386, 80486 and Pentium based 
machines that remap extended memory into expanded memory ARE okay for use with 
TBBS.  The memory architecture of these microprocessors allows this remapping 
to occur in an efficient manner.  Such programs include QEMM, 386MAX and CEMM. 

- END -
TBBS0014
Rev. 10/90

Revised 10/93
Copyright (C) 1994 eSoft, Inc., All Rights Reserved.  Permission granted
to distribute this file in its entirety, without modification, to any
interested party.  Any other use requires the written permission of
eSoft, Inc.

IMPORTANT:  The information herein is subject to change without notice.
Please call or write to confirm factual information of importance to you
or your organization.

