EXECA20OFF

Purpose:    Sets the lines state "A20" at the start of executing a freshly
            loaded program.

Syntax:     EXECA20OFF = <YES|NO>

By default: EXECA20OFF = YES

Note:
     Everything described below is applicable only when the system is using
the HMA (See the DOS=HIGH command).

     By default, the system tries to make the HMA area invisible before
transferring the control to the loaded program's first instruction,
imitating the address space of 88/86 processor PCs. It is worth mentioning
that some programs designed with old versions of the Microsoft LINK, work
incorrectly if loaded lower than the first 64K of memory. In such cases the
error is unnoticed if the higher 64K of the first megabyte are located below
(XT type). The system automatically fixes the code of such programs (See the
LOADFIX command), but not always, like when, for instance, the "bad"
program is packed with an utility as PKLITE etc. Therefore, if there are no
old programs involved or if the "A20" line is being automatically controlled
by the computer, it is better to set EXECA20OFF = NO, which will slightly
accelerate loading of smaller programs.