

        VEMM  V1.02     VLSI LIM 4.0 DRIVER

        SOURCE FILE:
                        VEMM.ASM

        DRIVER OBJECT FILE:
                        VEMM.SYS

        TO INSTALL THE VEMM DRIVER THE CONFIG.SYS FILE MUST INCLUDE:

                DEVICE = d:\path\VEMM.SYS [options]

                where [options] = /B:E000 * TO USED SEGMENT E000 AS WINDOW
                                  /B:D000   TO USED SEGMENT D000 AS WINDOW
                                  /B:C000   TO USED SEGMENT C000 AS WINDOW
                                  /B:B000   TO USED SEGMENT B000 AS WINDOW
                                  /B:A000   TO USED SEGMENT A000 AS WINDOW
   "WINDOWS" DOES NOT SUPPORT >>  /B:????   TO USED SEGMENT CONVENTIONAL
                                            DOS MEMORY (12MHZ CHIP SET)
                                        * DEFAULT
        THE SAMPLE CONFIG.SYS FILE:

                DEVICE=C:VEMM.SYS /B:????


        TEST ROUTINES:
                        EMSTEST.COM
                        MOVETEST.COM

                ARE THE PC MAGAZINE EMS 4.0 TESTS

APPLICATION NOTES:

1)  Use of extended memory

        The EMS driver is designed to use all the available extended
        (above 1MB) memory as the EMS memory page pool. Other drivers
        that use extended memory should be loaded first.

2)  Shadow RAM, extended memory and the VLSI EMS 4.0 driver

        Some confusion about the selection of RAM mapping above 640K
        and the subsequent effects on the EMS driver exists.  The EMS
        Driver uses a 64K byte window in Shadow RAM space as the physical
        page. As shown above, this 64K region is selectable within the
        Shadow RAM space with possible segment starting addresses of A000H,
        B000H, C000H, D000H, or E000H.  It is also possible to place this
        window in conventional memory using B:????, but some applications
        won't operate with this configuration, specifically MICROSOFT
        WINDOWS is known not to function properly.

        In order for the EMS Driver to operate, Shadow RAM must be enabled
        AND the segment selected for the physical window must be available.
        One must take steps to ensure that 64K segment selected for the EMS
        Driver physical window does not conflict with ROM, Video RAM, etc.
        The driver does insure that the selected window is not being used
        to shadow ROM. In this case, it will signal an error and terminate.


        1MB MEMORY MAP
        With this understanding of the EMS Driver and its use of 64K Shadow
        RAM segments, lets examine the possible side effects:

             ---With Shadow RAM disabled
                   This configuration provides 384KB of extended memory for
                   the EMS page pool but does not provide for an EMS window
                   in the A0000h - E0000h area. The only way the driver can
                   used is to specify conventional DOS memory as the window.
                   Again, some application may not run in this mode.

                                ______________ 0
                                | system RAM |
                                | 640 KByte  |
                                |            |
                                |            |
                                |            |
                                |++++++++++++| 640KByte
                                |            |
                                |  ROM       |
                                | 384 Kbyte  |
                                |++++++++++++| 1 Meg
                                |Extended RAM|
                                |   384KB    |
                                |++++++++++++|

             ---With Shadow RAM enabled
                   This configuration provides does provide for an EMS window
                   in the A0000h - E0000h area but there is no extended memory
                   for the EMS page pool. The driver cannot be used in this
                   configuration.

                              0 _____________
                                | system RAM |
                                | 640 KByte  |
                                |            |
                                |            |
                                |            |
                        640Kbyte|++++++++++++|
                                | Shadow RAM |
                                |  384KByte  |
                                |            |
                           1Meg |++++++++++++| 
