140 lines
3.3 KiB
NASM
140 lines
3.3 KiB
NASM
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PAGE ,132
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TITLE DXEMM2.ASM -- Dos Extender MEMM Enable Code
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; Copyright (c) Microsoft Corporation 1989-1991. All Rights Reserved.
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;***********************************************************************
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;
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; DXEMM2.ASM -- Dos Extender MEMM Enable Code
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;
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;-----------------------------------------------------------------------
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;
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; This module provides routines that attempt to enable MEMM/CEMM/EMM386
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; drivers. DOSX tries to disable MEMM when starting up, and enables MEMM
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; when terminating.
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;
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; NOTE: This code is in a seperate file from the disable logic because
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; the disable code is discarded after initialization.
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;
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;-----------------------------------------------------------------------
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;
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; 12/08/89 jimmat Finally got around to implementing this.
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;
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;***********************************************************************
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.286p
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; -------------------------------------------------------
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; INCLUDE FILE DEFINITIONS
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; -------------------------------------------------------
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.xlist
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.sall
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include segdefs.inc
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include gendefs.inc
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.list
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if NOT VCPI
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; -------------------------------------------------------
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; GENERAL SYMBOL DEFINITIONS
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; -------------------------------------------------------
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; -------------------------------------------------------
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; EXTERNAL SYMBOL DEFINITIONS
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; -------------------------------------------------------
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; -------------------------------------------------------
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; DATA SEGMENT DEFINITIONS
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; -------------------------------------------------------
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DXDATA segment
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public fMEMM_Disabled, MEMM_State, MEMM_Call
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fMEMM_Disabled db 0 ; NZ if MEMM disabled
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MEMM_state db 0 ; Initial MEMM state
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MEMM_Call dd 0 ; far call address into EMM driver
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DXDATA ends
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; -------------------------------------------------------
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; CODE SEGMENT VARIABLES
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; -------------------------------------------------------
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DXCODE segment
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DXCODE ends
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DXPMCODE segment
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DXPMCODE ends
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; -------------------------------------------------------
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subttl MEMM/CEMM/EMM386 Enable Routines
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page
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; -------------------------------------------------------
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; MEMM/CEMM/EMM386 ENABLE ROUTINES
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; -------------------------------------------------------
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DXCODE segment
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assume cs:DXCODE
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; -------------------------------------------------------
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; EMMEnable -- This routine attempts to re-enable any installed
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; MEMM/CEMM/EMM386 driver.
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;
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; Input: none
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; Output: CY off - EMM driver enabled (or never disabled)
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; CY set - EMM installed, and can't disable
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; Errors:
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; Uses: All registers preserved
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assume ds:DGROUP,es:NOTHING,ss:NOTHING
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public EMMEnable
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EMMEnable proc near
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push ax
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cmp fMEMM_Disabled,0 ; Did we disable MEMM before?
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jz enable_exit ; no, don't need to enable then
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mov ah,01 ; Set state command
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mov al,MEMM_state ; Get initial state
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cmp al,2 ; They return 0 (on), 1 (off),
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jbe @f ; 2 (auto on), 3 (auto off) -- but
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mov al,2 ; we can only set 1 - 2
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@@:
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call [MEMM_Call] ; and restore it
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jc not_enabled
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mov fMEMM_Disabled,0 ; no longer disabled
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clc
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jmp short enable_exit
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not_enabled:
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stc
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enable_exit:
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pop ax
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ret
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EMMEnable endp
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; -------------------------------------------------------
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DXCODE ends
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;****************************************************************
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endif ; NOT VCPI
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end
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