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Fixes for MACHINE_XT build #32

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merged 2 commits into from
Feb 23, 2023
Merged

Fixes for MACHINE_XT build #32

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1878b73
Fix MACHINE_XT PPI switch read, preserve IMR during detect_rom_ext
640-KB Feb 23, 2023
4ddcbc2
MDA video adapter can only be mode 7
640-KB Feb 23, 2023
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7 changes: 5 additions & 2 deletions bios.asm
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Original file line number Diff line number Diff line change
Expand Up @@ -1001,7 +1001,7 @@ low_ram_ok:
and al,0FDh ; clear switch select bit - select SW5-SW8
%endif ; MACHINE_FE2010A
%ifdef MACHINE_XT
and al,0F7h ; clear switch select bit - select SW5-SW8
or al,08h ; set switch select bit - select SW5-SW8
%endif ; MACHINE_XT
out ppi_pb_reg,al
in al,ppi_pc_reg ; read switches SW5-SW8
Expand Down Expand Up @@ -1281,7 +1281,8 @@ config_table:
detect_rom_ext:
mov al,e_ext_start ; ROM extension scan start
out post_reg,al

in al,pic1_reg1 ; get IMR (option ROMs may trash it)
push ax ; save it
mov dx,0C800h
mov bx,0F800h
%ifdef AT_RTC_NVRAM or FLASH_NVRAM
Expand Down Expand Up @@ -1315,6 +1316,8 @@ detect_rom_ext:
jmp .ext_scan_loop

.ext_scan_done:
pop ax ; get previous IMR
out pic1_reg1,al ; restore it
mov al,e_ext_complete ; ROM extension scan complete
out post_reg,al

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9 changes: 6 additions & 3 deletions video.inc
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Expand Up @@ -200,13 +200,16 @@ int_10_fn00:
; assume CGA mode
mov cx,0B800h ; CGA video memory segment
mov dx,3D4h ; port for MC6845 CRTC address register
mov al,byte [equipment_list] ; get equipment - low byte
and al,equip_video ; get video adapter type
cmp al,equip_mono ; monochrome?
mov al,0
cmp bl,07h
jb .color ; jump if CGA/color mode
jne .color ; jump if CGA/color mode
; set MDA mode
mov bl,07h ; MDA can only be 7
mov ch,0B0h ; MDA video memory segment
mov dl,0B4h ; port for MC6845 CRTC address register
inc al
inc ax
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saves 1 byte :)


.color:
mov es,cx ; ES = video memory segment
Expand Down