Mode X.. plus some!
29 Nov 2012So, not much of tutorial here - just a neat layout of setup code for a few mode X modes I’ve come across now and then.
First of all, just some formalities. Setting Mode X tweaks to the VGA is a massive port-out exercise. Creating the following macro cut down on my code heaps.
outp MACRO port, value
mov dx, port
mov al, value
out dx, al
ENDMSo you can see, it just gives sending a byte out to a port a bit of syntactical sugar in assembly language. Easy.
The only other piece of formality is, you must have set the video display into MCGA (mode 13) first:
set_mcga:
mov ax, 0013h
int 10h
retOn to the modes.
tweak_160x120:
; --------------------------
; 160x120
;
; pages = 13
; line size = 40
; page size = 19200
; --------------------------
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 07fh
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
outp 03c2h, 0e3h
outp 03d4h, 000h
outp 03d5h, 032h
outp 03d4h, 001h
outp 03d5h, 027h
outp 03d4h, 002h
outp 03d5h, 028h
outp 03d4h, 003h
outp 03d5h, 020h
outp 03d4h, 004h
outp 03d5h, 02bh
outp 03d4h, 005h
outp 03d5h, 070h
outp 03d4h, 006h
outp 03d5h, 00dh
outp 03d4h, 007h
outp 03d5h, 03eh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 043h
outp 03d4h, 010h
outp 03d5h, 0eah
outp 03d4h, 011h
outp 03d5h, 0ach
outp 03d4h, 012h
outp 03d5h, 0dfh
outp 03d4h, 013h
outp 03d5h, 014h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 0e7h
outp 03d4h, 016h
outp 03d5h, 006h
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 003h
outp 03c5h, 000h
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 011h or 020h
outp 03c0h, 0
mov dx, 03dah
in al, dx
outp 03c0h, 012h or 020h
outp 03c0h, 0fh
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
mov dx, 03dah
in al, dx
outp 03c0h, 014h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 80h
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
ret
tweak_296x220:
; --------------------------
; 296x220
;
; pages = 4
; line size = 74
; page size = 65120
; --------------------------
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 7fh
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
outp 03c2h, 0e3h
outp 03d4h, 000h
outp 03d5h, 05fh
outp 03d4h, 001h
outp 03d5h, 049h
outp 03d4h, 002h
outp 03d5h, 050h
outp 03d4h, 003h
outp 03d5h, 082h
outp 03d4h, 004h
outp 03d5h, 053h
outp 03d4h, 005h
outp 03d5h, 080h
outp 03d4h, 006h
outp 03d5h, 00dh
outp 03d4h, 007h
outp 03d5h, 03eh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 041h
outp 03d4h, 010h
outp 03d5h, 0d7h
outp 03d4h, 011h
outp 03d5h, 0ach
outp 03d4h, 012h
outp 03d5h, 0b7h
outp 03d4h, 013h
outp 03d5h, 025h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 0e7h
outp 03d4h, 016h
outp 03d5h, 006h
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 80h
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
ret
tweak_320x200:
; --------------------------
; 320x200
;
; pages = 4
; line size = 80
; page size = 64000
; --------------------------
outp 03c4h, 04h
outp 03c5h, 06h
outp 03d4h, 017h
outp 03d5h, 0E3h
outp 03d4h, 014h
outp 03d5h, 0
ret
tweak_320x240:
; --------------------------
; 320x240
;
; pages = 3
; line size = 80
; page size = 76800
; --------------------------
outp 03d4h, 11h
mov dx, 03d5h
in al, dx
and al, 7fh
mov bl, al
outp 03d4h, 11h
outp 03d5h, bl
outp 03c2h, 0e3h
outp 03d4h, 000h
outp 03d5h, 05fh
outp 03d4h, 001h
outp 03d5h, 04fh
outp 03d4h, 002h
outp 03d5h, 050h
outp 03d4h, 003h
outp 03d5h, 082h
outp 03d4h, 004h
outp 03d5h, 054h
outp 03d4h, 005h
outp 03d5h, 080h
outp 03d4h, 006h
outp 03d5h, 00dh
outp 03d4h, 007h
outp 03d5h, 03eh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 041h
outp 03d4h, 010h
outp 03d5h, 0eah
outp 03d4h, 011h
outp 03d5h, 0ach
outp 03d4h, 012h
outp 03d5h, 0dfh
outp 03d4h, 013h
outp 03d5h, 028h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 0e7h
outp 03d4h, 016h
outp 03d5h, 006h
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
or al, 80h
mov bl, al
outp 03d4h, 11h
outp 03d5h, bl
ret
tweak_320x400:
; --------------------------
; 320x400
;
; pages = 2
; line size = 80
; page size = 128000
; --------------------------
outp 03c4h, 004h
outp 03c5h, 006h
outp 03d4h, 017h
outp 03d5h, 0E3h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 040h
ret
tweak_360x360:
; --------------------------
; 360x360
;
; pages = 2
; line size = 90
; page size = 129600
; --------------------------
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 7fh
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
outp 03c2h, 067h
outp 03d4h, 000h
outp 03d5h, 06bh
outp 03d4h, 001h
outp 03d5h, 059h
outp 03d4h, 002h
outp 03d5h, 05ah
outp 03d4h, 003h
outp 03d5h, 08eh
outp 03d4h, 004h
outp 03d5h, 05eh
outp 03d4h, 005h
outp 03d5h, 08ah
outp 03d4h, 006h
outp 03d5h, 0bfh
outp 03d4h, 007h
outp 03d5h, 01fh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 040h
outp 03d4h, 010h
outp 03d5h, 088h
outp 03d4h, 011h
outp 03d5h, 085h
outp 03d4h, 012h
outp 03d5h, 067h
outp 03d4h, 013h
outp 03d5h, 02dh
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 06dh
outp 03d4h, 016h
outp 03d5h, 0bah
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
or al, 80h
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
ret
tweak_400x300:
; --------------------------
; 400x300
;
; pages = 2
; line size = 100
; page size = 120000
; --------------------------
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
and al, 7fh
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
outp 03c2h, 0e7h
outp 03d4h, 000h
outp 03d5h, 071h
outp 03d4h, 001h
outp 03d5h, 063h
outp 03d4h, 002h
outp 03d5h, 064h
outp 03d4h, 003h
outp 03d5h, 092h
outp 03d4h, 004h
outp 03d5h, 067h
outp 03d4h, 005h
outp 03d5h, 082h
outp 03d4h, 006h
outp 03d5h, 046h
outp 03d4h, 007h
outp 03d5h, 01fh
outp 03d4h, 008h
outp 03d5h, 000h
outp 03d4h, 009h
outp 03d5h, 040h
outp 03d4h, 010h
outp 03d5h, 031h
outp 03d4h, 011h
outp 03d5h, 080h
outp 03d4h, 012h
outp 03d5h, 02bh
outp 03d4h, 013h
outp 03d5h, 032h
outp 03d4h, 014h
outp 03d5h, 000h
outp 03d4h, 015h
outp 03d5h, 02fh
outp 03d4h, 016h
outp 03d5h, 044h
outp 03d4h, 017h
outp 03d5h, 0e3h
outp 03c4h, 001h
outp 03c5h, 001h
outp 03c4h, 002h
outp 03c5h, 00fh
outp 03c4h, 004h
outp 03c5h, 006h
outp 03ceh, 005h
outp 03cfh, 040h
outp 03ceh, 006h
outp 03cfh, 005h
mov dx, 03dah
in al, dx
outp 03c0h, 010h or 020h
outp 03c0h, 041h
mov dx, 03dah
in al, dx
outp 03c0h, 013h or 020h
outp 03c0h, 0
outp 03d4h, 011h
mov dx, 03d5h
in al, dx
or al, 80h
mov bl, al
outp 03d4h, 011h
outp 03d5h, bl
retI will have an update to this post. There are some nuances that I’d much prefer explain to you with a couple of nice code blocks rather than how I’m just going to throw it into the page.
These chunks will be helpful in page selection and optimizing page draws to multiple pages at once.
; setting a page
; activeOffset = vgapage + (page * pageSize / 4);
; enable all planes
; outp 03c4h, 02h
; outp 03c5h, 0fhSome really good references on this topic are
Well, that’s it for now.