OAK Technologies. OTI.

   OTI037C has 256K or 512K.
   OTI-067 has 256K or 512K.
   OTI-077 allows 1MB and up to 1024x768 in 256 colors.
   OTI-087 allows 2MB


OAK-037, 067 and 077:

3DEh (R/W):  Index register
bit 0-4  Index to the OAK extended registers at 3DF.
    5-7  (R) Chip version.  0=OAK=037C, 2=OAK-067, 5=OAK-077, 7=OAK-057
Note: Has anyone seen an 057 ????

3DEh index  9h (R/W):

3DEh index 0Ah (R/W):

3DEh index 0Ch (R/W):  CRT Control
bit   3  I/O write test ?

3DEh index 0Dh (R/W):  Misc
bit 2-3  Should be set to enable access to memory above 256k
      4  For 16 color modes should be set to enable access for memory above
         256K
      5  Clock Select bit 2. Bits 0-1 are in 3C2h/3CCh
      6  1MB if set
      7  512K if set, 256 else.

3DEh index 0Eh (R/W):  Backwards Compatability
bit   7  VGA mode if set

3DEh index 11h (R/W):  Segment
bit 0-3  Read Bank no 
    4-7  Write Bank no
Note: This register apparently write only in Oak-037C.

3DEh index 12h (R/W):  Config

3DEh index 14h (R/W):  Overflow
bit   0  Bit 10 of the VTotal Register (3d4h index 6)
      1  Bit 10 of the Vertical Display End Register (3d4h index 12h)
      2  Bit 10 of the Vertical Retrace Start Register (3d4h index 10h).
      3  Bit 16 of the Display Start Address
      7  Set if Interlace is enabled.

3DEh index 15h (R/W):  Hsync/2
bit 0-7  How far into the scanline the odd frame should start in interlaced
         modes. Usually half the VTotal value.

3DEh index 16h (R/W):  Overflow 2                                    (77 only)
bit   3  Bit 17 of the Display Start address
Note: For 256color modes the Display Start Address is in units of 8 bytes,
      rather than 4 bytes.

Bank Switching:

Two banks exist in reg 3DEh index 11h.



OAK-087:

3DEh index  0:
bit   1  Set for OTI-083, Clear for OTI-087

3DEh index  2  (R/W):
bit 1-2  Video Memory. 0=256k, 1=512k, 2=1M, 3=2M

3DEh index  3  (R/W):
bit   5  ?? (Causes vertical stripes)
      7  ?? 

3DEh index  4  (R/W):
bit   2  Set if using Zero Wait States for the VESA Local BUS interface.

3DEh index  6  (R/W):
bit   0  Clock select ??
      2  Clock select ??
      3  Output to RS2 on the DAC. ??
         If set causes 3C6h-3C9h to access the extended registers on the DAC
      4  ?? (Display reset ??)

3DEh index  9  (R/W):
bit   0  Set if 24bit DAC available ?

3DEh index  Bh:
bit   6  Clear if VESA monitor timings (Jumper )
      7  Clear if non-interlaced monitor timings

3DEh index  Dh (R/W):
bit   4  Should be set in 16color modes
      5  Clock Select ??

3DEh index 10h (R/W):


3DEh index 14h (R/W):  
bit   0  ?? (Makes the display "shake")
      2  ??
      3  Bit 16 of the Display Start Address. Note index 17h
      7  Set if the display is interlaced

3DEh index 17h (R/W):
bit 0-2  Display Start Address bit 16-18

3DEh index 18h (R/W):
bit   2  Clock Select??

3DEh index 21h (R/W):
bit 0-1  Clock select ??
      2  Clear in mode 13h, set in all other 256color modes

3DEh index 23h (R/W):  Write Bank Register
bit 0-4  Read Bank in 64k units.

3DEh index 24h (R/W):  Read Bank Register
bit 0-4  Write Bank in 64k units.

Indices 2-6, 9-Bh, Dh, 11h, 13h-15h, 17h-19h, 20-25h, 30h-36h are used by the
 OTI-087.



  ID Oak VGA:

  if testinx2($3DE,$D,$38) then
  begin
    { We have an OAK }
    if testreg2($3DE,$23,$1F) then
      if (rdinx($3DE,0) and 2)=0 then _OAK_087
                                 else _OAK_083
    else
      case inp($3DE) div 32 of
        0:_OAK_037C
        2:_OAK_067
        5:_OAK_077
        7:_OAK_057
      end;
  end;


  Modes:

  (OTI 067/077/087)

  4Eh  T    80   60  16  (8x8)      Not all 067's
  4Fh  T   132   60  16  (8x8)
  50h  T   132   25  16  (8x14)
  51h  T   132   43  16  (8x8)
  52h  G   800  600  16  PL4
  53h  G   640  480 256  P8
  54h  G   800  600 256  P8
  55h  G  1024  768   4 ??
  56h  G  1024  768  16  PL4
  57h  G   768 1024   4  ??
  58h  G  1280 1024  16  PL4
  59h  G  1024  768 256  P8     OTI-077/87 only
  5Ah  G   640  480 64k  P16    OTI-077 w/Sierra
  5Bh  G   640  400 32k  P15    OTI-077 w/Sierra
  5Ch  G   640  480 32k  P15    OTI-077 w/Sierra
  5Dh  G   800  600 32k  P15
  5Eh  G  1280 1024 256  P8
  5Fh  G   640  480 16m  P24
  60h  G   800  600 64k  P16
  61h  G   640  400 256  P8

Note that the OAK-087 BIOS version 1.01B does not set the DAC mode of the
HiColor modes correctly.


  (OTI037C "UNIQUE" VGA)

  50h  T   132   25  16  (8x14)
  51h  T   132   43  16  (8x8)
  52h  G   800  600  16  PL4


  (OTI037C with NEL Electronics BIOS)

  50h  G   640  480  16  PL4
  51h  T    80   30      (16x9)
  52h  G  1024  480  16  PL4
  53h  T    80   25      (16x8)
  54h  T   132   43      (8x8)
  55h  T   132   25      (14x8)
  56h  T   132   43      (8x9)
  57h  T   132   25      (14x9)
  58h  T    80   43      (8x8)
  59h  T    80   43      (8x9)
  5Ah  T    80   60      (8x8)
  5Bh  G   800  600  16  PL4
  5Ch  T   100   37      (16x8)
  5Dh  T   100   75      (8x8)
  5Eh  G   800  600  16  PL4
  6Ah  G   800  600  16  PL4
  6Bh  T   100   37      (16x8)

----------10FF-----------------------------------
INT 10 - VIDEO - OAK VGA BIOS v1.02+ - SET EMULATION
        AH = FFh
        AL = Emulation
               43h  CGA emulation
               45h  EGA emulation
               4Dh  Hercules emulation
               56h  VGA emulation
        ES:DI -> signature string "Calamity"
Switches to the desired emulation