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Polygone Eine andere Welt: Sega Genesis

Übersetzung des fünften Artikels in der Reihe von Fabien Sanglard , diesmal über einen anderen Welthafen auf Sega Genesis .


Die Entwicklung von MegaDrive / Genesis begann unmittelbar nach der Einführung des Mastersystems durch Sega im Jahr 1987. Zu dieser Zeit war es Segas Ziel, etwas zu schaffen, das die PC Engine von NEC und Famicom von Nintendo übertrifft.




Artikelserie


  1. Polygone Eine andere Welt .
  2. Polygone Eine andere Welt: Amiga 500 .
  3. Polygone Eine andere Welt: Atari ST .
  4. Another World: IBM PC.
  5. Another World: Sega Genesis.



16- . , 29 1988 , , 400 000 . NES , MegaDrive .



( 1989 .) ( 1990 .) [1]. 1990 , Sega America. , , («Genesis does what Nintendon't») Altered Beast Sonic the Hedgehog Genesis -.



Nintendo SNES NEC TurboGrafx-16, Sega 1992 65% 16- Nintendo 1990 1994 . 39,7 [2].





, Genesis Motorola 68000 (7,61 ), 8 , 64 , 64 , ASIC (13 ) Z-80 (3,58 ) 8 TI 76489 YM 2612.






, , VDP (Video Display Processor). VRAM CRAM, .


, 68000 VRAM, «» VDP , RAM. DMA , RAM VRAM. VDP VRAM /, .


68000 DMA , Z-80 , .


DMA BLANK , 68000. , 68000 .


— Genesis Developer Manual

Atari ST 3 , 9 .






(VDP)


VDP ASIC . , . [3], Scroll B, Scroll A, Windows Sprites.



Scroll A Scroll B . , . Scroll A «Window», HUD .


4- (, ). 0 . 15 [4]. 128 , CRAM.


VDP , , . () , ( 0). , Z- Scroll B, , Sprite, . VDP , .




8x8. 32 , 8 .



VRAM (64 ):
==========================

WORD | WORD | WORD | WORD |
-----------------------------------------------------
BYTE | BYTE | BYTE | BYTE | BYTE | BYTE | BYTE | BYTE
-----------------------------------------------------
0 0 F F F F 0 0 0 F 0 0 0 0 F 0
F 0 F 0 F 0 0 F F 0 F 0 F 0 0 F
F 0 0 0 0 F 0 F F 0 F F F 0 0 F
0 F 0 0 0 0 F 0 0 0 F F F F 0 0

(8 8 ):
=============================

0 0 F F F F 0 0
0 F 0 0 0 0 F 0
F 0 F 0 F 0 0 F
F 0 F 0 F 0 0 F
F 0 0 0 0 F 0 F
F 0 F F F 0 0 F
0 F 0 0 0 0 F 0
0 0 F F F X 0 0

« »[5].


80 . , , 88 3232. ( 512x512, ) « »[6].


: «H32» 32x28 (256x224 ) «H40» 40x28 (320x224 ).



NTSC vs PAL


. PAL 576 , NTSC 486 . Genesis , PAL 30 ( , NTSC 28). . , .





— MegaDrive, Sonic The Hedgehog, 17% ( ). , VBLANK, , 16 . PAL 50 , NTSC 60 , VBLANK 20 , 16.



Another World Genesis


Genesis — , , Delphine Software. Interplay Genesis, Macintosh, Super Nintendo Apple IIGS.


Sega , . Genesis 68000, Atari ST .


Interplay , TV [7]. Out Of This World. , Out Of This World 1991 [8], .


Interplay , , .





, , GenS Exodus, .




Genesis[9] — , DMA. , , VDP , , Another World .


VDP DMA FILL[10] , Amiga Blitter. DMA COPY[11] VM COPY. , .


-, VRAM. 320x200 VRAM — 64 . , , , .


-, DMA FILL 16- , , , VRAM VDP, .


, , DMA FILL. Another World , (4 ) 28 . DMA FILL , , .


VDP #17[12] Exodus, , DMA COPY DMA FILL .


Another World Genesis



, VDP, VRAM, Another World 68000 , , Atari ST.


, BKGD «» . 68000 .


, DMA VRAM. VBLANK «» VRAM .


, Scroll A, Gens. Scroll A , .


Atari ST , -, COPY, movem. (5%?).






VAM VRAM , , .


pixel perfect H40 320x224 . 320200, .


320x200 320 * 300/2 = 32 000 . VDP DMA[13], , NTSC 32000/11556 = 2,7 , PAL 32000/21654 = 1,4 .



DMA, /:
===============================

On VBLANK On Active Display Total
--------------------------------------------------------------------------
60 Hz 256 x 224 6118 3584 9702
320 x 224 7524 4032 11556
50 Hz 256 x 224 14329 3584 17913
320 x 224 17622 4032 21654
256 x 240 11753 3840 15593
320 x 240 14454 4320 18774

: , PAL NTSC, VRAM. - PAL MegaDrive NTSC Genesis.


RAM VRAM, , 12-15 NTSC, .



Framerate for # missed VSYNCs:
==============================

Missed VSYNCs : 0 1 2 3 4 5 6 7
-------------------------------------------------------
NTSC Framerate : 60 30 20 15 12 10 8 7
PAL Framerate : 50 25 16 12 10 8 7 6


, VDP «H32» 3228. . , , 1,3.


28x22 , 224x176 224 * 176/2 = 19,712 .


, , RAM VRAM. NTSC 19,712 / 9702 = 2 . //, 15-12 , , , [14].


PAL 19712/17913 = 1,1 . , , 2 vsync , NTSC, 16-12fps.





, . ( ). , .




- — VDP . , . , , 15. Another World 16. .


B 0x01. 0 A B 0x01. . B A, , 0x0, 0x1 B.


, . Exodus , , 0. , , BACKGROUND COLOR (, , ) .





, , . VDP, MegaDrive, , RAM/VRAM, , , .


, - , , , , , .


, , , . NTSC , PAL «» .


? . StarFox SNES / , . , Out of This World/Another world Genesis/MegaDrive.





  1. Wikipedia: Sega Genesis, .
  2. Mega Drive.
  3. Genesis Software Manual: VDP 315-5313.
  4. , HBLANK BACKGROUND REGISTER, .
  5. VDP, .
  6. VDP,
  7. (, 1964).
  8. (, 1981).
  9. Genesis Software Manual..
  10. VDP DMA FILL.
  11. VDP DMA COPY.
  12. VDP Registers 0x17.
  13. segaretro.org, MegaDrive DMA Bandwidth.
  14. Out of This World on US Model 2 Sega Genesis through S-Video.

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