Apple Games Disassembly Project - Ultima 1 

Curious how Ultima 1 rendering works? 
Curious why the original Ultima 1 runs like crap? 
 (That's a technical term for 'slow'. =) 
Curious about learning how to optimize a 6502 map renderer? 


Since I couldn't find any *good* technical notes 
about the original Ultima 1 for the Apple ... 


... for your viewing pleasure: 


Michael's Ultima 1 Annotated Technical Notes 


Table of Contents: 
 0. Required Materials 
 1. View outdoor tiles 
 2. Map Viewer 
 3. Fast Map Drawing 
 4. Annotated original DrawMap 
 5. Monster Shapes 
 6. Bootstrapping 
 7. Applesoft Variables 
 8. Bugs 
 9. Misc. 


0. Required Materials 
= = = = = = = = = = 
 (x) Ultima 1 (Original 1981 DOS3.3 version) disks/images 
     Notes: 
       I mounted drive 1 with: ultima_1.dsk.gz 
       I mounted drive 2 with: ultima_2.dsk.gz 
     from Asimov: /games/rpg/ultima/ultima_I/ 
       After unzipping if they don't have the '.dsk' 
     extension rename them so they do. 
 (x) Apple ][ (real or emulator) 


You can tell which version you have by the border 
 No map border = original 1981 
 Blue map border = re-released 1986 remake 


1. View outdoor tiles 
= = = = = = = = = = = 


 1. Boot Ultima 1 
 2. At the ] prompt press CTRL-RESET twice 
    (AppleWin: Ctrl-F2) 
 3. Type 
    (or copy and use Shift-Insert to paste into AppleWin) 
BLOAD ULTSHAPES,A$800 
BLOAD DRAW 64.OBJ,A$A00 
CALL-151 
6:9 5 80 
1000:00 10 20 30 40 50 60 70 
1040:80 90 A0 B0 C0 D0 E0 F0 
F3E2G 
C052 
A00G 


To get back to Applesoft 
C053 
<Ctr-C> RETURN 
TEXT 


Tiles: (in hex) 
 00 Water 
 10 Land 
 20 Woods 
 30 Mountains 
 40 Castle (top-down) 
 50 Sign 
 60 Town/City 
 70 Dungeon 
 80 Fighter (and Avatar) 
 90 Horse 
 A0 Cart 
 B0 Raft 
 C0 Pirate Ship 
 D0 Hover Car 
 E0 Space Shuttle 
 F0 Time Machine 


To draw the map from Applesoft: 
 CALL 2560 


2. More Fun - Map Viewer 
= = = = = = = = = = = = 


First, load the necessary data and code... 
BLOAD ULTSHAPES,D1,A$800 
BLOAD DRAW 64.OBJ,D1,A$A00 
BLOAD BTERRA0,D2,A$1000 


Then enter this program to view the world =) 


CALL-151 
- - - - - 8< - - - - - 
C00:20 E2 F3 A9 81 85 08 85 
C08:EB D0 20 AD 8B 0A C9 0A 
C10:D0 04 A9 0C D0 06 C9 0C 
C18:D0 05 A9 0A 8D 8B 0A A5 
C20:EB 49 01 85 EB AA 9D D2 
C28:BF D0 06 A9 20 85 06 85 
C30:07 20 00 0A A5 06 20 DA 
C38:FD A9 A0 20 ED FD A5 07 
C40:20 DA FD A9 A0 20 ED FD 
C48:AE C5 0C E8 8A 20 ED FD 
C50:20 8E FD AD 00 C0 10 FB 
C58:8D 10 C0 C9 8D F0 47 C9 
C60:8B F0 43 C9 AF F0 3B C9 
C68:8A F0 37 C9 88 F0 2E C9 
C70:95 F0 26 C9 A0 F0 B2 C9 
C78:9B F0 8E C9 D1 F0 2C C9 
C80:B1 90 D0 C9 B5 B0 CC AA 
C88:CA 8E C5 0C A2 00 BD B8 
C90:0C F0 0C 20 BD 9E E8 D0 
C98:F5 E6 06 E6 06 C6 06 18 
CA0:90 8F E6 07 E6 07 C6 07 
CA8:18 90 F5 A0 03 A9 00 C6 
CB0:B8 91 B8 88 10 FB 60 EA 
CB8:84 C2 CC CF C1 C4 A0 C2 
CC0:D4 C5 D2 D2 C1 BE AC C1 
CC8:A4 B1 B0 B0 B0 8D 00 
- - - - - 8< - - - - - 
C00G 


Map Viewer Keys 
 RETURN Move Up (or Up arrow) 
 /      Move Down (or Down arrow) 
 <-     Move Left 
 ->     Move Right 
 Space  Teleport to center of map 
 1      Load map 0 (Lands of Lord British) 
 2      Load map 1 (Lands of the Feudal Lords) 
 3      Load map 2 (Lands of the Dark Unknown) 
 4      Load map 3 (Lands of Danger and Despair) 
 ESC    Toggle fullscreen 
 Q      Exit 


Note: Prints X Y W, where W is the map/world last loaded 


For map details: 
 http://shrines.rpgclassics.com/pc/ultima1/overworld.shtml 


Annoted Ultima 1 (original) MapViewer 1e 


 C00:20 E2 F3        JSR HGR 
 C03:A9 81           LDA #81     ; sprite #80 = Fighter (vehicle = 
none), #1 = MixedMode 
 C05:85 08           STA $8      ; player vehicle 
 C07:85 EB           STA $EB     ; FullScreenFlag 
 C09:D0 20           BNE .warp 
 C0B:AD 8B 0A TFS    LDA $0A8B   ; have custom DrawMap Patch 
v4? 
 C0E:C9 0A           CMP #A 
 C10:D0 04           BNE .mix 
 C12:A9 0C           LDA #C 
 C14:D0 06           BNE .doFS 
 C16:C9 0C    .mix   CMP #C 
 C18:D0 05           BNE .tfs 
 C1A:A9 0A           LDA #A 
 C1C:8D 8B 0A .doFS  STA $0A8B 
 C1F:A5 EB    .tfs   LDA $EB     ; ToggleFullScreen 
 C21:49 01           EOR #1 
 C23:85 EB    .fs    STA $EB     ; FullScreen 
 C25:AA              TAX 
 C26:9D D2 BF        STA $BFD2,X ; $BFD2+$80 = $C052 or $C053 
 C29:D0 06           BNE .draw   ; don't reset player position 
 C2B:A9 20    .warp  LDA #20     ; reset player to center of map 
 C2D:85 06           STA PlayerX 
 C2F:85 07           STA PlayerY 
 C31:20 00 0A .draw  JSR DrawMap 
 C34:A5 06           LDA $06 
 C36:20 DA FD        JSR PRBYTE  ; $FDDA 
 C39:A9 A0           LDA ' ' 
 C3B:20 ED FD        JSR COUT    ; $FDED 
 C3D:A5 07           LDA $07 
 C40:20 DA FD        JSR PRBTE   ; $FDDA 
 C43:A9 A0           LDA ' ' 
 C45:20 ED FD        JSR COUT    ; $FDED 
 C48:AE C5 0C        LDX LOAD+#D ; last loaded map, bterra# 
 C4B:E8              INX 
 C4C:8A              TXA 
 C4D:20 ED FD        JSR COUT    ; $FDED 
 C50:20 8E FD        JSR CROUT   ; $FD8E -> $FDED 
 C53:AD 00 C0 .key   LDA Key 
 C56:10 FB           BPL .key 
 C58:8D 10 C0        STA KeyStrobe 
 C5B:C9 8D           CMP kRETURN ; #$8D Return 
 C5D:F0 47           BEQ .up 
 C5F:C9 8B           CMP kUP     ; #$8B Ctrl-K ^ 
 C61:F0 43           BEQ .up     :             | 
 C63:C9 AF           CMP kSLASH  ; #$AF / 
 C65:F0 3B           BEQ .dn     ;             | 
 C67:C9 8A           CMP kDOWN   ; #$8A Ctrl-J v 
 C69:F0 37           BEQ .dn 
 C6B:C9 88           CMP kLEFT   ; #$88 Ctrl-H <-- 
 C6D:F0 2E           BEQ .lEFT 
 C6F:C9 95           CMP kRIGHT  ; #$95 Ctrl-U --> 
 C71:F0 26           BEQ .rIGHT 
 C73:C9 A0           CMP kSPACE  ; #$A0 ' ' 
 C75:F0 B2           BEQ .pos 
 C77:C9 9B           CMP kESC    ; #$9B ESC 
 C79:F0 8E           BEQ TFS     ; ToggleFullScreen 
 C7B:C9 D1           CMP 'Q'     ; #$D1 'Q' 
 C7D:F0 2C           BEQ .done 
 C7F:C9 B1           CMP '1'     ; <  '1' 
 C81:90 D0           BCC .key 
 C83:C9 B5           CMP '5'     ; >= '5' 
 C85:B0 CC           BCS .key 
 C87:AA              TAX 
 C88:CA              DEX 
 C89:8E C5 0C        STX LOAD+#D ; bterra# 
 C8C:A2 00           LDX #0 
 C8E:BD B8 0C .load  LDA $0CC0,X 
 C91:F0 0C           BEQ .2draw  ; to lazy to calculate .draw offset 
 C93:20 BD 9E        JSR $9EBD   ; DOS3.3 -> $9EBD CSW 
 C96:E8              INX 
 C97:D0 F5           BNE load 
 C99:E6 06    .right INC PlayerX 
 C9B:E6 06           INC PlayerX 
 C9D:C6 06    .left  DEC PlayerX 
 C9F:18       .2draw CLC 
 CA0:90 8F           BCC .draw 
 CA2:E6 07    .dn    INC PlayerY 
 CA4:E6 07           INC PlayerY 
 CA6:C6 07    .up    DEC PlayerY 
 CA8:18              CLC 
 CA9:90 F5           BCC .2draw+1 ; to lazy to calculate .draw offset 
 CAB:A0 03    .done  LDY #3       ; clear rest of input line (may have 
had a BLOAD) 
 CAD:A9 00           LDA #0       ; Applesoft: D7EB: LDY #2 LDA 
($B8),Y --> if line #0 then END 
 CAF:C6 B8           DEC $B8      ; Monitor: get 'CR' ($8D) from 
'C00G' 
 CB1:91 B8    .clear STA ($B8),Y  ;    w/o adjust, would get 'A' from 
BLOAD... 
 CB3:88              DEY          ; we can't store '$8D' as Applesoft 
would assume 'PLOT' token 
 CB4:10 FB           BPl .clear   ; $0CB3 
 CB6:60 
 CB7:EA              NOP          ; pad out to $CB8 
 CB8:84       LOAD   DB $84   ; Ctrl-D for DOS3.3 
 CB9:C2 CC CF C1 C4  ASC "BLOAD BTERRA>,A$1000" ; $BE '>' + 1 --> '?' 
$BF 
    A0 C2 D4 C5 D2 
    D2 C1 BE AC C1 
    A4 B1 B0 B0 B0 
CCD:8D 00           DB $8D, $8D, $00 


AppleWin Symbols 
 DB LOAD CB8:CCE 


 SYM MapView = C00 
 SYM .mix    = C16 
 SYM .doFS   = C1C 
 SYM .tfs    = C1F 
 SYM .fs     = C2D 
 SYM .warp   = C2B 
 SYM .draw   = C31 
 SYM .key    = C53 
 SYM .load   = C8E 
 SYM .right  = C99 
 SYM .left   = C9D 
 SYM .2draw  = C9F 
 SYM .down   = CA2 
 SYM .up     = CA6 
 SYM .done   = CAB 
 SYM .clear  = CB1 


3. Fast Map Drawing 
= = = = = = = = = = 


You can definitely tell Richard Garriot was 
still cutting his teeth learning 6502 assembly. 


Ultima 1 outdoor drawing is SLOW because: 


- it *always* draw an extra 2 bottom rows of the outside map 
  even though those are always covered by 
  the 4 line command history and status window! 
- it draws the 14x16 sprites in 2 column passes; 
  redundant HGR Y calculations at $A6E 
- The GetMapPtr at $A31 uses a SLOW Y*64 calculation 
- it doesn't use a HGR Y table 
- The map tiles are organized by column, not scanline 
  This means the blitter is horribly inefficient. 
  (The enhanced version of Ultima 1 uses a scanline blitter! =) 
- It always draws the map tile under the avatar and THEN 
  draws the vehicle instead of ONLY drawing the vehicle 
  for the player tile. This causes flicker when moving. 


Here is a faster and smaller version of DrawMap. 
 - About tTwice as fast as original 
 - Fixes the vehicle flicker 
 - Smaller! 
 - Annotated source is provided 
 - Only draws 10 visible tile rows 
 - Uses a mini HGR Y lookup table 


CALL-151 
- - - - - 8< - - - - - 
A00:38 A5 07 E9 05 85 D7 38 
A08:A5 06 E9 09 85 EF A2 00 
A10:86 09 A5 EF 85 D6 A0 00 
A18:BD 90 0A 85 FE BD 9C 0A 
A20:85 FF A2 00 86 FC A5 D6 
A28:C5 06 D0 0C A5 D7 C5 07 
A30:D0 04 A5 08 D0 1E A5 D6 
A38:C9 40 B0 1B A5 D7 C9 40 
A40:B0 15 6A 66 FC 6A 66 FC 
A48:09 10 85 FD A5 FC 65 D6 
A50:85 FC A1 FC 29 F0 AA A5 
A58:FE 85 FA A5 FF 85 FB BD 
A60:00 09 91 FA C8 BD 00 08 
A68:91 FA 88 E8 18 A5 FB 69 
A70:04 C9 40 90 E8 A5 FA 49 
A78:80 C5 FE D0 DC E6 D6 C8 
A80:C8 C0 28 D0 9D E6 D7 A6 
A88:09 E8 E0 0A D0 82 60 EA 
0A90:00 00 00 00 28 28 28 28 50 50 50 50 
0A9C:20 21 22 23 20 21 22 23 20 21 22 23 
- - - - - 8< - - - - - 
A00G 


If you Want to patch a copy of your "Master" disk 
 UNLOCK DRAW 64.oBJ 
 BLOAD DRAW 64.OBJ,A$A00 
Enter the above in... 
 BSAVE DRAW 64.OBJ,A$A00,L$200 
 LOCK DRAW 64.oBJ 


Notes: 
 For some reason DRAW 64.OBJ also includes 
 an Applesoft DRAW shape table at $B00. 
 Don't ask me why since the game also 
 loads them via: 
   BLOAD OUT.SHAPES,A$B00 


Annotated Optimized ...