CBM64 Bard's Tale 1 Disassembly
Re: CBM64 Bard's Tale 1 Disassembly
What does "BAD" mean in the disassembled code?
Re: CBM64 Bard's Tale 1 Disassembly
Same as ??? I guess, meaning that the binary value is not a valid machine code instruction, like when you disassemble data?Jojo80011 wrote:What does "BAD" mean in the disassembled code?
Or there may be some undocumented instructions that are not supported by the disassembler? I'm guessing as I don't know for certain, but BAD certainly is not listed in the 6502 instruction set.
Re: CBM64 Bard's Tale 1 Disassembly
Flaminal is right: BAD means an illegal opcode or an opcode that really has no (known) function. But BT is completely coded with legal codes, so likely you disassembled beyond the boundaries of regular code into a data section.
Re: CBM64 Bard's Tale 1 Disassembly
I compared all weapons in your bt1 json files with the html-tables on wikia.
http://bardstale.wikia.com/wiki/Tales_o ... wn_:_Items
most items there are perfectly correct. only a few things to debate:
thief dagger on wikia states that he increases chance to hide, but there is nothing inside the json-file to confirm this. can you confirm it, zerozero?
wikia says Arcs Hammer casts a LERE if you use it. your json file says the light of arcs hammer is stronger: according to the json file, arc hammers distance is 5, while LERE has a distance of 4 (see spell.json).
conjurstaff is known to halve spell costs even if it is not equiped. this feature is missing in the json-file. can you confirm it?
are there any other items that work without the need to equip them? would be nice
http://bardstale.wikia.com/wiki/Tales_o ... wn_:_Items
most items there are perfectly correct. only a few things to debate:
thief dagger on wikia states that he increases chance to hide, but there is nothing inside the json-file to confirm this. can you confirm it, zerozero?
wikia says Arcs Hammer casts a LERE if you use it. your json file says the light of arcs hammer is stronger: according to the json file, arc hammers distance is 5, while LERE has a distance of 4 (see spell.json).
conjurstaff is known to halve spell costs even if it is not equiped. this feature is missing in the json-file. can you confirm it?
are there any other items that work without the need to equip them? would be nice
Re: CBM64 Bard's Tale 1 Disassembly
can someone answer the following question after disassembling the code?
resistence and classes:
do all classes have the same resistance (chance to avoid spell damage) if they have the same luck-value, level and the same items equipped? is there a class-bonus to resistance or do some classes get more resistence per level-up?
as far as i know, luck and level affect the chance to resist a spell, is that correct?
resistence and classes:
do all classes have the same resistance (chance to avoid spell damage) if they have the same luck-value, level and the same items equipped? is there a class-bonus to resistance or do some classes get more resistence per level-up?
as far as i know, luck and level affect the chance to resist a spell, is that correct?
Re: CBM64 Bard's Tale 1 Disassembly
Paladins get a resistance bonus based on level from +1 to +6. The other classes get a static bonus between +1 and +3.Mordred wrote:can someone answer the following question after disassembling the code?
resistence and classes:
do all classes have the same resistance (chance to avoid spell damage) if they have the same luck-value, level and the same items equipped? is there a class-bonus to resistance or do some classes get more resistence per level-up?
as far as i know, luck and level affect the chance to resist a spell, is that correct?
Level and Luck do affect the spell resistance.
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Re: CBM64 Bard's Tale 1 Disassembly
Hey! Mad props to Darendor and ZeroZero for keeping this thing going for almost five years now.
A parenthetical note is that if you see a lot of nonsense instructions you're seeing data, not a program. (or, as I found in my partial disassembly of BT1 on the Apple, obfuscated code)
A parenthetical note is that if you see a lot of nonsense instructions you're seeing data, not a program. (or, as I found in my partial disassembly of BT1 on the Apple, obfuscated code)
Re: CBM64 Bard's Tale 1 Disassembly
I only wished, that Burgerbecky could decide to publish the complete sources of BT1. She was so kind to send me some snippets to get me on the track.
Imho BT had the most sophisticated RPG-Engine on the CBM64 ever, but thats only my 2 cents.
Imho BT had the most sophisticated RPG-Engine on the CBM64 ever, but thats only my 2 cents.
Re: CBM64 Bard's Tale 1 Disassembly
Agreed. I was always in awe of how sophisticated the graphics compression of BT1 must be. I had BT1 on tape, and and each dungeon level would be a short load - which unbelievably included monster graphics!ZeroZero wrote:Imho BT had the most sophisticated RPG-Engine on the CBM64 ever, but thats only my 2 cents.
I had similar thoughts when I saw the BT1 disk intro animations for the first time.
Re: CBM64 Bard's Tale 1 Disassembly
In one of the articles here the animation mechanism is explained (based on the excellent work of tedious). Afaik the title animation is done the very same way. I made a little proggy in VB6 in 2010 that loads anims directly from a D64-Image and displays them. Although the title bar reads "Editor" it rather is a viewer - no encoding or editing is implemented.Flanimal wrote: Agreed. I was always in awe of how sophisticated the graphics compression of BT1 must be.
...
I had similar thoughts when I saw the BT1 disk intro animations for the first time.
Re: CBM64 Bard's Tale 1 Disassembly
No posts here the last 3 years, so I want to open again this topic.
It's because I woundering why the 'character change to hit' sould be a comparison of the armor classes.
I already disassembled, or better investigated, this part of the code in the 80s. But since my notices were lost over the years, I did it again. And it was a lot of fun .
Unfortunately the 'character-chance-to-hit' code is very long with many subs. Therefore I will just mention the addresses. But the code can be found on your C64 .
start: $58D1
1. load AC of monster from table $7DA8 (only the 5 right bits) in ZP (zero page) $4A
(example: AC 7 => 03h =>$4A; AC L0 => 14h => $4A)
2. check if weapon with a bonus is equiped (jsr $5A6E); the weapon bonus can be found in table $A377 (MSB); if yes, e.g. mthr sword (+1), subtract the weapon bonus from $4A and store the result in $4A
(example: AC 7 => 02h; AC L0 => 13h)
3. substract class bonus (located in table $82B5 + class index) from $4A and store the result in $4A
(example: warrior with class bonus 2; AC 7 => 00h; AC L0 => 11h)
4. substract party bonus, which is stored in ZP $40, from $4A and store the result in $4A
(example: bard song 2 => group bonus +1; AC 7 => 00h; AC L0 => 0Ah)
5. add party malus (stored in ZP $DF) to $4A and store the resut in $4A
(example: not tested yet; maybe if party is affected by the spells FRFO, FEAR or CURS)
6. check if AC of monster ($4A) > 15h; if yes, set it to 15h; if not => next step
7. store this value in ZP $3B
(example: AC 7 => 00h; AC L0 => 0Ah)
8. create a random number by using jsr $18CE twice and add 03h to this random number; result is between 3 and 17 (decimal).
(example: 09h)
9. add character bonus (stored in table $82FA + character no) to the random number
(example: character is affected by BASK, which adds 04h; 09h + 04h => 0Dh)
10. compare this value (0Dh) with the AC of the monster; in our example, both, AC 7 (00h) and AC L0 (0Ah) are lower than 0Dh => hit; without BASK => 09h => only AC 7 is a hit and AC L0 is missed.
Just a short summary:
hit: if monster AC - item bonus - class bonus - group bonus + group malus < random no (3-17 dec) + character bonus
It's very interesting that there is no level bonus for the 'chance to hit'.
It's because I woundering why the 'character change to hit' sould be a comparison of the armor classes.
I already disassembled, or better investigated, this part of the code in the 80s. But since my notices were lost over the years, I did it again. And it was a lot of fun .
Unfortunately the 'character-chance-to-hit' code is very long with many subs. Therefore I will just mention the addresses. But the code can be found on your C64 .
start: $58D1
1. load AC of monster from table $7DA8 (only the 5 right bits) in ZP (zero page) $4A
(example: AC 7 => 03h =>$4A; AC L0 => 14h => $4A)
2. check if weapon with a bonus is equiped (jsr $5A6E); the weapon bonus can be found in table $A377 (MSB); if yes, e.g. mthr sword (+1), subtract the weapon bonus from $4A and store the result in $4A
(example: AC 7 => 02h; AC L0 => 13h)
3. substract class bonus (located in table $82B5 + class index) from $4A and store the result in $4A
(example: warrior with class bonus 2; AC 7 => 00h; AC L0 => 11h)
4. substract party bonus, which is stored in ZP $40, from $4A and store the result in $4A
(example: bard song 2 => group bonus +1; AC 7 => 00h; AC L0 => 0Ah)
5. add party malus (stored in ZP $DF) to $4A and store the resut in $4A
(example: not tested yet; maybe if party is affected by the spells FRFO, FEAR or CURS)
6. check if AC of monster ($4A) > 15h; if yes, set it to 15h; if not => next step
7. store this value in ZP $3B
(example: AC 7 => 00h; AC L0 => 0Ah)
8. create a random number by using jsr $18CE twice and add 03h to this random number; result is between 3 and 17 (decimal).
(example: 09h)
9. add character bonus (stored in table $82FA + character no) to the random number
(example: character is affected by BASK, which adds 04h; 09h + 04h => 0Dh)
10. compare this value (0Dh) with the AC of the monster; in our example, both, AC 7 (00h) and AC L0 (0Ah) are lower than 0Dh => hit; without BASK => 09h => only AC 7 is a hit and AC L0 is missed.
Just a short summary:
hit: if monster AC - item bonus - class bonus - group bonus + group malus < random no (3-17 dec) + character bonus
It's very interesting that there is no level bonus for the 'chance to hit'.
Re: CBM64 Bard's Tale 1 Disassembly
And here is the code of the monster 'chance to hit' from the C64 (Bard's Tale I):
And for Bard's Tale II (very similar):
Code: Select all
.C:5a92 A9 00 LDA #$00 ;not needed for hit detection
.C:5a94 85 C8 STA $C8 ;not needed for hit detection
.C:5a96 A5 44 LDA $44 ;load no. of character which is attacked in A
.C:5a98 0A ASL A ;double it due to 2 byte address
.C:5a99 AA TAX ;transfer A to X
.C:5a9a BD 8D 09 LDA $098D,X ;identify address of attacked character (LSB)
.C:5a9d 8D A9 5A STA $5AA9 ;and store it
.C:5aa0 BD 8E 09 LDA $098E,X ;identify address of attacked character (MSB)
.C:5aa3 8D AA 5A STA $5AAA ;and store it
.C:5aa6 A0 3F LDY #$3F ;load byte position of AC
.C:5aa8 B9 80 CB LDA $CB80,Y ;load AC of character in A
.C:5aab A6 47 LDX $47 ;load monster group no. (0-3)
.C:5aad 18 CLC
.C:5aae 7D 24 83 ADC $8324,X ;add monster group malus to A (e.g. the spell FEAR increase this value by 1)
.C:5ab1 C9 15 CMP #$15 ;compare AC with 15h
.C:5ab3 90 02 BCC $5AB7 ;if AC < 15h => jump
.C:5ab5 A9 15 LDA #$15 ;set AC to 15h (max)
.C:5ab7 8D E2 5A STA $5AE2 ;and store it
.C:5aba BC B0 03 LDY $03B0,X ;load monster type
.C:5abd B9 28 7E LDA $7E28,Y ;load attack value of monster type
.C:5ac0 29 1F AND #$1F ;use only the 5 bits from the right
.C:5ac2 4A LSR A ;half this value by moving the bits one position to the right
.C:5ac3 85 0B STA $0B ;store value
.C:5ac5 20 CE 18 JSR $18CE ;create two random numbers between 00-FF and store them in $5A and $5B
.C:5ac8 A5 5A LDA $5A ;load first random number in A
.C:5aca 29 07 AND #$07 ;use only the 4 bits from the right (value: 0-7)
.C:5acc 18 CLC
.C:5acd 65 0B ADC $0B ;add modified (in $5AC2) monster attack value to A
.C:5acf 85 0B STA $0B ;store result in $0B
.C:5ad1 A5 5B LDA $5B ;load 2nd random number in A
.C:5ad3 29 07 AND #$07 ;use only the 4 bits from the right (value: 0-7)
.C:5ad5 18 CLC
.C:5ad6 65 0B ADC $0B ;add content of $0B to the result
.C:5ad8 A6 47 LDX $47 ;load monster group no. (0-3)
.C:5ada 18 CLC
.C:5adb 7D 34 83 ADC $8334,X ;add monster group bonus to A (unclear; maybe if party is affected by FEAR or other spells)
.C:5ade 18 CLC
.C:5adf 69 02 ADC #$02 ;add 2 to A; now the final attack value of the monster is in A
.C:5ae1 C9 15 CMP #$15 ;compare monster attack value with AC of character
.C:5ae3 B0 02 BCS $5AE7 ;if monster attack value >= AC of character => HIT => jump
.C:5ae5 38 SEC
.C:5ae6 60 RTS ;if no HIT => return
Code: Select all
.C:a35f A9 00 LDA #$00 ;not needed for hit detection
.C:a361 85 C8 STA $C8 ;not needed for hit detection
.C:a363 A5 44 LDA $44 ;load no. of character which is attacked in A
.C:a365 0A ASL A ;double it due to 2 byte address
.C:a366 AA TAX ;transfer A to X
.C:a367 BD 8D AA LDA $AA8D,X ;identify address of attacked character (LSB)
.C:a36a 8D 76 A3 STA $A376 ;and store it
.C:a36d BD 8E AA LDA $AA8E,X ;identify address of attacked character (MSB)
.C:a370 8D 77 A3 STA $A377 ;and store it
.C:a373 A0 3F LDY #$3F ;load byte position of AC
.C:a375 B9 00 B8 LDA $B800,Y ;load AC of character in A
.C:a378 A6 47 LDX $47 ;load monster group no. (0-3)
.C:a37a 18 CLC
.C:a37b 7D 95 02 ADC $0295,X ;add monster group malus to A (e.g. the spell FEAR increase this value by 1)
.C:a37e C9 1F CMP #$1F ;compare AC with 1Fh
.C:a380 90 02 BCC $A384 ;if AC < 1Fh => jump
.C:a382 A9 1F LDA #$1F ;set AC to 1Fh (max)
.C:a384 8D AB A3 STA $A3AB ;and store it
.C:a387 20 02 09 JSR $0902 ;set up address for monster type => $67 (LSB) $68 (MSB)
.C:a38a A0 1D LDY #$1D ;load byte position of monster type attack value
.C:a38c B1 67 LDA ($67),Y ;load monster type attack value
.C:a38e 4A LSR A ;half this value by moving the bits one position to the right
.C:a38f 85 97 STA $97 ;store value
.C:a391 20 90 08 JSR $0890 ;create two random numbers between 00-FF and store them in $5A and $5B
.C:a394 A5 5A LDA $5A ;load first random number in A
.C:a396 29 07 AND #$07 ;use only the 4 bits from the right (value: 0-7)
.C:a398 18 CLC
.C:a399 65 97 ADC $97 ;add modified (in $A38E) monster attack value to A
.C:a39b 85 97 STA $97 ;store result in $97
.C:a39d A5 5B LDA $5B ;load 2nd random number in A
.C:a39f 29 07 AND #$07 ;use only the 4 bits from the right (value: 0-7)
.C:a3a1 18 CLC
.C:a3a2 65 97 ADC $97 ;add content of $97 to the result
.C:a3a4 A6 47 LDX $47 ;load monster group no. (0-3)
.C:a3a6 18 CLC
.C:a3a7 7D A5 02 ADC $02A5,X ;add monster group bonus to A (unclear; maybe if party is affected by FEAR or other spells)
.C:a3aa C9 07 CMP #$07 ;compare monster attack value with AC of character
.C:a3ac B0 02 BCS $A3B0 ;if monster attack value >= AC of character => HIT => jump
.C:a3ae 38 SEC
.C:a3af 60 RTS ;if no HIT => return
Re: CBM64 Bard's Tale 1 Disassembly
Only the parts I'm interested in => the melee attacks (including monster- and item tables).
I was always a bit frustrated with the high (or low) monster ACs. But now I know how to hit them
I was always a bit frustrated with the high (or low) monster ACs. But now I know how to hit them