Metal Gear annotated disassembly published

By Dustin Pease

Resident (50)

06-10-2018, 00:05

Manuel,
You are awesome. Thank you so much for this!

By Victor

Champion (480)

06-10-2018, 05:27

What a titanic work...

Thanks for sharing, Manuel!!

By Pippo

Champion (454)

06-10-2018, 07:31

Astonishing work!!!
You spent very happy hours, didn't you, Master Manuel?

By cax

Prophet (3735)

06-10-2018, 07:56

Very impressive. Can you share the insights now - e.g. how many different code styles can you spot, hidden features etc. ?

By Pippo

Champion (454)

06-10-2018, 08:07

Many, many thanks, Master Manuel, for your deep dedication to the Sacred System.

By Guillian

Prophet (3328)

06-10-2018, 09:00

Thanks guys!

@cax: there are at least two different coding styles. In this Twitter thread I posted some oddities (most of them in Spanish). There are a few more commented in the code.

By KdL

Paragon (1305)

06-10-2018, 11:35

Congrats Manuel !!

By Pencioner

Scribe (1140)

06-10-2018, 12:09

Great stuff! Can't imagine how much of efforts has been put on this

By ren

Paragon (1459)

06-10-2018, 13:38

Wow.. So I guess we might expect some fan game(s) / 'remixes' based on these sources..?

Would there be other works you're interested in to disassemble? Gradius 2 or Usas perhaps?

By Guillian

Prophet (3328)

06-10-2018, 15:14

Thanks!

@ren: I could do the same with other games, but... not really sure if it is worth the effort.

By sd_snatcher

Prophet (3296)

06-10-2018, 15:49

Impressive, Snake! I mean, Manuel!

By Wolverine_nl

Paragon (1102)

06-10-2018, 16:05

Great job Manuel!
It is nice to see in the 80's Konami kitchen this way. Your effort was definitly worth it.

By gdx

Prophet (3571)

06-10-2018, 16:11

Thanks for sharing this impressive work.
Which disassembler did you use?

By lintweaker

Champion (267)

06-10-2018, 16:12

Wow, great job!

By Giangiacomo Zaffini 2

Master (212)

06-10-2018, 19:53

Thank Manuel for his gigantic effort.
I cannot even imagine how to revert machine code blob into source assembly modules, functions and variables.
Are You an university resercher or university instructor or professor?

By Guillian

Prophet (3328)

06-10-2018, 21:59

Thanks!

@gdx: I used IDA

@Giangiacomo: I'm not related to univertity or teaching. I'm just a MSX fan (^_^)

By Meits

Scribe (5899)

06-10-2018, 22:54

But... Are there things you can NOT do as well?

By konamiman

Paragon (1077)

07-10-2018, 12:15

Meits wrote:

But... Are there things you can NOT do as well?

He almost can't write README files.

By Guillian

Prophet (3328)

07-10-2018, 13:02

konamiman wrote:

Meits wrote:

But... Are there things you can NOT do as well?

He almost can't write README files.

Hahahaha!
That's true!

By Huey

Prophet (2651)

08-10-2018, 14:09

Great work!

I've spend already quite some time reading the code and going through the structures.

By Guillian

Prophet (3328)

08-10-2018, 15:51

Thanks, Huey!
I hope you will find it interesting.

By Giangiacomo Zaffini 2

Master (212)

08-10-2018, 16:49

I tested it, if I'm not mistaken, sjasm 0.39c compiles codebase but sjasm 0.42c does not compile.

It is quite a feeling having such Metal Gear compiled in a second after enter key smashed.

By iamweasel2

Hero (577)

09-10-2018, 05:41

This is amazing ! Thanks very much for this great work !

If I may suggest, it would be nice a full dissassembly of a small classic MSX game (16 k). Anyone would do: Hyper Rally, King's valley, Hero, River Raid etc... It would help a lot for people learning asm if they could understand how to code a small msx action game.

By theNestruo

Master (159)

09-10-2018, 06:47

Thank you, Manuel!!!
I love reading code to discover different approaches and alternative solutions, and usually to improve my own code.
It's great to study how Konami did some things (such as reading input; much easier than what I was trying to do!).

iamweasel2 wrote:

If I may suggest, it would be nice a full dissassembly of a small classic MSX game (16 k). Anyone would do: Hyper Rally, King's valley, Hero, River Raid etc... It would help a lot for people learning asm if they could understand how to code a small msx action game.

Does Pyramid Warp (T&E, 1983) qualify? https://github.com/theNestruo/msx-pyramidwarpex

By Guillian

Prophet (3328)

09-10-2018, 09:55

@Giangiacomo The sources compile with sjasm 0.39 as explained in the readme. But it is possible to adapt them to work with 0.42 (Fernando García aka Bitvision did it)

@iamweasel2 Perhaps in a future I'll release more sources/disassemblies (King's Valley, Knight Lore, etc.)

@theNestruo It is nice to hear that the sources are helping to improve your game!

By Manuel

Ascended (16702)

09-10-2018, 21:20

Guillian: just wondering: of that 128kB, how much is code, how much is data? And how is the data divided? I guess mostly graphics and map data. Any idea of how much of each?

By Sandy Brand

Master (186)

10-10-2018, 00:11

Wow! That is some really impressive retro archeology!

By Guillian

Prophet (3328)

10-10-2018, 09:00

Manuel: a rough estimation could be about 36 kB of code, 16 kB of sprites, 8 kB of music/sfx, 6 kB of text, 32 kB of graphics, 10 kB of rooms, 10 kB of metaTiles, 10 kB other data.

By Manuel

Ascended (16702)

10-10-2018, 22:21

Thanks Interesting!

By Edevaldo

Master (135)

12-10-2018, 05:14

Quote:

Manuel: a rough estimation could be about 36 kB of code, 16 kB of sprites, 8 kB of music/sfx, 6 kB of text, 32 kB of graphics, 10 kB of rooms, 10 kB of metaTiles, 10 kB other data.

I was very curious about that as well. Thanks!

Could you comment on your disassemble process? I would like to try it on a simpler game.

By theNestruo

Master (159)

12-10-2018, 11:41

I'm used to use zero flag (z) for true/false return values, and I can see that carry flag (c) is widely used here.
Is it usual in Z80 assembler to use C for that purpose? Is my BASIC and C background tricking me to think in terms of Z/NZ?

By Guillian

Prophet (3328)

12-10-2018, 14:34

Edevaldo wrote:

Could you comment on your disassemble process? I would like to try it on a simpler game.

Probably it is easier to show it on a video that explain it. It can be done in different ways:

- 1st pass: disassembly, analyze and annotate the flow of the program
- 2nd pass: fix the parts that were wrongly identified

Or:
- 1st pass: Fully disassembly the code
- 2nd pass: Analyze and annotate the code
- 3rd pass: Fixes

theNestruo wrote:

I'm used to use zero flag (z) for true/false return values, and I can see that carry flag (c) is widely used here.
Is it usual in Z80 assembler to use C for that purpose? Is my BASIC and C background tricking me to think in terms of Z/NZ?

It depends on what you need to check. I.e.: checking threshold values, or if a value in within a range, the C and NC are better choices.

By ren

Paragon (1459)

12-10-2018, 16:39

Guillian wrote:

I could do the same with other games, but... not really sure if it is worth the effort.

May I ask you how long you've been working on this disassemble?

Some n00b questions from me.. I now very little (to nothing) about assembly language, but I reckon having it disassembled says (to an extend) nothing about any higher level language the programmers might have used, right? Or are there any conclusion you can draw based on what you've seen/come across?

I wonder to what extend the structure you present the disassemble in, also represents the source structure Konami employed? High probability, or some guesses/own interpretations here & there?

Cheers / thanks for illuminating!

By iamweasel2

Hero (577)

12-10-2018, 16:57

theNestruo wrote:

Thank you, Manuel!!!
I love reading code to discover different approaches and alternative solutions, and usually to improve my own code.
It's great to study how Konami did some things (such as reading input; much easier than what I was trying to do!).

iamweasel2 wrote:

If I may suggest, it would be nice a full dissassembly of a small classic MSX game (16 k). Anyone would do: Hyper Rally, King's valley, Hero, River Raid etc... It would help a lot for people learning asm if they could understand how to code a small msx action game.

Does Pyramid Warp (T&E, 1983) qualify? https://github.com/theNestruo/msx-pyramidwarpex

Of course it qualifies ! :) Thanks very much theNestruo, I'll check it out. :)

By Guillian

Prophet (3328)

12-10-2018, 20:44

ren wrote:

May I ask you how long you've been working on this disassemble?

I disassembled the game and analyzed it in two months one year ago.
Then two months ago I started adding annotations.
So it took me about 4 months in my spare time.

ren wrote:

Some n00b questions from me.. I now very little (to nothing) about assembly language, but I reckon having it disassembled says (to an extend) nothing about any higher level language the programmers might have used, right? Or are there any conclusion you can draw based on what you've seen/come across?

I'm almost 100% sure that the game was programmed in assembler.

ren wrote:

I wonder to what extend the structure you present the disassemble in, also represents the source structure Konami employed? High probability, or some guesses/own interpretations here & there?

I have no idea how Konami structured the code. But I know they reused different "modules", that probably they included/imported into different projects (i.e.: the code for the Konami logo, for reading and storing the controls, for calculating the trajectory/speed of a shot, etc.)

The main structure in all Konami games is almost the same, except in some of them that were not really made by Konami (i.e: Contra, or Green Beret)

By MOA

Champion (293)

16-10-2018, 00:56

Wow, very well done!

This was definitely written in assembly by the Konami coders; no compiler would generate such code. Code quality is actually very decent; much better than I would expect from a company trying to make money, hehe.

By Wolverine_nl

Paragon (1102)

16-10-2018, 09:22

MOA wrote:

Wow, very well done!

This was definitely written in assembly by the Konami coders; no compiler would generate such code. Code quality is actually very decent; much better than I would expect from a company trying to make money, hehe.

Unlike some nowadays, that release a game which isn't a 100% finished game yet. And you get an update every other day.
The old days, games needed to be 100% working.

By Grauw

Ascended (9181)

16-10-2018, 09:42

theNestruo wrote:

I'm used to use zero flag (z) for true/false return values, and I can see that carry flag (c) is widely used here.
Is it usual in Z80 assembler to use C for that purpose? Is my BASIC and C background tricking me to think in terms of Z/NZ?

I use both as is convenient, but I prefer carry as it's easier to set explicitly (scf/ccf/and a), is modified by less instructions (e.g. inc & bit don't), and is easier to use directly in math (e.g. sbc a,a); with the zero flag you always need to branch.

By theNestruo

Master (159)

20-10-2018, 16:29

Grauw wrote:

theNestruo wrote:

I'm used to use zero flag (z) for true/false return values, and I can see that carry flag (c) is widely used here.
Is it usual in Z80 assembler to use C for that purpose? Is my BASIC and C background tricking me to think in terms of Z/NZ?

I use both as is convenient, but I prefer carry as it's easier to set explicitly (scf/ccf/and a), is modified by less instructions (e.g. inc & bit don't), and is easier to use directly in math (e.g. sbc a,a); with the zero flag you always need to branch.

Thanks, Grauw! That makes a lot of sense!
I'll check my code because I'll probably can improve some parts switching from z to c

By nikodr

Paladin (744)

22-10-2018, 00:36

Could a level editor for metal gear be released that would allow us to make new maps or scenarios?now that this difficult -(manuel you are truly a genius)- rom has been dissasembled could that happen?
Also what other tricks could programmers get out of those routines?do you think that those tricks they used back then are suitable for making games on the msx now?

By Guillian

Prophet (3328)

22-10-2018, 09:19

It is possible to modify the map, rooms, items locations, etc. It is, somehow, easy to do it. Probably the difficult part is the design.

About the tricks. Some parts are not optimized, but the sources are a good source of information for learning. E.g.: how to read controls, sprite flickering routine, state machines, actors structures, etc.

By FiXato

Scribe (1602)

23-10-2018, 05:58

Modifying item locations is already possible with Randomizer for Metal Gear 1 objects.

By nikodr

Paladin (744)

26-10-2018, 10:48

I am still amazed by the fact that konami has no main loop actually but everything is done with the dummy loop calling the isr.also the camera logic and testing if enemies can see you while was good in 1987 now in metal gear 2 they changed it.could it change here?so enemies can see you if you in front of them?many times if you go up a wall and enemy is in front of you he doesnt see you.

Metal Gear annotated disassembly published

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