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decle

Coleco, Parker Bros & Roklan

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This is a long one, so apologies in advance.

 

Whilst floating around Wikipedia I noticed that the List of Intellivision Games identified Roklan as the authors of the Coleco ports.  And it seems that they also did the Parker Bros games as well.  No doubt this is well known to most, but it was news to me, I hadn't even heard of Roklan Software.  It seems they were pretty big in the arcade porting business.  Ron Borta, the head of their games business, gave an interview to ANTIC back in 2016. As you might expect it's quite Atari centric, but it's worth a listen, if only for the host having a gentle dig about the quality of Inty Donkey Kong. ;)

 

Anyway, it got me thinking, could we tell that Coleco and Parker Bros games were written by the same company, just by inspecting the ROMs?

 

So I wrote a little script that disassembles two games and then looks for common runs of 10 or more instructions found in both games*.  The idea being that if the games were written using the same tools, they might show a greater number of larger matching chunks than titles that weren't.  Then I compared every combination of Coleco, Parker Bros and Activision game to see how similar they were.  The results can be seen in this diagram which shows the total number of shared instructions for each combination:

 

coleco.thumb.jpg.e443b355aa5ecf18e5a2be562bc45673.jpg

 

The number of matching chunks is depicted by the colour of the cell.  White means no significant shared code, then as the total size of matching chunks increases the colour changes from red to green.  I only report games with two or more common chunks, or where the average length of the chunks is more than 20 instructions.  The games are arranged by publisher and then by release date (as reported by Wikipedia).

 

What we can see from this is that there are indications that the Coleco and Parker Bros games were written by the same company.  Early Coleco games (Donkey Kong, Carnival, Mousetrap and Donkey Kong Jnr) mutually share code, and they also have some similarities with most Parker Bros games.  We can also see that, as expected, these games don't share much in common with Activision games.  It seems the later 1983 Coleco games don't have much in common with either their earlier syblings, with each other, or with the Parker Bros games which were also released in 1983.  Perhaps Zaxxon represents a transition between the two sets.  Could this represent a change in the Roklan tools or the way they developed games?

 

So the short answer to my question is yes, there are some indications baked into the ROMs that the Coleco and Parker Bros games were written using the same tools.

 

Now, you might be wondering what happens if we apply this process to the full 125 game catalogue?  Well, this is what what we see (you might want to download and pan around the image)...

 

all.thumb.jpg.fa1f6f619c40aaddd60657919b904e43.jpg

 

It looks as though "Kings of Consistency" were Imagic (blue ellipse) and Atarisoft (black ellipse).  Within the Imagic titles we can see what might be an interesting change, with the earlier games up to Microsurgeon having less in common than those that follow, and clearly Nova Blast and Truckin' seem to be oddballs.  Again perhaps this represents a switch in development tools?

 

imagic.thumb.jpg.f17c97558f9afe35bab18187f429c94d.jpg

 

It seems that overall there is much less consistency in INTV games...

 

intv.thumb.jpg.4184da2a530c72e68163d375fd8c9f27.jpg

 

...and even less for Mattel titles...

 

mattel.thumb.jpg.cc3dbd8569ba4231c38626ac6925dd7b.jpg

 

...as exemplified by the lower amount of colour.  This could be down to the fact that in many cases much of their common library code is found in the EXEC, rather than the cartridges themselves.  That said, going back to the full diagram, links between games that are known to be related can be seen, for example Math Fun and Learning Fun 1, Backgammon and Triple Challenge or Hockey and Slap Shot.  We can also see other, less obvious connections; like Tron Deadly Discs and Dig Dug, which are related through the hidden game Deadly Dogs, or Checkers and Sub Hunt which are linked through their common use of the tune Ride of the Valkyries.  Some common ancestry of games is also visible, for example Dig Dug's origins as an Atarisoft title, and Space Hawk being a derivative of the hidden game Meteor! within Astrosmash!

 

I don't think there are any unknown gems hidden amongst the shared code, but clearly there are some less obvious links, for example Auto Racing shares quite a bit in common with a number of titles including Astrosmash, Space Hawk, AD&D, Motocross, Space Spartans and Tron Solar Sailor.

 

If you fancy a dive through the data for yourself, here's the spreadsheet...

 

intyGameCommonality.ods

 


Cheers

 

decle

 

 

* The actual process is rather more involved.  For the curious...

 

Spoiler

 

The script also removes all labels and constants so it just compares chunks of mnemonics and registers like this:

 

PSHR    R5                     
CLRR    R1                     
MVII    # R4             
JSR     R5              
JSR     R5              
ADDI    # R4             
CMPI    # R4             
BLT                      
MVO     R1              
PULR    R7           

 

This means it won't get fooled by the same code being located at different memory addresses. The script also tries to account for the different ROM sizes by scaling the number of matches based on the size of smaller ROM in the comparison, reporting the number of common commands per 10,000 instructions in addition to a straight forward total.

 


 

 

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On 5/4/2021 at 8:13 AM, decle said:

This is a long one, so apologies in advance.

 

Whilst floating around Wikipedia I noticed that the List of Intellivision Games identified Roklan as the authors of the Coleco ports.  And it seems that they also did the Parker Bros games as well.  No doubt this is well known to most, but it was news to me, I hadn't even heard of Roklan Software.  It seems they were pretty big in the arcade porting business.  Ron Borta, the head of their games business, gave an interview to ANTIC back in 2016. As you might expect it's quite Atari centric, but it's worth a listen, if only for the host having a gentle dig about the quality of Inty Donkey Kong. ;)

 

Thanks for the awesome spreadsheet!  Also, the connection of Coleco to Parker Bros via Roklan Software was news to me as well.

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Thanks Decle!

This is a great in-depth analysis.

It gives a lot of insight on how our favourites were made.

I didn't know of Roklan either.

Great work.

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This is great. I think your Roklan findings are seem pretty consistent with ours.

Edited by CRV
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On 5/10/2021 at 10:52 PM, CRV said:

This is great. I think your Roklan findings are seem pretty consistent with ours.

Apologies @CRV, although I found the GDRI page on Roklan, I didn't notice your discussion with Dimitri on the discussion page, otherwise I would have referenced it and credited you.  Nice work :thumbsup:

 

On 5/4/2021 at 4:13 PM, decle said:

I don't think there are any unknown gems hidden amongst the shared code, but clearly there are some less obvious links, for example Auto Racing shares quite a bit in common with a number of titles including Astrosmash, Space Hawk, AD&D, Motocross, Space Spartans and Tron Solar Sailor

For those that were curious about the possible link between Auto Racing, Astrosmash!, Space Hawk, AD&D, Motocross, Space Spartans and Tron Solar Sailor.  It took a little thought, but once you see it, it's kind of obvious...

 

Spoiler

These games all have both horizontal and vertical scrolling of the playfield.  In the case of Astrosmash! it's hidden in the Meteor! variant, but it's there...

 

meteor.gif.4f013eb12f782961d208c2ac5794ce16.gif

 

I think these games are the only Mattel titles to use two axis scrolling, and a big chunk of the code shared between these titles is there to implement it.   Here is the smaller of two chunks of code that do just that from Meteor!  This code can also be found in Auto Racing:

        MVII    #$0100, R5           
        [email protected]    R5,     R0           
        [email protected]    R0,     R4           
        [email protected]    R5,     R0           
        [email protected]    R0,     R4           
        MVII    #$00A1, R0           
        MVII    #$005E, R1           
        MVO     R0,     .ISRVEC.0    
        MVO     R1,     .ISRVEC.1    
L_5E82:
        EIS                          
        MVI     G_019C, R2           
        SARC    R2,     2            
        BNC     L_5E9B               
        BOV     L_5E82               

        JSR     R5,     L_5738       

        MVII    #$0003, R2           
        MVO     R2,     G_019C       
        MVII    #$00D5, R0           
        MVII    #$005E, R1           
        MVO     R0,     .ISRVEC.0         
        MVO     R1,     .ISRVEC.1         
        B       L_5E82                    
L_5E9B:
        BNOV    L_5EA0                    

        JSR     R5,     L_5738            

L_5EA0:
        PULR    R7                        
        PSHR    R5                        
        MVI     G_0190, R4                
        TSTR    R4                        
        BEQ     L_5EAC                    

        MVI     G_0193, R4                
        TSTR    R4                        
L_5EAA:
        BNEQ    L_5ECA                    

L_5EAC:
        JSR     R5,     L_5F98            

        MVI     G_0189, R0                
        MVO     R0,     .STIC.HDLY        
        MVI     G_018C, R0                
        MVO     R0,     .STIC.VDLY        

        JSR     R5,     L_5EFB            

        CLRR    R2                        
        SUBI    #$0008, R2                

        JSR     R5,     L_5F07            
        JSR     R5,     L_5F3A            

        TSTR    R2                        
        BMI     L_5EDF                    

 

 

This is exactly the kind of finger-printing of the ROMs I was hoping to find.

 

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Looking at the Mattel games, I wonder if there are any conclusions to be drawn by separating the games developed by APh Technological Consulting, which also developed the Exec operating system, and the games developed internally by the Blue Sky Rangers.

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