decle Posted May 4, 2021 Share Posted May 4, 2021 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: 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)... 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? It seems that overall there is much less consistency in INTV games... ...and even less for Mattel titles... ...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. 12 6 Quote Link to comment Share on other sites More sharing options...
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