Chris White - Emulation & Decompilation

Tuesday, November 10, 2009

Extend Time!

One of the aspects of OutRun that somewhat puzzled me as a player, was exactly how the "Extend Time!" feature at the end of each level worked.

This is the additional time that is added to the countdown timer on passing a checkpoint. I've never seen details published - until now....

Here's a table that shows the time, in seconds, that is added to your overall counter per stage. The rightmost route is show first. The DIP switches of the arcade cabinet can be set to four difficulty settings for timing, and each respective setting has its own column. If you are lucky enough to find a working cabinet in the wild, it's easy to determine the setting by looking at how much time you start the game with.

.
         | Easy | Norm | Hard | VHar |
         '------'------'------'------'
Stage 1  |  80     75     72     70  |
         '---------------------------'
Stage 2a |  65     65     65     65  |
Stage 2b |  62     62     62     62  |
         '---------------------------'
Stage 3a |  57     55     57     57  |
Stage 3b |  62     60     60     60  |
Stage 3c |  60     60     59     58  |
         '---------------------------'
Stage 4a |  66     65     64     62  |
Stage 4b |  63     62     60     60  |
Stage 4c |  61     60     58     58  |
Stage 4d |  65     65     63     63  |
         '---------------------------'
Stage 5a |  58     56     54     54  |
Stage 5b |  55     56     54     54  |
Stage 5c |  56     56     54     54  |
Stage 5d |  58     56     54     54  |
Stage 5e |  56     56     56     56  |
         '---------------------------'

To be honest, some of the entries are a little strange. For example, why is Stage 3a (Cloudy Mountain) more difficult on Normal than Very Hard? Is this an error in the table?

I'm working from the Overseas version of Outrun. I'm not sure yet whether the table differs for the Japanese version where Gateway has been moved to Stage 4.

It should also be pointed out that all the tracks in Outrun are the same length from a technical point of view. Obviously some will be tougher in terms of sharp bends and thinner stretches of road. The road split at the end of each level is hard coded and not read from the level data.

Moving onto the traffic in the game. Once again, this can be set by the DIP switches to four independent settings. I haven't reverse engineered the traffic code in detail yet, but I can provide some rough guidance as to how the settings affect each level in the game. It's my understanding that the following table represents the maximum number of vehicles that can be spawned simultaneously on each level.

.
         | Easy | Norm | Hard | VHar |
         '------'------'------'------'
Stage 1  |   2      3      4      5  |
         '---------------------------'
Stage 2  |   2      4      5      6  |
         '---------------------------'
Stage 3  |   3      5      6      7  |
         '---------------------------'
Stage 4  |   4      6      7      8  |
         '---------------------------'
Stage 5  |   5      7      8      8  |
         '---------------------------'

Looking at the code which spawns the traffic, hacking the game to support more traffic wouldn't be trivial because there are only 8 slots in the jump table reserved for traffic sprite routines.

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