[stella] Clones

Subject: [stella] Clones
From: Thomas Jentzsch <tjentzsch@xxxxxx>
Date: Sat, 7 Oct 2000 18:44:24 +0100
i was always wondering, how many real different games
where programmed for the 2600. When i downloaded a file
with more than 1400 different roms, i decided to
find out.

I wanted to let my PC help me. So i wrote a little
Borland Pascal program which compares rom-dumps. This is
done by a pseudo dictionary-based compression, which
finds duplicate code or data fields. Each rom is
compared against all other ones, and when i shows some
relationship to another rom, the later is also compared
against the first. This gives two compare values, which
are written into a text file.

Before i started the test, i removed all multipack-dumps,
test and simple demo roms and finally counted 1075
rom-dumps. The result is in the attached

The ListSpy-program shows the txt-file as lot of
matrixes where similar roms are grouped together. The
coloured (red..yellow..green..blue) numbers show how
similar two roms are. All rom-names were created by
good2600 v0.9994.

Though these tests are far from being perfect, they
should help to get some answers about the history
of those roms:
- which original rom was used for a clone/hack?
- were has code been reused for different games
(Brick-Kick and Pac Man, Mythicon)?
- how big are the differences between PAL and NTSC
- how different are versions of the same game (Dodge
- are some suspected games really clones?
- does an oversized dump also contain another rom
(Combat - Tank Plus)?

Most informations are only statistical, but they give a
hint where to start (disassemble).

What do you think about it?

Attachment: CloneSpy.ZIP
Description: Zip compressed data

Current Thread
  • [stella] Clones
    • Thomas Jentzsch - Thu, 26 Oct 2000 00:58:35 -0400 (EDT) <=
      • <Possible follow-ups>
      • tjentzsch - Sat, 28 Oct 2000 11:43:24 -0400 (EDT)