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Atari: 80 Classic Games in One! contains two unused ROMs created to test the emulators used in the compilation. Interestingly, the .txt file that contains the descriptions of all the featured games also has explanations of what these ROMs are, suggesting that they may have at one point been planned to be included as bonus content on the compilation for regular players:

"[colours]
What is this?
This ROM was created as part of the development
process for ^RAtari 80 Classic Games^0[sic]. This ROM
was transferred into a genuine first generation
Atari 2600 (bought by the lead programmer's
family back in 1977!) via a Cuttlecart. It cycles
through all the available colours in the Atari
2600 palette, displaying the colour's number as a
binary "bar code" at the top. The output of the
Atari 2600 was hooked up to a video capture card,
and each frame was digitised and its colour ID
determined by reading the bar code on the image.
All frames of the same colour were then averaged
together to get an average "RGB" colour value for
that number. This process was used to get accu-
rate colour matches with the original Atari 2600.
[sound]
What is this?
This ROM was created as part of the development
process for ^RAtari 80 Classic Games^0[sic]. This
ROM was transferred into a genuine first gener-
ation Atari 2600 (bought by the lead programmer's
family back in 1977!) via a Cuttlecart. It plays
a sound sequence consisting of a one second low-
volume beep, 1 second of silence, and then 4
seconds of a particular Atari 2600 "voice",
followed by another 1 second of silence. Each of
the available voices is played in turn at a
preset frequency. (Once all voices were played,
the frequency would change and the process would
repeat.) The output was captured via a PC's

^G(more...)
Page 2
^G(...more)

sound card and a program found the sound's
fundamental pattern. These captures were used
to generate accurate sound matches with the
Atari 2600.

Note: The left difficulty must be in the B
position for the sounds to start."

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