Sky Kid (NES)

Sky Kid
Developer: Namco Publishers: Namco (JP), Sunsoft (US) Bandai Namco (EU/AU) Platform: NES Released in JP: August 22, 1986 Released in US: September 1987 Released in EU: June 18, 2020 (Namco Museum Archives Vol. 1) Released in AU: June 18, 2020 (Namco Museum Archives Vol. 1) This game has hidden developer credits.

Sky Kid is the story of a bird who flies in a plane bombing buildings causing mischief.

Developer Credits

At $0071E0 in both versions, there is a copyright string, along with the name of the programmer:

COPY RIGHT 1984 1985 NAMCO LTD,
ALL RIGHTS RESERVED
MR HIROKI AOYAGI

CRC Test

There are a series of Namco games, made by the programmers Haruhisa Udagawa and Kumi Hanaoka, that contain the same self-test for the data integrity for (Babel no Tou, Dragon Buster, Family Jockey, Lupin Sansei: Pandora no Isan, Mappy-Land, Pro Yakyuu: Family Stadium, Sanma no Meitantei, Super Xevious: Gump no Nazo, and Valkyrie no Bouken: Toki no Kagi Densetsu).

To enable any of these tests, you need a special device that should be plugged into the expansion port. The operation of that device is very simple. It should accept the data bit from the data input port and return it back inverted to the output data port. The device consists of a 4-bit shift register, working as some sort of FIFO buffer. The input bits are shifted to the output after 4 cycles.

At the game's boot, it tries to send some special data to the device. If the data output doesn't match the data input inverted, then the game continues the normal operation. But if all data (usually 32, rarely 64 bytes) matches, self-tests will be performed. The program calculates 24-bit partial checksums for the PRG (excluding the last 8K) and the CHR data, summing only every 15th byte, and comparing it against the etalon.

Before testing of the PRG data, the background color turns red, before testing the CHR data, it turns green. If any of these tests fail, the program will jump directly to the reset routine. It means, one of these tests will be performed infinitely, until the special device is unplugged, or until the test passes.

Normally, you'll see the red to green flash just before the game's boot. Or the static red screen if the PRG data is bad, or the flashing red to green screen if CHR data is bad.

Using this Game Genie code GEONVTEI, you can skip tests for the special device presence and jump straight to the integrity tests.