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Space Invaders Multigame - Powerup Self test

When the game first powers up, it performs a series of selftest diagnostics to insure the game is operating properly. This kit can also be a useful tool for debugging broken boardsets.

The first thing the kit does is in an internal checksum of the code eprom which is contained on the kit. If the checksum fails, the kit cannot continue. It will attempt to display a rom checksum failure message on the screen and after a few seconds, the game will reset because of the watchdog reset circuit will repeat the powerup selftest. A eprom checkum failure usually indicates a problem with the kit itself.

After the eprom checksum test passes, the kit performs an extensive Dynamic RAM test. The test writes various patterns (accounting for aliasing), with various hold times to increase the DRAM coverage. If the ram test fails, the diagnostic then performs additional testing to narrow down and isolate the suspected failed ram chips. During the memory test, you may see patterns on the screen that look similar to those below.

 

memtest patterns

memtest patterns

memtest patterns

memtest patterns

memtest patterns

memtest patterns

If the memory test passes (normal case), the selftest will continue on to other hardware tests.

If the memory test fails, the software will pulse out a series of sounds indicating the FIRST bad RAM chip location. This is very similar to how Atari selftests function. That is, the number of "beeps" indicate the first suspected chip. That chip then needs to be replaced, and then the test rerun to identify any other faulty chips. Again, this test only indicates one chip failure at a time. It should be noted that these types of memory tests are not a 100% guarantee that the identified chip is indeed wrong. In some cases the problem can also be broken traces on the boardset, or problems with other chips (eg. drivers, buffers, etc...). So use it as a guide.

When the memory test fails, a few seconds later after the chip code has been pulsed out, the game will reset because of the watchdog reset circuit and the powerup selftest will repeat. The table below is used to map the number of "beeps" (missile shot sounds) to the suspected bad memory chip.

 

Beeps Chip
Location
Beeps Chip
Location
1 G8 9 H8
2 G9 10 H9
3 G10 11 H10
4 G11 12 H11
5 G12 13 H12
6 G13 14 H13
7 G14 15 H14
8 G15 16 H15

selftest

testmode

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