Missile Command Multigame    -- Trouble shooting guide

The most common issues with the Missile Command Multigame have been either incorrect installation or general Missile Command board problems. The Multigame kit can only work on a fully functional Atari Missile Command board.

Common mishaps during installation include installing the kit in backwards (eg. pin-1 orientation reversed), or not pushing the kit entirely into the socket. The best thing is to review the installation instructions

There are two notable software bugs with the multigame kit. Both have been fixed and depending on the software release you may or may not have seen the issue. Also both have simple workarounds.

BUG 1: Large Trak-Ball versus Mini Trak-Ball

Trak-Ball not behaving the same as before the kit was installed?

Missile Command supports both a Large Trak-Ball and a Mini Trak-Ball. The setting is controlled by DIP #4 at pcb location R8. There is a bug in the multigame software version MCM001A where the DIP setting would get ignored under certain conditions and the trak-ball could behave differently than expected.

Workaround: If you are seeing this issue with release MCM001A, here is a quick and easy workaround. Enter setup mode and scroll down to "save and exit" and press fire. This will cause the settings to be saved. And that is enough to cause the multigame software to start repecting the trak-ball DIP setting.

The bug is that until the settings are written to the non-volatile storage, the trak ball DIP setting is ignored. This bug was fixed in release MCM001B.

BUG 2: Bonus or Cities settings do not match gameplay

Have you gone into setup mode, changed the settings for starting cities or bonus cities only to find out when you play the game the settings dont match?

There is a bug which was inadvertantly created when the fix above for the trak-ball was introduced. Workaround: If you are seeing this issue and have release MCM001B or MCM001C. And your racking your head against the wall on why it is not working, here is an easy workaround (thanks to Brian Olson of CA). For the settings to work correctly the real DIP settings for Bonus and Cities must be set to the factory default. This means DIP #1,2,5,6,7 at pcb location R8 must be set to "ON". This corresponds to bonus city every 10,000 pts and game starts with 6 cities. NOTE: this is just how the DIPs need to be set. Once the DIPs are set this way the setup menu options will now correctly work.

The bug is that real DIPs where inadvertantly being combined with the setup menu settings and the combined result in some cases was totally differently than what was expected. This bug was fixed in release MCM001D.

What if I have a MC Cockpit?

Are you one of lucky few that own a rare MC cockpit? If so, you're well aware there is no P2-START button. This means you cannot switch games and cannot enter setup mode. Doh!

As of release MCM001C, the multigame will now accept P1-START and LEFT FIRE as an alternate button sequence to the original P1-START and P2-START. So you can use either sequence to switch games and to enter setup mode. You will need release MCM001C or later.

Pressing P1 + P2 does not switch games

Make sure you dont inadvertantly have the multigame configured for "MC MODE" in the Super Missile Attack difficulty setting. See settings for more information about this sometimes confusing setting.

Game is "streaking" leaving pixels behind

This is most likely a power supply issue. Check that the +5v is indeed +5v. The kit seems to be more sensitive than the original boardset to the +5v line, and when the +5v drops to around 4.7V, some strange "streaking" can sometimes be seen. It should be noted the original boardset without the kit will do the same thing, but it the original game seems to not fail until closer to the +4.6 or +4.5 voltage range. The multigame kit seems to be more sensitive to low voltage than the original game. I hope to someday have some pictures of this streaking.

General Missile Command trouble shooting guide

As with most Atari games of this era, the first thing to do when a game is not working correctly it to put the game in selftest mode. Refer to the manual on where the selftest switch is located.

Game is dead. Testmode only pulses out a series of beeps

The first thing MC will do in testmode is a RAM test. MC uses 8 DRAM chips that are 16K x 1-bit. The RAM test fully excercises the first 512 bytes of the DRAM and if that test fails, it attempts to identify the failing and passing DRAM chips by looking at the failure data. It then takes this data and converts it into a series of pulses to indicate which chips seem good and which chips seem bad. The test uses a low tone for good and a high tone for bad. The codes are shown in the table on the right.

It has been seen that MC can sometimes do a poor job of identifying the failed DRAM chip(s). While the test over the first 512 bytes is very thorough, it stops after the first failure which can lead to misleading results. Also the design of the DRAM circuit is lacking pullup resistors on the DRAMs. This means a failing DRAM what is not driving its output will leave that data bit floating which also contributes to misleading data. It should be noted if the selftest does not pass the RAM test, that there is a very high chance one more DRAMs are bad, however, it may not correctly identify them.

The Multigame selftest improves the identification logic and performs additional testing to more accurately report the good DRAMs versus the bad DRAMs. The Multigame also will test the entire 16K bytes versus just the 512 that the original MC selftest does. The result is improved fault identification. The Multigame sefltest also uses both audio and visual indications to pulse out the pass/fail DRAM codes. The screen will change colors, Green for pass, Red for fail while the tones are being pulsed. The original MC tones are also preserved. Low tone indicates a good DRAM, high tone indicates a failed DRAM.

Beep Number Suspect BAD ram chip
1 (D7)P4
2 (D6)N4
3 (D5)M4
4 (D4)L4
5 (D3)K4
6 (D2)J4
7 (D1)H4
8 (D0)F4

Sounds are wrong (or missing)

Missile Command produces sounds using a single pokey chip (40 pin IC at chip location N/P/8/9 near the DIP switches). The pokey chip usually has the text "CO-12294" on it. The pokey chip is a custom chip made by Atari.

If the sounds are incorrect, distorted, it is possible the pokey chip is bad. If you have no sound at all, it could be the pokey, it could be the audio pre-amp on the board, or it could be the external audio amp on the AR II board.

The standard Atari Missile Command selftest will perform a simple pokey diagnostic and report the result. A failed pokey is indicated on the upper left side of the screen with the text "CHIP BAD". The diagnostic only tests the random number generator function of the pokey, but it does provide some indication if the pokey is bad.

The Multigame sefltest performs the same random number generator test on the pokey, but the results are indicated in a different place on the screen.

Pokey chips are used on many classic Atari gameboards including Centipede, Millipede, Asteroids Deluxe, Missile Command, Crystal Castles, and many more.

Replacement Pokey chips are available from several sources such as Mike's Arcade.

Missile Command test mode screen
showing faulty Pokey

Multigame test mode screen
showing faulty Pokey