Game Killer

Game Killer Screenshot
Technical Info
ROM	8 kbyte
Hardware features	1 Button Freeze
Manual	JPG: 01 pages
CRT ID	00
Control Registers	$DE00/DF00 (likely all IO1/2)
Programming	LDA #$00 STA $DE00 STA $DF00 ; disables cart
	Cart is enabled by the cartridge button and on powerup

The adverts found for this rather rare cartridge which was only available in the UK as of current knowledge contain the words:

WARNING: It is possible that some of the games you own will not have all the levels and screens promised by the software houses. This could mean that you could send them back due to false information under the Trade Description Act.

and is somehow funny wording since the rest of the advert just mentions that the cartridge is a revolutionary survival kit, disables sprite collision and for the interesting part start your game where you want!.

The company behind this advert just renamed from Robcom to ROBTEK as the advert states. Robcom was previously selling modems mainly. The change on the company name came with the introduction of the Game Killer cartridges if we can trust the adverts. Publisher Information at Amiga Hall of Light also notes ROBTEK as the company behind a few games.

Game Killer Cartridge

On powerup a real intro pops up. It is packed with MC CRACKEN COMPRESSOR 1.3 and includes a scroller reading:

Copyright (c) M.F.Zonnefeld/P.A.Share - ROBTEK 1986. Graphics by J.W.A.Kampstra. Music by R.Hubbard. Exclusively licensed to MASTERTRONIC Int. for America, Canada and Australia under the name 'INFINITY MACHINE'. Manufactured by RAM ELECTRONICS....GAME KILLER gives you the advantage over you computer. Break through your game with ROBTEKS GAME KILLER.....HIT SPACE TO CONTINUE....

This article from Zzap! also notes the tune by Rob Hubbard and this excellent article at Commodore Zone about Rob reads:

In 1986 the company Robtek marketed a new product called Game Killer for the Commodore 64. It was a cartridge-based device that allowed gamers to cheat when playing certain games that contained sprite collision code. The cartridge would allow the sprite collision to be switched off, which in effect meant that you could complete a game because the in-game enemies could never kill your character!

Unfortunately it did not work that well as it was only useful for certain games due to the software method used.

Robtek asked Hubbard to compose the theme music for the software. It was the only commercial software utility that contained a Hubbard soundtrack and what a soundtrack it is! It’s actually a remix of some music he did for the Human Race (Mastertronic 1986).

It has a memorable chorus line, which you won’t easily forget, it’s one of those tunes that just seems to stay in your head even after all these years - I can still hear the tune now! As usual it complements the software well and is most appropriate.

Commodore Horizons Issue 27, March 1986

Game Killer Cartridge

The Zzap! article and the package are also explaining the only functionality of the cartridge being achieved by pressing the cartridge button alone or while holding the joystick pushed up or down to diable sprite/sprite, sprite/background collision or both. Along with an option to enable said collisions again a real Killer to many games. Commodore Horizons Issue 27 published some quick docs (see right) which slightly differ from the Zzap! article.

Game Killer Advert March 1986

Game Killer Advert May 1986

Tech

Game Killer _just_ made it into this wiki and the category Freezers due to it really applying the techniques required - on a very basic level. A quick disassembly on the routine taking over the collision hunting and disabling shows a first weakness:

• Zeropage address $44 will be trashed by the cartridge - it is being modified before some work area is moved to the stack (including $44 again).

The following comes from gamekiller.c from the VICE emulator:

ROBTEK "Game Killer"

- 1 8k ROM
- when cartridge is active, ultimax is enabled when addr>=e000, so the
  rom is visible at e000, below is normal c64 ram
- the code writes 0 to both de00 and df00 to disable the cartridge. we
  assume the cart uses the full io1 and io2 range
- when the freezer button is pressed the cartridge will be enabled and
  an NMI will be triggered

Binaries

Game_Killer_binaries_rr.c64.org_2010-04.rar contains just the C64 binaries:

• Game Killer bin and crt
• standalone prg "intro" of the cartridge with Rob Hubbard sound
• Rob Hubbard Cracker_Mix.sid tune

Game_Killer_all_rr.c64.org_2010-04.rar contains:

• all of the above
• High quality package inlay
• Manual Sheet

Many thanks to TNT/Beyond Force for this special ROM dump and the scans!

Trivia

• As it seems the cartridge was not an overwhelming success and sales quickly were stopped. Advertising apparently was stopped after a very short time and likely only cartridges of a first and final production run were sold. A quick look at the market before said production run might have saved them from doing it at all since the competition was already going strong at that time.

Weblinks

• Game Killer at Commodore Info Page
• Nightfall Crew Blog found the Game Killer and Expert Cartridge
• Rob Hubbard Article at Commodore Zone mentions Game Killer here
• Retroport.de