There was a special breed of programmers and game designers nurtured in the cradle of Williams Electronics at the turn of the 80’s.  Two of the stand-out stars from the Defender arcade project were Eugene “Dr. J” Jarvis & Larry “Kid”  DeMar.  They weren’t just working for a paycheck, game design was a deeply personal and passionate undertaking: Meticulous and thought-out extensions of their own wild musings of technical genius, coupled with a child-inspired fascination with engaging the public through exciting electronic adventures.  Their quest put them together for an epic feat of gaming excellence called Robotron: 2084, sealing their legacy in the world of coin-op—These were the Vid Kidz!

Proving that the passion for gaming runs deep in the veins of the Vid Kidz, here is an example of an extra-special patch put into the cocktail Robotron machine given to Larry’s parents.


At the time Robotron was “new” in the arcades of 1982-83, the Twin Galaxies scoreboard was engaged heavily with a competitive youth who were striving for high score superiority on both Defender and Robotron.  But Robotron had a pop-culture mystique unrivaled in the arcades, so the champions of the day became legends of the arcade.  If you wanted to be known as an endurance marathoner, then there was no choice but to be great at Robotron.

The last code updates to Robotron were done in 1982, as the blue romset offered cocktail mode, and a few internal fixes including a wave 1 “bozo” setting to make the first wave easier for flailing NOOBs.

The code went untouched for another 5 years until 1987 when a young genius out of Canada offered up a handful of coding fixes after reverse engineering the source code from a rom dump at an arcade. Christian Gingras brought about a fix for the dreaded, “sideways Enforcer explosion along a vertical wall” glitch which triggered a reset of the game….the Carpet Pattern Reset!  Larry coded the fix and Eugene offered up the romset when a company named Digital Eclipse planned a Williams compilation release for PC. The same romset which made it into the Xbox 360’s version of Robotron.

Fast forward another 25 years to the summer of 2012, nostalgic players are once again reveling in the chaos of Robotron and playing long games.  June marked the 30th anniversary of the game, and what a great summer it was for celebrating the classic robot war.  Both Larry and Eugene were celebrated through arcade parties at Star Worlds Arcade near the home of Robotron, Chicago, IL.

By 2013 the “100 Million Point Gauntlet” Endurance challenge was crafted to challenge players at attempting 100 million points on 1 single credit (Twin Galaxies in 82-83 allowed the player to restart games and add scores for a cumulative total).  Players like Ken House, Dane Tullock, and David Gomez stepped up to the dual joysticks, and eventually Ken House toppled the 100 million ceiling after 23 hours of continuous gameplay, winning himself a Robotron Gauntlet T-shirt and a custom control panel.  These challenges did not go unnoticed, being watched with interest by Larry DeMar on the Twitch TV streams of the “enduros.”  During Ken’s original session it was discovered that at 100 million points Robotron shared the same Goldilock zone/extra-life bonanza as Defender did at 1 million points.  A revelation undiscovered and undocumented in the code for 32 years, even unrealized by the original programmers!  By the time David Gomez was proving his own worth reaching 125 million points, Mr. DeMar had an idea!…update the romset to cater to the long-game players.

His associate Duncan Brown pulled the Vid Kidz Development environment out of dusty storage, and Larry got to work.  The 10 million digit was unmasked (originally masked for Stargates allotted screen space), a life counter was added, and a few other changes were made.  By November a beta team was assembled to test the new romset (aptly coined Tie-Die, as a nod to Jarvis’ wild Hawaiian shirts and Robotrons ability to kill off the player).


Sean Riddle, Dave Langley, David Gomez, Ken House, Dane Tullock and Mark Hoff put the romset to its’ paces on MAME, upright machines with real hardware, and even cocktail machines.  Passed with flying colors the romset did!

If you are already running the Blue romset in your real Robotron machine, only a handful of the chips have to be swapped out in order to use this update.

And we are proud to announce that “The Game Preserve” in Houston, TX (Home of Robo-champ, David Gomez) will be the first authentic public arcade offering this exciting new challenge to the public.  Come join the fun of a new era of Robo-competition!


November 25th, 2014 – Larry –

I’m ready to test the new version of Robotron.
The new work changes 5 Eproms from the blue romset:   4,7,8,10,11 (and rom 5 for the enforcer explosion “reset” bug)

2-16-15 Clarification from LED: My “shot-in-the-corner” fix only affect Rom 5 and I included my version of Rom 5 in the romset (not further modified for Tie Die). My Rom 11 (equivalent to B) does not carry any changes from Blue other than Tie Die.

The changes are:
1) Number of Lives shown at bottom of screen for each player (they still wrap at 256)
2) 10 Million digit now shows
3) 10 Million+ scores are correctly placed in High Score table which goes up to 9.999.999
4) Extra Ships now settable at 10-15-20-25-30-40-50-60-70-75K
5) Set HSTD initials to “4” to start game at 99,900,000 to see Goldilocks mode.  Will not register as HSTD
6) If 3 blanks entered for initials then score is not entered into the High Score Table
7) Default initials changed for entries 3, 4 an 5


Sean Riddle 11/25/14 – Larry- So far no problem here on my machine, although I’m not that great of a player.  Goldilocks mode is a lot of fun.
I’ll let you know if I see anything odd.
11/26/14 – I ran JROK’s board with tie die and as expected it worked fine.
11/27/14 – I played several 1 and 2 player games on the cocktail machine and everything looked fine.

David G. – Had a good game, played to 12.5 mil and stored 100 lives.
It’s really nice to have the lives counter available, but it can also sort of act as a hindrance and distraction if you get fixated on it (like I did!). It completely eliminates the guesswork involved from rolling lives, just watch out during the Goldilocks zone, which could put your lives count over the top real quick!  This romset is the future of Robo competition. A big thanks to Larry DeMar for making this happen!

Dane testing up to 10 million- TWITCH

Mark’s beta testing- 40 waves, Goldilocks zone, Difficulty 10.

Larry quote- On why a score over 10 million registers similar to how Joust would list it. Previously the player had to stop at 9,999,975 to take top honors on the scoreboard.  “The 9,999,999 score is intentional.  It’s really the right way to handle  the placement of an 8 digit score in a table that only holds 7 digits.”

Setting High Score Initials to 4 for Goldilocks zone – Larry –

The Goldilocks hack is checked for when the “lives” message(s) is displayed.  If the HSTD initials adjustment is 4 and Player 1’s score is zero then player 1’s score is updated to 99,900,000.  The lives message doesn’t appear until after the copyright message has finished.  If you shoot anything before this happens you don’t get the free points.
When HSTD is set to 4 you don’t get to enter your initials regardless of whether you received the free points or not.   A grunt can kill the Goldilocks points.  It is a check of Wave 1 and Player 1’s score.
It was patched in as few bytes as possible (free space is very tight in the roms), so only player one is affected.  Also, it is dependent on zero score when the new “Lives” message is posted so if you hit anything while the copyright message is showing then you won’t get the free points (and still not be allowed to enter your score in the HSTD).  It’s there to give people the opportunity to see this aspect of the game, so no points for player 2.

Ken House – Larry, I love you man!

Larry on some rom patch history –

The diagonal explosion bug got lost and published among a problem with the original blitter chips where early prototypes (or maybe the development logic boards) would occasionally crash the game.
This went all the way up to production when the final chips fixed a discovered problem with the ram to ram problem but of course not the diagonal explosion bug (which was my code that was looked at during this time and I’m embarrassed to say that I didn’t find the problem then).  We assumed that the diagonal explosion thing which had been seen was part of this.
We put in the adjustment to get rid of all ram to ram operations as a safety net which most noticeably to the player and operator was the attract mode logo screen balls.  It also turns horizontal explosions into vertical ones, but the flawed diagonal ones still persist with this adjustment.

Dave Langley 11/29/14 – After a really hectic week at work I finally found some time to burn ROMs and fit them to my cocktail this afternoon.
Initially after fitting the ROMs I was getting Error 2-0-4, so I put the original ROMs back and the game was fine, re-burnt ROM 4 and still the same, then I realised that I had Pause ROMs fitted, after replacing ROM 12 with a stock Blue label ROM it all jumped into life!
(Just putting this here in case anyone else gets it as it wasn’t immediately obvious).
So onto the gameplay:
Set high score initials to 4 and dived straight into goldilocks mode on a single player game, awesome.
I love the lives display at the bottom but I also find I’m watching it and gauging my performance by it, previously I’d have judged my performance on my waves per 100k of score count.
There seem to be no issues in cocktail mode  ….
Anyway, thanks for the awesome code Larry, looking forward to playing it some more later.

Mark Hoff:
and the most important question of all, Larry, what color romset will you christen this 2k14 update? blue and patched blue is already taken in the street lingo. E would probably go with “tie-die”. what say ye? – November 20 at 12:37pm
Lonnie McDonald:
Love it – November 20 at 1:06pm
Mark Hoff:
subconscious typo? it is tie-dye isn’t it.
but tie-die sounds much more appropriate for robotron. ha ha – November 20 at 1:18pm

Larry 12/12/4 – I made Tie-Die by doing object code patches over the existing code and using tiny pockets of free space. It is the same method that Christian Gingras used to fix my hideous bug (which I’ve incorporated in the new rom set).

Release Info from Larry, Jan. 2015-  “There’s no hurry to release it other than to marathon players. It looks like a Twitch-type event is being planned for the end of January so I’ll consider that the final checkout and aim for an early Feb release.”
  • The 2nd Robotron 100-Million Point Gauntlet was held at TwinGalaxiesLive which was considered the final Beta test for Tie-Die.  Summary of the event was posted at

TIE-DIE OFFICIAL RELEASE DATE- posted at on Feb. 9, 2015.  See email below

  • Gary- You are clear to release the tie-die Rom images.  It should be “V2” which will have the factory default difficulty of “3”.
    Thank you for letting me take the time to make sure we were ready to go. -Larry

Larry Explains the Development of the Tie-Die Romset: Youtube

Larry DeMar (1-31-2017) There was significant time between the making of Tie-Die and the making of the video.  I shot the video in a single uninterrupted stream and did not remember (during filming) that I actually had to add a new function called HEXBCY (rather than correcting HEXBCD).  I needed a 3-digit conversion of the longer number returned in the 16-bit Y register rather than the 8 bit-A register that could only return values up to 99.  The bug (never fixed in HEXBCD) carried into the new HEXBCY and was fixed there.  That’s really the reason the new code is much longer, not just to fix the bug as I indicated on screen.

TIE-DIE EPROM LABELS by Johnny Gallegos (DivingBuddy on KLOV)

    • I used Adobe Illustrator and Microsoft Publisher to create the design layers. I used standard full page label paper to print the labels. I resized the image to fit in top of the eprom.
    • Using length at 29.8 mm and the width at 11.2 mm will fit on the eprom chip with no overlap.
    • MS Publisher Document zipped- Tie-Die-Robotron ROM Label Rev1
    • PDF link- Tie-Die-Robotron ROM Label Rev1
    • JPG image-

Tie-Die-Robotron ROM Label Rev1

Variation on Labels from Nan Gomez-


New to Robotron?  Click HERE to get started learning how to play this golden age masterpiece!
  •  —–> More MAME Info at THIS link <—–


  • DOWNLOAD image courtesy of WindDrake on KLOV
  • Should work on any JROK WSF 1.x Board.
  • This was made from the last revision of the WSF 1.x ROM (AFAIK), 1.11.
  • You can write it to any standard 8Mbit EPROM. 27C801, 27C080, etc. Must be 100ns or faster.

Per James (Feb 2015)-

  • Correct order is….
  • Menu @$000000
  • Defender (red) @$010000
  • stargate @ $020000
  • Robotron @$030000
  • joust @ $040000
  • bubbles @ $050000
  • splat @$060000
  • sinistar @$070000 ( Note: $7D000-$7E000 is also blank )
  • blaster @$080000 -> $0B0000
  • sinistar (AMOA) $0C0000 ( Note: $CD000-$CE000 is also blank )
  • Defender(white ) $0D0000

Promotional flyer created for The Game Preserve by Stephen J. Silver


What could possibly be more exciting than having the Vid Kidz themselves installing the new Tie-Die romset in your machine!

Per Larry DeMar on 12/12/15:

I was at Galloping Ghost Arcade this afternoon for Doc Mac’s “Narc” event.  It was a nice reunion of the gang.

While I was there, I updated the eproms in their Robotron to tie-die.  I thought it would be worth adding Galloping Ghost (Brookfield Illinois) to your tie-die page.  I’ve attached some photos capturing the process.


          Photo Dec 12, 5 36 05 PM                       Photo Dec 12, 5 37 21 PM
Photo Dec 12, 5 31 30 PM     Photo Dec 12, 4 48 18 PM
                                                                                         Left to right-Warren Davis, Todd Allen,
                                                                                         Mark Loffredo, Eugene Jarvis, George Petro
                                                                                         and Mr. Big and Larry DeMar in the 2nd row.

Rom board from David Gomez’s Robotron machine used to reach 150 million points on 1 credit in January 2015.

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