Topic: Scramble inaccuracy - looking for some history...

I have had a look at a number of FPGA ports of the Arcade game scramble and presumably they are all derived from a single source base.

The problem is none of the implementations seem to have a visible front laser or laser sound effects. Plus, as far as I can tell they all use a single fire button when the original game used separate fire and bomb buttons.

Here is a video of the game as I remember it

And here are examples of two FPGA implementations where you can see the bombs but no laser though the laser does fire you just can’t see or hear it and it is tied to the bomb button.

I am looking for some history on the original implementation, why this is the case and most importantly can it be fixed (which I will try to do if I can)?

Finally am I the only person old enough to have noticed this?

Re: Scramble inaccuracy - looking for some history...

About history of the buttons:

I checked Mikes original release from 2007 (, it already had separated inputs on the core but mapped to one button:

  -- assign inputs
  ip_1p(5) <= not button_debounced(5); -- shoot1
  ip_1p(4) <= not button_debounced(5); -- shoot2

This core implementation of Mike on an Spartan 3E dev board, the readme.txt shows this connectivity and a remark:

     Switch1 is Shoot/bomb "
     Not great control mapping but enough to play with.
     I expect users to remap the controls to expansion connectors of their choice.

So for this board there was no other way as the #buttons/switches were limited. Later on the use of standard "Atari" joysticks (I assume most people use) limit a proper/better setup as well - as these only have 1 fire button...

So with proper input hardware (= supporting two separate fire buttons) it could be fixed, I'd say.

Oh, for reference to original stuff I'd (only) look here: … me_id=9447


Re: Scramble inaccuracy - looking for some history...

Thanks for the reply.

Stupid me, as a classical programmer I should have checked the source first before posting but I had it in my mind this was a bug which it sort of turned out to be – just not in the VHDL.

After I rebuilt the code with the aim of getting a starting point to modify the fire and bomb buttons I discovered, prior to making any code changes, that the missiles where visible.

I have a few FPGA boards (including a FPGAArcade) and I had just used loaded one of the pre-built cores. I had also looked at videos of the emulation running on a different boards and they all had the same problem (invisable missles) so I thought it was a bug. Also because everyone was using a single fire button I thought it had been coded that way.
Anyway, I built the bit stream from source using the correct ROM i.e. as per MikeJ’s SHA1 checksums the missiles worked fine (google Current MAME versions of the ROMS do not work.

So I am just about to try two fire buttons!

BTW, MikeJ is my hero for his efforts on this.

Re: Scramble inaccuracy - looking for some history...


I modified the code and two fire buttons work fine.

That and using the correct ROM version fixed my problems.