Moon Cresta seems to be one of those games people either love or hate.  I've fond memories of playing it in a hotel bar in Scarborough (North East England) back in the early 1980's so I think it's a pretty cool game.

It was never on my list of games to hack, but a throw away comment by Jase on UKVAC a couple of weeks ago about a high score save kit got me interested.

I've already made the modifications to the high score saving code (it wasn't too hard as the game already has a high score table and name entry routine) so it was just a case of copying them to and from NVRAM.  Not having a boardset (yet), I haven't confirmed this works so it's not ready to be released, but hopefully will be in the next couple of weeks.

Whilst doing the high score save hack I noticed it's another game with annoying freeplay mode, where it sits at the "press start" screen rather than going through the attract mode.  I decided to also do this modification (and been able to test in Mame) which is what the code below is for.  Basically when in freeplay mode, it still displays "free play" on the screen, but now cycles through the attract mode.  Just pressing P1 or P2 start, begins the game.

The hack has been done for the "mooncrstuku" ROMset, and as the addressing is different across different variants it will only work with that one.  The code itself is simple so could be adapted to the other ROMs by changing the absolute addresses, so I've also included the source below.

Changes to be made:-

ROMset mooncrstuku

ROM smc1f

#0030 3A 00 B0 E6 0C FE 0C C2 4D 01 3A 35 80 B7 C2 4D 01 3A 00 A8 CB 47 3E 01 20 0A 3A 00 A8 CB 4F 3E 02 CA 4D 01 32 32 80 C3 81 01

#00F4 C3

#0115 30 00

ROM smc6f

#2FCE (individual ROM address #07CE) C9

Source code

; enhanced free play @0x0114
call freeplaycode    ;intercept for hack @ 0x0030

freeplaycode: ld a,(0xb000) ; are we in free play mode?
and 12
cp 12
jp nz,0x014d     ; return to main code if not
ld a,(0x8035)
or a
jp nz,0x014d     ; don't add dummy credits if already registered
ld a,(0xa800)
bit 0,a              ; P1 button pressed
ld a,1
jr nz,addcredit
ld a,(0xa800)
bit 1,a               ; P2 button pressed?
ld a,2
jp z,0x014d       ; return to main code if not
addcredit: ld (0x8032),a    ; add 1 or 2 credits depending on P1/P2 pressed
jp 0x0181          ; return to main code

; 0x2fce = RET (C9)   ; don't jump to static screen
; 0x00f4 = JP (C3)    ; don't jump to static screen

I've posted this up on UKVAC as the board has evolved, but here's a bit of a summary of a single ROM/RAM board I've made for a number of Z80-based games.

At the end of last year I was repairing a load of Galaxian boards, some original, some boots, and found a lot of problems seem to be with the ROM daughterboard (which often goes missing) or the program RAM, so I wanted to design something to make troubleshooting a bit easier.

Buying the already-available single ROM boards for a number of games I own would work out pretty expensive, so I spent some time in January designing my own single ROM/RAM daughterboard that plugs into the Z80 socket and replaces the old ROM board and RAM (RAM is optional).  You just need to burn whatever version of Galaxian or clone onto a single chip, choose whether you want to use separate RAM or not and install it if you do, then remove the Z80 and plug it into the daughterboard.  Once this was working, it was time to extend to other games.

So rather than it just being dedicated to Galaxian, I tried to make the hardware as generic as possible.  The memory addressing for the ROM and RAM is handled by a GAL, and I fed multiple memory address lines plus various control signals into the GAL, so the board isn't restricted to just Galaxian, but other Z80-based games, you just need to reprogram the GAL.

It's so far been tested working with the following games:-

Galaxian (Namco, Midway and bootlegs)
Amidar
Turtles
Pacman (ROM only as the memory addressing is a bit "odd")
Scramble (plus other games on Scramble hardware)

Using a single board does away with the multiple ageing IC sockets that lose their grip over the years, and also reduces power consumption a bit as it uses just one ROM and not the multiple ROMs originally in place.

The final thing is for anyone who does home-brew game coding, or hacking games.  Burning a single ROM is a load easier than having to burn multiple ones.  Also the RAM on the board can be replaced with a Dallas DS1220 NVRAM module (apart from Pacman), so the home-brew coders can write their own high score save routine.

I plan to get this working with more games as time goes on, and also maybe refresh my old Z80 programming skills...

May not have been too clear in my post, I'm not out here to bust this product....it's a great alternative and the price is excellent if installing a battery directly to the PCB isn't your thing

No problem.  Just to add that this module will also survive the fitting of a switching PSU that often creates problems when used with Williams games.

Hi all -

Not wanting to spend £20+ per module importing them from the US, I've designed a PCB for an NVRAM board for Williams Joust, Robotron, Sinistar, Splat, Bubbles, etc. (NOT Defender)

It uses the Dallas DS1220AD nonvolatile RAM (which have had a fair bit of bad press but are great to use, and will also work with the MK48Z02).  It has a jumper to select 2 sets of high scores and settings, and pads to connect the additional data lines for Bubbles which uses 8-bit RAM.  You'll also need a socket for the CPU board, socket for the NVRAM, PCB headers, a resistor, optional capacitor and a jumper.  Takes about 15 minutes to assemble.

I've a load of PCB's left over so selling them for £2.70 per PCB (plus postage from UK).

You can get the Dallas module on ebay for less than £10 so you should have a fully working module for much less than bringing one in from the US.

By removing ROMs, you don't mean removing the 4146 ram on the main board do you?
Do you mean the larger eproms with the windows in them?

What do you think of the way I did the board's connector mod, should be ok?

Yes the EPROMs with the windows on the separate board, they should be labelled with numbers (if not, take the ROM board with the ribbon cable facing up, ROM 12 is top left, just next to the 74154)

Also if you disconnect the interface board and the sound board for now

The connector mod looks just fine

Control panel looks different too.

No "Santa Clara, Ca" under the player 2 control, and a different font for "Player 2"

Some fantastic photos, and some pretty awesome looking games (is that the only "Journey" in Europe?).

Well done for all involved, and hopefully I can get there for next year's event 

Fantastic

He's already done my first holy grail game (Reactor), now he's doing Qix, my 2nd

I wonder what other games will be on the same board...