Coming soon to a Pac-Land cab/board near you...

[cmonkey]

Looks like you're in luck! The rom which would need hacking is socketed (SK1-1 at position 6B). The 6Kb of shared work/sprite ram is at the top right of the board (positions 8R, 8P and 8N) and looks to be socketed too. I can't find a schematic for Sky Kid but I'd imagine the hardware layout is identical to Pac-Land so I'd take a very strong guess that the middle one of those 3 is the one that would need replacing with a 2Kb NVRAM module, just like Pac-Land.

According to the Mame Sky Kid driver there are two different versions of Sky Kid which use the CUS63 chip (sub-cpu at position 3B marked 63A1). These are known as skykid and skykido in Mame. I'd need to know the 32-bit CRC value of the rom at position 6B before I started to apply the hacks so that I would be sure I was targeting the correct board that you have. Do you have an eprom reader so you can read the contents of that rom? Other than that it would be trivial to add to high score save to this board

 

[cmonkey]

Ok, a little update on this.

I've now managed to implement software reset of the high scores via holding down the 1-player start button/2-player start button/jump button at boot time or when exiting service mode. This was the best solution I could think of. The chances of you accidentally holding down all 3 buttons simultaneously at power-up or when exiting service mode are slim but don't say I didn't warn you if you accidentally leave a copy of <insert_name_of_favourite_heavy_book_here> on them at boot time and watch as those precious high scores you've worked so hard to achieve over the past few months magically disappear before your very eyes!

There are now only 9 bytes free in rom 1 to implement a decent attract mode. Hmmm. Not easy!

Here's a video of how things look if you boot the machine with the usual SRAM module at position 9N. I assume that the hardware itself sets all values in the ram modules to a value of $f5 at boot time and then ordinarily the boot sequence would go through the entire contents of ram and zero it all out. However, due to the fact that we need to preserve the high scores through the boot sequence I altered the code to skip the zeroing of the bytes in the range $2140-$218f (where the high score table is). This means that using a normal SRAM module it leaves the original values of $f5 in those positions which were set by hardware at boot time. This behaviour isn't repeatable in MAME as it doesn't emulate a machine down to such a low level, it simply allocates a chuck of your computers memory and zeroes it. So this is why the high score table looks strange in this video!

The next video is of the SRAM module at 9N replaced with an NVRAM module containing zeroes throughout all 2048 bytes of the module. This results in the high score table looking strange on first boot as there is no character in the charset rom with a code of $00 so the game simply displays a white block where the characters of the high score names would go. After you've played 5 games and got 5 high scores you'd never see this slight anomaly again.

The final video is of an NVRAM module containing a full set of 5 high scores. This is how I would expect most people's high score tables to look like after a few games. The combo of holding down the 3 buttons at boot time causes the game code to copy the default high score table from rom to ram.

 

[smarty]

Great work on this

Would offer to help test but I only have a Namco board with world rom set.

Looking forward to this big time

 

[cmonkey]

Stay tuned..... I'll have the Namco patches done within the next week. Are your chips at positions 9N and 8D socketed so that you're ready to go?

 

[smarty]

...Are your chips at positions 9N and 8D socketed so that you're ready to go?

I'll drag the cab out tomorrow and check, if they're not already socketed they soon will be

 

[smarty]

Not sure if i've missed the boat to do any testing on this, but i socketed my 9N ram tonight, board still play fine so quite happy to test if required.

Cheers, Mart.

 

[Alpha1]

Awesome awesome thread this. Rated 5 stars from me!

 

[virtvic]

I haven't got the gear to dump roms

 

[Del Griffith]

Excellent work, Look forward to the Namco version

 

[cmonkey]

All 5 versions of Pac-Land are now completely patched and working fine (Bally Midway version tested on an actual board and Namco versions tested in Mame).

I'm just finishing up writing the extensive documentation to go with all the patched roms and then I'll release the lot either later tonight or tomorrow night if I get too tired to finish up tonight!

The documentation is pretty lengthy and most people will have fallen asleep by the time they get halfway through it probably but I prefer to let people know EXACTLY what has changed in the game so that they can learn from it and maybe produce a high score save kit of their own one day.

@smarty - have you got a Dallas DS1220AB 2Kb NVRAM module (or equivalent) to replace your sram module at 9N? You'll need one if not.

Not long to wait now boys.....

 

[trm]

Does the documentation explain how & where you've squeezed in the extra code along with your approach? I've messed about inside games before and I always enjoy reading someone else's perspective, and cool detail on how you jammed it in is well, cool

Excellent work dude!

 

[cmonkey]

The documentation explains EVERYTHING! I hope that at least one person reads it all the way through, it'll make the hours that I spent writing it worthwhile. It will also be interesting to get some feedback on the documentation, as well as the mod itself.

Release will be later tonight.