Space Invaders Single Rom hack

DarrenA

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OK, time to ask the masters.
I have been tinkering with a old SI board set. Taito 3 board stack, that I got from fellow KLOV'er. Board was somewhat restrapped for 2716's but looked like they gave up. I finished the rework, installed a fresh set of 2716's and booted the board just fine.

So in a thought I desided to do the 2764 Single rom mod, that has been posted here a few times, I get nothing but (what I call jailbars) and the random splash of garbage on the screen.

These are the same roms I used in the 2716 chips but copy /b togather. then burned to a single chip.

Folowed directions to the letter still nothing. So I plug in the 2716's again, and everything is fine.
I have done a few single rom mods and NEVER had problems like this.
I can take any pictures needed, link to the directions ect...
This is starting to Pi$$ me off. :(
 
http://forums.arcade-museum.com/archive/index.php/t-135965.html

Look at the 9th post down from Orion3311 (Though this is for a L Shaped board)

http://forums.arcade-museum.com/attachment.php?attachmentid=95196&d=1325856010
that is more or less my board.

Here is another link to another SI hack (this is the one I went by.) (3 Board Stack)
http://forums.arcade-museum.com/showthread.php?t=217359

Between those two I should have had it working. I even went as far as testing every AD line to make sure it went to where it was "supposed" to go.
The only strange thing I found was my A10 line went noplace, just dead to a non-connected Via.
I tried to jump that to a pin on one of the 7408's IIRC chip #22 pin 6?? or 3??... Can't remember right off.
Still the same effect.

As for the extra Ad lines, the directions were simple to follow, find RA11 connect pin 23 to that, Find RA12 and connect pin 2 to that. All of those are next to S6 on the board.
 
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OK, I'll step aside as I've only ever worked on Midway SI boards... never touched a Taito.

Only thing I can think of is to make sure your ROMs are concatenated in the proper order. It's not intuitive with the Midway EPROMs; it's reverse of alphabetical order... H, G, F, E. Have no idea about Taito labels, but make sure that you "copy /b file+file+file+file bigfile" with the files in the order they are mapped in memory.
 
Yup thats the order, copy /b invader.h+invader.g+invader.f+invader.e I64.bin
I went to winhex and everything matches where its supposed to be.

I have to take a break tonight and look again tomorrow. maybe I am missing something simple and my frustration is causing me to miss it.
 
I'm just throwing an idea out there, forgive me if it's stupid.

I was under the impression that the roms originaly were 2708 files, but when you burn them into a 2716, it works because the board ignores the top half or bottom half (can't remember which) of the rom.

So if you burned the 4 files, you'd only have the bottom of the 2764 filled up, so maybe you need to double up the original files, and then combine them?

Again I may be completely wrong, just guessing.
 
HMMMM. now thats an Idea.... When I got this board it HAD TMS2716's on it. 4 of them.
Well if thats the case, I better look into the files in winhex and see if theres an empty half of a doubble image there.

The other board I got has 6 TMS2708's on it. so, going off that 2 of the 2716's should be half empty or have doubble image on them.

I will check.
 
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