Warp Warp ROM 8 error still. What am I missing here??

yaryar

Well-known member
Joined
Feb 24, 2011
Messages
363
Reaction score
252
Location
Arabi, Louisiana
Warp Warp ROM 8 error still. What am I missing here??

Been messing with this PCB for too long now and I am completely out of options. Maybe someone here might have some advice. Here is the summary:

Received game, game played fine for a few hours. Turned it on the next day and it showed ROM 8. Here is what has been done so far:
1) Verified all voltages are good.
2) Pulled and verified all EPROMs against ROMIDENT.
3) For the hell of it, burned a new set of EPROMS, same issue
3) Verified activity on Address and Data bus lines, as well as /CS signal on the EPROMs.
4) Combined all 4 ROMs code into a single 128K EPROM, did a small reversible mod to the board to accomodate the 128K EPROM. I also lifted A12 and A13 from the CPU socket and ran bus wires straight from the CPU to the 128K EPROM, same error.
5) Went into the games code and identified where the program goes in the event of a ROM error, and blanked that out, burned that code to a new EPROM. Now the game will go past the self test and into the attract mode, but all that is seen on the screen is 'Player 1 Player2 and Credits'. The game hangs there. If I flip the self test switch on and boot the game up, the self test screen appears normal and you can move the joystick around for the joystick test, and the music test appears to work OK, but flipping the switch back to game mode yield the same frozen screen with Player 1, etc.

I really don't know what else to check at this point. I have a Fluke 9010 but no 8080 pod so I can't go from that angle. One thing I noticed is that the big square 15 watt resistor on the PCB gets red hot to the point where you can smell it, but since the voltages are all good, don't know if this can be related.

Any ideas or advice is very greatly appreciated.
 
I was able to acquire a second Warp Warp PCB, that was rebooting constantly. Found a bad buffer and got the board to come up, ALSO WITH A ROM 8 ERROR!!!! I can't see 2 boards with the exact same problem, so the problem would be external to the board, but looking at the schematics I can't see anything external that could possibly cause this. I checked the AC power coming into the board (as the board converts the AC to DC), and those voltages are all within specs. What is peculiar also is that the manual shows ROM 1,3,5 and 7 errors but doesn't say anything about a ROM 8 error.
 
Last edited:
Sounds like you are familiar with code - so why not step through it in MAME to see what is actually being tested in order to trigger a ROM 8 error?

(Maybe it's the graphics ROM?)
 
Sounds like you are familiar with code - so why not step through it in MAME to see what is actually being tested in order to trigger a ROM 8 error?

(Maybe it's the graphics ROM?)

Yep, I stepped through the code, one line at a time, watching the CPU registers, and a ROM 8 error will be triggered if the checksum of the graphics ROM @4800-4FFF fails. This is a ROM that I never even looked at, and the manual never mentioned it. I was solely focused on the game ROMs!! Since both boards have the same error, I'm hoping that the graphics ROM is bad on both boards, otherwise I'll really be at a loss at this point if this ROM checks good in ROMIDENT.
 
If it's populated with 2716s, it needs 8 roms instead of 4....

...so your problem is probably with the upper half of "ROM 7"...

Both boards have 3 -2732's and one 2716 for the game ROMs, and one 2716 for the graphics ROM.

Going through the ROM test code in the MAME debugger, when it's working its way through the first half (3000-37FF) of the last game EPROM, the ROM value (if an error is encountered) is '7'. It then sets the HL value to 4000(the beginning address of the graphics ROM), and starts computing that checksum value. If an error occurs on that EPROM, it computes the value of '8', thus the ROM 8 error. If I hadn't stepped through the code and watched the 8080 registers, I would have never seen this, and would probably still be looking elsewhere for my problem. One thing of concern is that I have 2 boards with the exact same problem, so what are the odds of the graphics ROMs on both boards being bad???
 
Update:

I pulled the graphics EPROM on both PCBs and of course they both checked good. I burned new ones and made sure that they matched the Game ROMs set.

At this point, according to the error that i'm seeing on the screen, the game ROMs check good and it's failing the graphics rom check. I went back into the game code using MAME debugger and Hex Workshop and edited the code so that it runs the RAM check, but skips over the ROM check. I tested this patch in MAME and the game runs perfectly. HOWEVER, when I burned the patched ROMs and put them into the PCB, the game comes up completely locked up and won't even run the RAM test. What the f%^k!!!!! How can it run fine in MAME, but not at all on the PCB??? Is this damn game possessed???

Unless anyone chimes in with something different, I'm going to disable the on board power supply on the PCB (it generates +5, +12, and -5) and wire a switcher in, even though my voltages look OK. Definitely have nothing to lose. At this point, what else could cause both PCBs to exhibit the exact same problem?
 
So this issue is finally solved. The problem ended up being, on BOTH BOARDS, the hex buffer/inverter at 3C. It appears that the ICs sole purpose in life is to allow data from the graphics ROM to be read by the CPU, for checksum purposes and nothing else. Swapped this IC on the boards, and now the boards are running fine again.

Now as to why bypassing the ROM check in the game code causes the game to freeze up, I have to idea. May investigate that later.
 
Back
Top Bottom