Irem m81/m72 custom chips

[hezkezl]

I am trying to fix an Irem m81 Dragon Breed board for someone, and have come to the conclusion that one of the customs is bad. When researching, and looking for replacement parts, I noticed that on some boardsets the customs have the IC part number scratched off.

This doesn't make much sense if the chips are actual customs (the PCB has the nanao chip part# listed on the board), but it made me think that perhaps these chips are just rebranded stock chips.

Does anyone have an Irem m81 or m72 game that has the part numbers scratched off of the chips (Hammerin harry seems to be a common boardset with unmarked chips like this)? If so, is there any hint of what the part numbers on them might have been?

Thanks for any help anyone might be able to give. The chip I am interested in specifically is the custom ending in 010.

[system11]

M81 is M72 with a modified layout, schematics exist for R-Type - therefore with photos of a M72 board you can make a good guess for the corresponding chip and find it on the schematics.

[hezkezl]

I have the Rtype Schematics, I'm just trying to figure out what the custom actually is. It's labelled as KNA71H010 both on the board, schematics, and on the chip itself.

Some of the M72 boards, though, have the part number on the chips sanded off. That made me think, why would they go to the trouble of doing that if they didn't want to hide the part number? (For example, this hammerin harry board: http://gamesdbase.com/Media/SYSTEM/Arca ... -_Irem.jpg)

I am guessing that although most of these customs were rebranded, and printed with the nanao part number - due to a part shortage or supply problem they had to order stock ICs that had the original manufacturers part number on it. I am trying to track down that part, because if it happens to be a popular microcontroller or something, we could potentially read the ROM data out of it and fix dead Irem boards without sacrificing others.

The form factor of the 64 pin SDIP looks like a Yamaha or Hitachi chip, (no notch on the top of the chip, and a dot molded into the plastic next to pin 1.)

There are two KNA71H010 chips on these boardsets KNA71H010 (14) and KNA71H010 (15). Both of these chips have different functions for their pins, which leads me to believe they are some sort of microcontroller with onboard rom, and the difference between the two is what is written into the rom.

(15) Takes 8 bits from each of the four sprite roms (each rom holds a bitplane for the sprite - with each sprite pixel being a 4 bit index into a color lookup table.) and interleaves the values, outputting four 4 bit color indices that are then written to SRAM. Other than a clock, and a couple of signals that count the horizontal and vertical lines of the display, not much else is sent to the IC (aside from three unknown lines from another custom)

(14) takes some clock signals, some sram enable lines, and 10 bits of data, and outputs four 8 bit words of data. I think this chip handles the background tiles.

The hunch that the "customs" are actually stock chips is all I'm going on right now. It just seems odd to me that some boards would have part numbers sanded off. Sometimes this sanding can be really sloppy, though, and the part numbers can be seen if the chip is cleaned or dampened with alcohol. I was just hoping someone had a boardset with sanded chips, that might give some insignt into what these chips actually are.

I've been going through datasheets of 64 pin sdip ICs from Hitachi and Yamaha, but have yet to find one that has a pinout that matches these.

[system11]

Some of the M72 boards, though, have the part number on the chips sanded off. That made me think, why would they go to the trouble of doing that if they didn't want to hide the part number? (For example, this hammerin harry board: http://gamesdbase.com/Media/SYSTEM/Arca ... -_Irem.jpg)

Chip scraping is always done to put off bootleggers, and it's often inconsistent. M72 was bootlegged, it could be a reaction to that hence the change in tactic on later boards.

I know someone who might know much more about these technically - I'll ask.