SNK P.O.W. daughter board missing + rom size

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    • SNK P.O.W. daughter board missing + rom size

      So I got this 5$ board that I tried and the daughter rom board is missing...

      thanks to LukeMorse () I see he gets the exact same results as me when his daughter board is installed "backwards".

      I see other boards without that daughter boards working and I see that ROM1 to ROM4 are filled with 4 x "nec 8831xd" instead of 16x 8k1 (?) on the daughter board (ym2149.com/arcadepcb/pcb/snk/pow_a7008-sub_pcb_partside.jpg)

      I figure I can join 4x4 and get this board working but I can't quite understand which rom I need ...

      Help?

      a working board without the daughter board:


      the NEC chips on the left



      my board with these 4 sockets unpopulated.



      Thanks!
      +++
    • Interesting... looking at the MAME driver: github.com/mamedev/mame/blob/m…rc/mame/drivers/snk68.cpp

      it seems that the version without the daughterboard is not dumped!

      we could probably make it though.

      it looks like that section are the "880" "gfx2" ROMs given the rom sizes on the daughterboard and the fact that those 4 16-bit ROM locations are 40 pin I'd guess that those are either 27c4096 or 27c400, there are two different pinouts there and you'll want to use a multimeter to determine which pinout that location matches.

      For ccombining the ROMs there are 16 8bit/1Mbit ROMs. but they're pairs of 8-bit ROMs being used as 16-Bit ROMs so you'll need to interleave those pairs to make 8 16bit/2Mbit images, and then concatenate every 2 to make the 4 16bit/4Mbit images to burn.

      assuming that the logic/PLDs aren't different between the two versions of the game I see no reason it shouldn't work. Definitely socket those locations though. the most time consuming part will be pulling all the solder out of those IC locations.
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    • twistedsymphony wrote:


      For combining the ROMs there are 16 8bit/1Mbit ROMs. but they're pairs of 8-bit ROMs being used as 16-Bit ROMs so you'll need to interleave those pairs to make 8 16bit/2Mbit images, and then concatenate every 2 to make the 4 16bit/4Mbit images to burn.
      27c4096 I've got so I will try these.

      16 x 8/1
      pairs of 8 used as 16
      Interleave those pairs to make 8 16/2
      concatenate every 2 to make 4 16/4

      :huh: X/ :S <X

      err... could you please say that in english ? :P
      I am understanding that I need to join each 2 roms to create 8 then every 2 to create 4 but the "interleave" part I don't understand how to do?

      Thanks!
      +++
    • Mrhide wrote:

      27c4096 I've got so I will try these.
      don't just "try" them. verify the pinout first given how these two line up you'd probably be safe attempting to use the wrong one, but on some other scenarios that could lead to burning up chips and/or traces.

      just take a multimeter and check if the Vcc and GND pins go to Vcc and GND. altnatively the Address and Data pins should all be routed together between the EPROMs with the OE and CE not routed together.




      Mrhide wrote:

      err... could you please say that in english ?

      so when you have an 8-bit EPROM it has 8 output pins (8 bits of data for a given address).
      when you have a 16-bit EPROM it has 16 output pins (16 bits of data for a given address).

      so when you're using 2 8-bit EPROMs to act like a single 16-bit EPROM you basically enable both chips at the same time, give them the same address, and simply have the 8 output pins of one chip be the lower 8-bits and the 8 output pins of the other chip be the upper 8-bits.

      when trying to "join" that data for use on a single 16-bit chip you have to "interleave" it. meaning you take 1 byte from the lower chip, then one byte from the upper chip, then one byte from the lower chip, then one byte from the upper chip and so on... imagine joining two stacks of paper except you need to alternate pages from each stack when making the new stack.

      There are some hex editors and other ROM tools that will perform this for you. Alternatively MAME interleaves the data when it's loaded into memory so you could also load the game in MAME debugger and dump out that memory region.
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      The post was edited 1 time, last by twistedsymphony ().