Mod Ms Pacman PCB to run on 64kb EPROMS and not old 2532 to play a Perfect pacman

  1. Mod Ms Pacman PCB to run on 64kb EPROMS and not old 2532 to play a Perfect pacman

    12-01-2020, 11:15 AM
    Hi CAG'ers

    I need some help. My MsPacman PCb do have rom erros.

    My aim is to play a perfect pacman this year and get a good run on mspacman in upper range between 700K and killscreen this year - all normal speed. First I wnat to fix mspacman PCb just to run normally then change it to switch to pacman.

    My ROM 6F is faulty and also maybe 5E and 5F.

    To replace I have asked my brother in USA to buy the ROMS and will brought it to South Africa
    but he will only be in SA next year.

    I have bought a small EPROM programmer (only one in SA) that can write AT28C64 (64kb).

    To replace the 6F with 2764 kind of EPROm I need to map the correct pins.

    Original: PCB Mod paage:
    http://www.pinrepair.com/video/pacman.htm

    The above mentioned page do explain to map 512kb EPROM with multi rom in one EPROM.

    The problem is which pin A12 need to map if I do use a 64kb type chip and not a 512kb.

    The 512kb chip do have much more pins

    GOTO to section: "Converting a PacMan board to Ms.Pacman using two EPROM's, and Two Game Pacman Hack."
    http://www.pinrepair.com/video/pacman.htm

    To start :
    A) I only want to replace 6F with 64kb EPROM 28pin and just map to correct pins using the "principles" of the above but not a multi EPROM with a switch as the multi pac mod. Just plain copy of 6F into At28C64(2764).
    B) Then thereafter do replace 5E & 5F with a 2764 type EPROM
    C) Then if all is working then play around with put in a switch between mspacman vs pacman 5e/5f row by
    filling in 5E and 5F of mspac in lower bank of first 32kb of ram and pacman 5E & 5F in upper 32kb bank of ram.


    I probably copy 6F (normal speed) multiple times to fill lower and higher ram area. Once working then to split to have the first
    32kb filled with 8 times 4kB of 6F Normal speed and upper 32kB fast speed of 6F.

    Why I am cautious is in this manual page 35, it describe that EPROM banks are in tri-state mode.
    So that is why it is connected to 7N. Purpose of 7N described in:
    https://klov.com/manuals-videogames/...uide-Part2.pdf
    (Page 35)



    QUESTION 1:
    Now the problem I face is in the example of 512kb the chip do have A13,A14,A15 extra. So where must A12 go for 64kb chip becuase that is the highest A-pin that can be selected to initiate the higher bank of RAM. So below A14 is connected to 7N but if I do use a 2764 type EPROM I do not have a A14 at all. So does my A12 connect then to 7N? What must connect to 6B? Why I need connection to 6B?


    QUESTION 2:
    Also where is :
    6B pin 5 (test connector 8th "finger" from the bottom component side)
    What is meant by "8th finger" and "bottom component"?


    QUESTION 3:
    How do I setup switch on EPROM 64kb for switch between mspacman 5-row roms in first 32kb bank to pacman 5-row roms in second bank of higher 32kb in the 64kb chip?
    Is it put a switch on the A12 line? So A12 selected the chip is set "high" then upper region will be read, otherwise lower bank will be read?


    6 ROM Set 512KB Setup:

    =====================
    2) Add a 28 pin socket into 6J with pins 1, 2, 27, & 28 exposed. Also bend pins 20, 22, 23 & 26 out horizontally (so you can solder wires to them) and press the socket firmly into the PCB socket at 6J.
    3) Tie pins 20 (CE\) and 22 (OE\) to 7N pin 12.
    4) Tie pin 23 (A11) to 7L pin 9.
    5) Tie pin 26 (A13) to 7N pin 14.
    6) Tie pin 27 (A14) to 6B pin 5 (test connector 8th "finger" from the bottom component side).
    7) Tie pin 28 (Vcc) to +5 volts.
    Tie pin 2 (A12) to 7N pin 15.


    5 ROM Set Setup:
    To use a single EPROM for Row 5:
    ===================================
    1) Add a 28 pin socket into 5F with pins 1, 2, 27 & 28 exposed. Also bend pins 20, 22, 23, & 26 out.
    2) Tie pins 1 (Vpp), 27 (PGM\) and 28 (Vcc) to +5.
    3) Tie pin 20 (CE\) and 22 (OE\) to GND.
    4) Tie pin 23 (A11) to 4F pin 1.
    5) Tie pin 2 (A12) to 5L pin 5. If you are running just Pacman or Ms.Pac (and hence a 2764 for Row 5), stop here.


    EPROM BANK SWITCH BACKGROUND from Arcade Cabinets:
    http://www.arcade-cabinets.com/resources.shtml
    \Quote:
    " Anyways, with "banking" you'll put the code for different games in different sections of a large EPROM, where each section serves as a bank of memory. To select the different banks of larger EPROMs, you'll run a wire to a switch that hardcodes the EPROM's upper address lines to particular values that point to the section of the EPROM corresponding to a given game, and if you have spare positions on the switch you can handle any control panel discrepancies with the switch. Unfortunately, any differences in peripheral boards (like sound boards), memory size, or interrupts are going to be more difficult to handle, since these are differences in the motherboard architecture will hinder the sharability of the motherboard between various game's code.

    If you have extra poles on your switch, you can select the use of different hardware or modify things like interrupt handling. If the total length size of the games' code differs, you can avoid have addressing problems, in cases where the sizes of the game code are multiples of a power of two -- place multiple copies of the smaller game's code until you fill a bank equal to the size of the larger game's code. This way, the contents of the upper address lines won't be noticed when the smaller game is playing. The idea behind these types of conversions is that "cheap hacks" are the order of the day. Silicon is cheap these days, but wire is still a pain to wrap, so don't be shy about using lots of EPROM space if it'll simplify the design... ".

    Regards
    Francois du Toit (francoisadt)
    Last edited by francoisadt; 12-01-2020 at 08:08 PM.
  2. 12-04-2020, 12:03 PM
    My first idea was to built an adaptor and not to hack at all but I was not sure where what wire goes and therefore I opted to seek any information that do
    show where the wires would go.

    See my attached Excel attempt. It is based upon reading on potential adaptors for Commodore 64 ROMS.
    ADAPTOR 1 From Internet somewhere
    THis one connect pin 2 (A12) of 28pinROM to pin 21 of 24pin socket (VPP)

    https://forums.arcade-museum.com/att...64-png.480573/



    ADAPTOR 2 from a German Website:
    This one do not connect A12 but connect pin 20 to GND

    https://forums.arcade-museum.com/att...18-png.480574/


    ADAPTOR 3 Wire connection:


    My own derivative based upon above and below "Pacman PCB modification Hack"
    https://forums.arcade-museum.com/att...94-png.480577/



    ADAPTOR METHOD QUESTION 1:
    So is the answer a mix between ADAPTOR 1 and 2 I got listed as ADAPTOR 3 above? or which adapter is correct, if not any of them how much pins of a 2764 (AT28c64 map to a 2532).
    Layout of of pins in attached .PDF
    Attached Images Attached Images  
    Attached Images Attached Images
    Last edited by francoisadt; 12-04-2020 at 12:05 PM.
  3. 12-04-2020, 01:42 PM
    I'm sorry I haven't looked at the datasheets for these respective EPROMs to fully illuminate what you've already written, but I hope you'll allow me to ask a couple of questions to cut right to it.

    Q1) You're trying to replace an 8 kilobyte (64 kilobit) EPROM with a 64 kilobyte (512 kilobit)?

    Assuming the answer here is "Yes:"

    Q2) You want to know what to do with the 3 extra address lines (A13-A15) on the larger EPROM?

    Q3) Are there equivalent pins on the larger EPROM for any of the connected pins on the smaller EPROM, other than A13-A15?
  4. 12-04-2020, 08:43 PM
    Quote Originally Posted by grinder2112 View Post
    Q1) You're trying to replace an 8 kilobyte (64 kilobit) EPROM with a 64 kilobyte (512 kilobit)?
    Francoisadt: No, the otherway around. The example that I did find uses a 512kb to install a multi-pac setup but I only want to fix a straight setup using a 64kb ROM becuase that is all I can find/bought here in South Africa. All gamers in USA & UK are fortunate having suppliers of components, here we have none, also none expertize, all those guys are either "dead/passed away" or not in the trade and non-traceable/contactable.

    So in a normal setup the ROM image of each of the pacman ROMS are actually 4kb written in a 32kb ROM of type 2532. So a 24pin socket with a 24pin ROM layout.

    Now I do not have 2532 ROM, neither a EPROM programmer able to write a 2532 EPROM.

    I can only write 64kb (28pin EPROM).

    In the normal setup the ROM image will take up the first 4kb of the 32kb (2532), leaving the higher bits unwritten/unused

    Now here the woraround setup the 4kb image will also take up the first 4kb of the 32kb (2532), leaving the higher bits unwritten/unused.

    Both is like original ROM because the checksum is 100% the same. Noawadays all the Pacman ROMS bought from places like hobbyroms are just refurbished 2532's , cleaned, write out the 4kb ROM images (as from MAME) into a 2532 with the correct
    checksum. So I just do the same, Only difference here I do have a 64kb EPROM, more pins at the top.

    One can write out the 4kb ROM image 6 times in the 2532 and 16 times in 64kb to fill up all the space.

    In Normal operation only the first 4kb of a ROM image is read (lower bank) not any of the higher halves.
    To read higher halves that is where the 512kb hack comes into play to "select/choose" the higher bank to be read.


    Quote Originally Posted by grinder2112 View Post
    Q2) You want to know what to do with the 3 extra address lines (A13-A15) on the larger EPROM?
    No otherway around, the example clearly show larger 512Kb EPROM but I am using a smaller 64kb ROM

    As you see in the adaptor, show the 28pin EPROM to fit into a original 24pin socket.

    Quote Originally Posted by grinder2112 View Post
    Q3) Are there equivalent pins on the larger EPROM for any of the connected pins on the smaller EPROM, other than A13-A15?
    Yes, you see, all the equivalent pins I have mapped in the adaptor pictures.

    The extra pins on a 28pin EPROM vs 24pin EPROM are:
    pin 1,2,27,28

    Only the A12 (pin 2) on 64kb EPROM is extra I do not know where to redirect.

    I am also unsure of what to do with pin A11 on 28pin although the "512" mod method so show A11 redirect to 7N or 7: but in the
    original 24pin socket there is an A11.

    Also pin 21 VPP on 24pin socket I am unsure off.
    streaming mspacman normal and turbo speed at: https://www.twitch.tv/francoisadt

    Francois du Toit
  5. 12-04-2020, 09:22 PM
    Quote Originally Posted by francoisadt View Post
    ... The example that I did find uses a 512kb to install a multi-pac setup but I only want to fix a straight setup using a 64kb ROM...

    "The example" you refer to a couple of times in your description: Is that currently the setup on your PCB? What EPROM is currently in place on *your* PCB?
  6. 12-04-2020, 10:26 PM
    Quote Originally Posted by grinder2112 View Post
    "The example" you refer to a couple of times in your description: Is that currently the setup on your PCB? What EPROM is currently in place on *your* PCB?
    I actually do have two normal original Ms. Pac-Man PCBs with daughter board bought from MikesArcade (USA) two years ago.
    All roms in my boards are original 2532 in original 24pin sockets in correct positions.

    Both of them 6F are defunct (scrambled screen and resets all the time). So maybe other ROMS are also not working as well,
    one screen test according "pacmanrepair" and MikesArcade page point to 5E or 5F also not working.

    To start with I just want to replace the ROMS like for like step by step but using 2764s (AT28C84 to be exact).

    Once I do have a 6F -normal speed working and connected using a 28pin then only I be moving to IF 5E or 5F is still not working.

    So I be testing out both Ms. Pac PCBs see which one work first.
  7. 12-04-2020, 11:32 PM
    Hi Grinder

    I do not want to cross post but here is more detail on the adapters I have come across.

    Posted on KLOV forum:
    https://forums.arcade-museum.com/thr.../#post-4253216
    streaming mspacman normal and turbo speed at: https://www.twitch.tv/francoisadt

    Francois du Toit
  8. 12-05-2020, 06:26 AM
    Hi Grinder

    To correct my post below. I was wrong the EPROMs are not 64kb each but 64kbits which equal to 8kb each.

    Each mspacman ROM is 4kb space.

    The EPROMs probably be as follows using 2764?

    EPROM ONE:

    64kbits equal 8kb (6E & 6F Mspacman)
    ====================================
    pacman.6e
    pacman.6f (normal speed)

    EPROM TWO:

    64kbits equal 8kb (6H & 6J Mspacman)
    ====================================
    pacman.6h
    pacman.6j

    EPROM THREE:

    64kbits equal 8kb (5E, 5F Mspacman)
    ====================================
    mspacman.5e
    mspacman.5f

    EPROM FOUR:

    64kbits equal 8kb (5E, 5F Pacman)
    ====================================
    pacman.5e
    pacman.5f
    streaming mspacman normal and turbo speed at: https://www.twitch.tv/francoisadt

    Francois du Toit
  9. 12-05-2020, 07:25 AM
    I've been trying to simplify the conversation by asking a single, straight-forward question at a time. Your data dumps undoubtedly contain useful information, but its not progressing my understanding. So, let's take this a step at a time.

    My current understanding:

    1) You have multiple PCBs that you suspect have corrupted ROMs.

    2) Those PCBs have their original ROMs, which are using 8KB (64kb) EPROMs.

    3) None of the PCBs have been reworked to enable some sort of multi-ROM selection.

    Is this correct? If not, concisely give me the correct information.

    I think I might have some good advice, but I need to understand your situation first, so I don't end up dispensing *bad* advice.
  10. 12-05-2020, 07:30 AM
    Just a little bit about unit abbreviations:

    Kb = kilobit = 1000 bits
    KB = kilobyte = 1000 bytes

    Kib = kibobit = 1024 bits
    KiB = kibobyte = 1024 bytes

    Kb is sometimes used for Kib in situations where it's clear we're talking about memory of some sort, as those capacities are almost always some power of 2. (1024 = 2^10) The same goes for KB and KiB.
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