URGENT: Mod Ms Pacman PCB to run on 64kb EPROMS and not old 2532

[francoisadt1]

Hi CAG'ers

I need some help. My MsPacman PCb do have rom erros.
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/P/Pacman-Mspacman-Troubleshooting-Guide-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)