How to run Gauntlet and Gauntlet
II on the same board
following text was written by Jay 'Whip' Grizzard, with support from Eric
Crabill and edited by me.
like most folks who like Gauntlet, you like both Gauntlet I and Gauntlet
II -- admit it, they've both got their good points and bad points. Also,
if you're like most people, you don't have two Gauntlet cabinets lying around
(I used to!--Eric) in your dorm/apartment/house or whatever. And finally,
if you're like most people, you probably don't want to have to do an entire
board swap (or ROM swap) just to switch between the two.
now there is (still) a way to play both Gauntlet and Gauntlet II using the
same board, with a single switch-flip toggling between the two. This also
works to play Gauntlet 2 Player and Gauntlet II except you need two more
27512 EPROMS for sockets 9A & 9B
This hack is NOT intended to allow for easy pirating of Gauntlet or Gauntlet
II software -- please don't use it as such. Also, we take NO responsibility
for any damage you do to your Gauntlet board (or anything else) while attempting
this hack. Though the chances of actually damaging something are fairly small,
they are there, so make sure you know what you're doing before you start
Gauntlet I and Gauntlet II use absolutely identical hardware. The only
differences are some of the ROMs used, and the slapstic copy protection chip.
If the ROMs were replaced with double-sized ROMs, with the highest address
line wired to a switch, flipping that line between 5v and GND would, essentially,
give two completely different ROM images. Other than the copy protection,
this gives two completely functional games on one board.
assume a few things in this documentation. First off, we'll assume that you're
at least semi-technically competent. Second, we'll assume you have Gauntlet
I and Gauntlet II ROM images. Third, we'll assume you have access to an EPROM
get your parts together. You will need:
4 27256 EPROMs (300ns or better)
7 27512 EPROMs (300ns or better)
1 2816 EEPPROM
Various machined sockets (2 to 3 for each chip)
Lots of wire (awg 30 is good)
If you don't start with Gauntlet II you will need
1: Get your ROMs ready.
thing you want to do is get your ROMs ready. Some of the ROMs, we won't be
changing -- in particular, the ROMs in locations 9A & B, 6A & B,
1B, 2B, 1C, 2C, 1L, 2L, 1M/N, and 2M/N will remain the same as they were
in Gauntlet II, so don't do anything with those. (We're keeping 9A &
B, 1B, 2B, 1M/N, and 2M/N because they're the same in Gauntlet and Gauntlet
II. We're keeping the rest because they're ONLY in Gauntlet II, and Gauntlet
doesn't mind them being around). If you are starting from a Gauntlet board
(not Gauntlet II) then you will need to add the appropriate Gauntlet II 6A,
6B, 1C, 2C, 1P, and 2P ROMs.
we will be replacing are those in 13A/B, 10 A & B, 7 A & B, 1A, 2A,
1L, 2L, 6P, 16 R & S. The new images for all of these (other than 13A/B,
which is the EEPROM that stores scores and settings) can be created fairly
simply. The EEPROM doesn't need to be initialized.
the chips other than 10A, simply read in your original Gauntlet I and II
ROMs, and burn new ones, into double sized chips, with the Gauntlet I ROM
on the low half and the Gauntlet II ROM on the top half. For 16kbyte images
(27128), the double-sized ROM to burn is the 27256, and for 32kbyte images,
the double-sized ROM to burn is the 27512. If you are working with files,
an easy way to merge two ROM images is to use the MS-DOS copy command, like
/b some_gaunt1.rom + matching_gaunt2.rom new_merged.rom
10A ROMs download the two files at the end of this page. Burn the G1 file
low, the G2 file high
2: Install the ROMs.
you have your images, you need to wire up a way to switch the high address
line on these chips between 5v and GND. You may choose your own method (it
could be as simple as simply bending up a pin on the EPROMs and soldering
wires or using a single IC socket pin, like I did), but here's what we personally
recommend: Build a stack of 3 (or 2) sockets -- use -MACHINED- (not leaf)
sockets. On the bottom two of the stack, remove the socket pin corresponding
to the chip pin for the highest address line on that chip. On the topmost
socket, solder (or wrap) a wire, and daisy-chain that wire from socket to
socket, in essence shorting the high address lines of all the special EPROMs
used wire-wrapping, building the sockets one at a time, working from the
sound ROMs (up in the corner with the power connector) down around to the
left, finishing with the ROM in the middle. Order doesn't matter, really.
In retrospect, I probably would have started with the ROMs at 10A, then worked
around to the alpha ROM (in the middle) and finished with the sound ROMs.
want to check your sockets with a meter before you install them -- Obviously,
the high address pin from each chip should be connected to the wired up pin
on all the other sockets, and NO OTHER PINS.
pins? Well, on 27256's, the high address line (A14) is on pin 27. On 27512's,
the high address line (A15) is on pin 1. On the 2816, you actually want to
connect to pin 22. [For the un-initiated, IC pins are numbered, starting
at 1, counter-clockwise from the notch on the chip.]
reference, the 2816 is in location 13A/B, the 512's are in locations 16S,
7A & B, 1A, 2A, 1L and 2L. The 256's are in locations 16R, 10A &
B, and 6P.
that's done, you'll have an almost-functional machine. Remember how we mentioned
copy protection above? Well, the copy protection for both games is -different-,
so we've had to work around it by altering parts of the ROMs. However, this
work around also requires just a touch of hardware support -- you need to
replace your slapstic, the chip in location 10C. Grab a 20-pin machined socket,
and solder a wire between pins 4 and 10, then between pins 5 and 9, and plug
this into where the slapstic used to be.
if all is well, you'll have a switcharoo game. If the high address lines
are grounded, you'll get Gauntlet, if they're at 5v, you'll get Gauntlet
II. I, you could used those quick-plug style female connectors, plugged into
the two test points (5v and GND) up next to where the player joysticks plug
in (Note: some boards don't have a +5 test point). I used I single pole double
throw switch (3 wires) as shown on the schematic, It's OK to flip the switch
with the power on. It will crash the program and causes a wacthdog timer
Be sure to check out the Gauntlet Pause Switch page, too. Good Luck.
I own a set of both Gauntlet and Gauntlet II
ROMs, so I need slapstic.zip
of Game select switch (and other circuits)
Only the "Dual Game Select" section is needed for this mod. Even the LEDs
and resistors are optional. See my other pages for information on the other