10
STAR*TECH JOURNAL/DECEMBER 1982
A Regular Monthly Feature Technically Outlining a Newly Released Game
GOTTLIEB'S "Q*BERT"
By Joe Connor, Active Amusement Co., Philadelphia, PA
Gottlieb's latest video, "Q•BERT", is the second
game (the first was "Reactor") employing the Graphics
G enerator 2 video system. This system has been
totally developed and designed by Gottlieb's video
engineering department in Bensenville, Illinois. It
includes features from Gottlieb's pinball games as
well as other new designs based on Gottlieb's analysis
of other major manufacturers' video games and those
particular areas which provide for greatest reliability
and servicing. The only basis of comparison from a
service viewpoint would be "Reactor'' and that is
difficult what with the limited number of those in
operation.
Game play starts with the player controlled
Q•BERT character appearing at the top of a 3-
dimensional pyramid of cubes. The joystick will move
Q•BERT from cube to cube by hopping in any of four
diagonal directions. When all the cubes in the pyramid
have been changed to the designated color, the screen
will advance to the next round. The Q•BERT char-
acter can move anywhere ( except jumping off the ~ide
of the pyramid) to avoid an array of characters which
pursue him and block his path. There are four rounds
for each of 9 different skill levels. Bonus points are
awarded at the end of each successfully completed
round. A very detailed description of game play, round
progressions and scoring can be found in the production
game manual (pages 4 and 5).
SYSTEM POWER
The system power distribution (see Figure 1) is very
basic and should pose no problems. The major
components are a transformer assembly located in the bottom of the machine,
and a power supply mounted on the back door next to the logic board.
TRANSFORMER ASSEMBLY - The transformer has 5 secondary windings
which provide all necessary AC voltages. This assembly is not unlike the one
Atari uses in that, in addition to the transformer itself there is also a bridge
rectifier (EL-42) and large filter cap ( C 1-50,000 MFD 25V) mounted directly
on the assembly. This high current unregulated DC voltage acts primarily as the
input to the + 5 volt regulator on the power supply. Obviously, any failure of the
filter cap or bridge rectifier would be reflected in the +5 volt supply.
Unlike Atari, there is a second bridge rectifier (EC-42) which provides
approximately 4.5vdc to power the coin door lamps. There are 5 fuses mounted
on the transformer to protect the primary as well as secondary windings.
POWER SUPPLY - The power supply is a new, more simplified, (and
hopefully more reliable) version of the pinball power supply. It actually is a
combination of both the game and sound/speech power supplies used in all
recent Gottlieb pinballs. The +5 volt regulator circuit employes a program-
mable zener diode (TL431) and TIP 31B transistor to control the gain of a
2N5879 pass transistor (Ql 1). It provides regulated +5 volts at 6 amps and is
adjustable by means of a 100 ohm trim pot (VRl) mounted directly on the power
supply. Protection from an over-voltage condition is provided by the SCR-
controlled "crowbar'' circuit which will trigger at 5.6 volts.
There are 4 other voltages provided by the power supply. These include:
+20 - Full wave rectified, unregulated, unfiltered, non-adjustable
+30 - Regulated (zener diode (IN5363) controlling the base of an emitter-
follower pass transistor (2N3055), non-adjustable
+12- Regulated (packaged IC regulator) non-adjustable
-12 - Regulated (packaged IC regulator) non-adjustable
There are no test points marked on the power supply, but there are voltage-
present indicator LEDs for the +5 , + 12, +30, and -12 volts. Interestingly,
these LEDs are located at the DC inputs of each of their respective regulator
circuits. There are also separate connectors for the input AC voltages and
output DC voltages. This can be especially helpful when trying to determine if a
voltage is being held down by something external or the power supply is failing
under load conditions.
Voltage
Source
Destination
+11.5
Trans. Assy.
Power supply, Logic
board
+ 5
Power Supply
Logic, Sound/speech
board
Sound/speech board
+12
Power Supply
-12
Power Supply
Sound/speech board
+20
Power Supply
Coin counter
+30
Power Supply
Sound/speech board,
knocker coil
POWER SUPPLY HARDWARE
2N5879
5vdc pass transistor
2N3055
+ 30vdc pass transistor
TL431
+5vdc programmable zener
7812
+ 12 regulator
7912
- 12 regulator
The power section should be quite reliable and is
well protected by a total of I I fuses. These fuses
should protect against almost any short which could
develop on any of the AC or DC lines.
BOARD SET
LOGIC BOARD - A single main logic board (mounted on the back door) is
used in "Q•BERT". This large (19" x 14") board can be broken down into two
main sections: the CPU and video generator. The CPU section consists of an
Intel 8088 microprocessor (see Figure 2), 24K of program memory, and 5 input
and output ports. The video generator is semi-independent (separate clock
machine) and contains both the foreground and background generator circuits.
This display section, like that of most recent video games, is by far the principal
(most ICs) section of the board. By working semi-independently, it affords the
processor more space for program memory and the time to execute it. The
graphics needed (they must be spectacular to sell a game) require "this state of
the art" design. This board is almost identical (battery RAM added and larger
EPROMs) to the one in "Reactor'' - the first game using the GG2 board
system.
BOARD HARDWARE
Microprocessor
8088*
Program PROMs
2764 (3)
Foreground object PROMs
2764 (4)
Battery RAMs
6116LP-4(2)
Line buffer RAMs
93422 (2)
Background character PRO Ms
2732 (2)
Background buffer RAM
4118
*The Intel 8088 is a new generation high performance HMOS microprocessor.
It possesses attributes of both 8 and 16-bit microprocessors and has direct
addressing capability up to 1 MByte of memory (Gottlieb only uses 64K, the
upper 4 addresses are not used). This processor also has direct software
compatibility with the 8086 (the 16-bit microprocessor used in " Caveman").
The data bus is multiplexed on the lower 8 address lines (ADO-AD7). This
"time multiplexing" provides the most efficient use of pins on a standard 40-pin
package. The designer has the option of either a "minimum" or "maximum"
mode (see Figure 2- IC pinouts). Being of single processor design, "Q•BERT"
employs the minimum mode (pin 33 tied to +5 volts). This processor has
numerous capabilities, many of which aren't even used in " Q•BERT" , but may
be found in future games using this system (GG2).