Nintendo 8 Bit Manual

 
 
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•  Single-screen mirroring points all four logical name tables to the same physical name 
table as shown in figure 3-6. 
 
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Figure 3-6. Single-screen mirroring. 
 
•  Four-screen mirroring uses an additional 2 KB of RAM in the cartridge itself to allow 
logical name tables to each map to separate physical name tables as shown in figure 3-7. 
 
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Figure 3-7. Four-screen mirroring.   
 
3.7 Sprites 
 
Sprites are the characters to draw on the screen. Sprites can be either 8x8 pixels...

 
 
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A common technique used for scrolling involves determining whether sprite 0 is overlapping 
a non-transparent background pixel. If the system is drawing sprite 0, and any non-
transparent pixel in it is in the same position as a non-transparent background pixel, the 
system sets the sprite 0 hit flag in bit 6 of $2002. Therefore if the background tile contains 
only transparent pixels the sprite 0 hit flag will not be set. Figure 19 shows sprite 0 detection. 
The left image shows the background,...

 
 
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two are, of course, mirrors) and figure 3-11 shows the composite image displayed on the 
screen, including sprites. 
 
 
 
Figure 3-10. Horizontal scrolling in Super Mario Bros. 
 
 
 
Figure 3-11. Composite image. 
 
The final image starts on the first name table and stretches across to the second. The 
division between the two name tables is shown on figure 3-10 by the grey line. The two blue 
lines indicate the area which is shown on the screen. To the left of the on-screen portion is 
the...

 
 
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It is clear that the status bar area of the screen is not scrolled in the same way as the rest 
and is fully resident on the first name table. This is typical of status information and is 
handled in Super Mario Bros. by using the sprite 0 hit flag and in Super Mario Bros. 3 by 
generating an IRQ. 
 
The general picture of horizontal and vertical scrolling is shown in figure 3-12. The name 
table shown here as A is specified by bits 0-1 of $2000 and B is the name table after (which 
depends on the...

 
 
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3.9 Television Standards 
 
The NES connects to a television to display the game to user. As a result different versions 
of the system were created for the two television formats, NTSC and PAL. NTSC (National 
Television Standards Committee) is the standard used in North America, most of South 
America and parts of Asia [34]. PAL (Phase Alternating Line) is the standard used in Europe, 
much of Asia, Africa and Australasia [35]. Table 3-1 shows the differences between NTSC 
and PAL versions of...

 
 
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4 - Game Hardware 
 
4.1 Cartridges 
 
NES games came on cartridges known as a Game Pak. The game itself was stored on ROM 
chips inside the cartridge. Some cartridges also featured RAM, powered by a battery, in 
order to allow games to be saved. 
 
 
 
Figure 4-1. Ys cartridge for the Famicom compared to 
Super Mario Bros. / Duck Hunt cartridge for the NES [28]. 
 
Figure 4-1 shows the difference 
between cartridges for the Famicom 
and NES. Nintendo designed a basic 
cartridge for the Famicom,...

 
 
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4.1.1 Memory Mappers 
 
The NES’ limited memory was sufficient for early games, however as they became more 
complex, games became larger and the memory was insufficient. To allow cartridges to 
contain more ROM, the NES had to be able to swap the data in and out of memory when it 
was needed. Since the NES could not address beyond $FFFF, switching hardware in the 
cartridges themselves was used. This hardware was known as a memory mapper or MMC 
(Memory Management Chip). 
 
The basic idea of...

 
 
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The software that can be run using an emulator is usually referred to as a ROM image in 
reference to the original ROM chips used to store it. A simple dump of the contents of the 
cartridge is unlikely to be sufficient as it leaves no way to identify what each part of the file 
means. Two different file formats have emerged to provide this information. 
 
The iNES file format was originally defined by Marat Fayzullin for use in his iNES emulator. 
The format has since been used by most emulators...

 
 
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The iNES format suffers from many problems. It is often misused, with people inserting their 
names in the header, for example. Marat Fayzullin’s involvement in NES development seems 
to have decreased recently and, in the absence of any official updates to the format, many 
developers have specified their own alterations, others have also been devising their own 
mapper numbers. This has led to the format becoming increasingly inaccurate and the 
development of UNIF (Universal NES Interchange...

 
 
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Figure 4-6. Mario Golf disk [41]. 
 
4.3 Game Genie 
 
The Game Genie was a device that allowed 
gamers to cheat by adjusting the way the code 
is executed. The Game Genie was designed 
by Codemasters and distributed by Galoob 
Toys [14]. Other cheat devices worked by 
locking the value of a given memory location. 
For example if the game stores the number of 
lives remaining in location $1000, then locking 
this to 5 would give the gamer an infinite 
number of lives. The Game Genie, however,...