NES Hardware Myths Examined

[Great Hierophant]

Over the years, I have encountered a variety of misinformation or half-truths about the capabilities of the Nintendo Entertainment System.

I have brought together some of my favorites to consider:

 

Myth 1. The NES's resolution is 256x224

Facts: All NESs output 240 lines. NTSC CRT type TVs, which NESs were designed to use, can only show 262.5 lines each frame, and some of those are used for VBlanking purposes. The casing that holds the glass tube cuts off some lines from the top and bottom, as does the fact that the glass tube is not a perfect square. Programmers realized this, and used the time normally spent drawing these lines for other things as people could not see them. NTSC NESs display those lines, and even in normal CRTs some evidence of this is visible. PAL NESs do output all 240 lines in a letterbox arrangement because the PAL tube can display 312.5 lines, so the image displayed is smaller than the tube. PAL gamers can probably notice the artifacts left by programmers not properly refreshing the top and bottom 8 lines.

 

Myth 2. The NES can display 16 colors on screen

Facts: The NES can output 25 colors on screen at the same time without using visual tricks. Each 8x8 graphic tile, whether background or sprite, can choose from 4 colors (2 bitplanes deep). Background tiles choose from one of 4 sets of 4 colors, sprites from a separate 4 sets of 4 colors. Each set of colors has one color entry devoted to transparency, so each background tile can choose from 12 colors, each sprite tile from another 12 colors. Finally, the background color for the screen is chosen independently.

 

Myth 3. The NES can select its colors from a 52 color palette

The NES selects its colors from a 64 color palette. 52 is not a proper binary limit. There are 16 luminances and 4 levels of brightness. However, the ends of the color scale are dominated by whites and blacks that are indistinguishable. 52 colors is a good estimate of the number of distinguishable colors on an NTSC monitor, but the number may be a bit higher or lower depending on the color calibration.

 

Myth 4. The NES has 2KB of CPU RAM available

The NES's console does have only 2KB of RAM for the CPU's use, and an eighth of that is used for the stack, but zero page is totally free for the programmer. However, the NES can also utilize 8KB of RAM on a cartridge as Save RAM or extra Work RAM or both. Several Nintendo carts like The Legend of Zelda do the former, Metroid does the latter.

 

Myth5. The NES has 2KB of PPU RAM available

The NES's PPU has access to 2KB of internal Video RAM, but can also access an additional 8KB of Character ROM or Character RAM. Many memory mappers only allow the bankswitching of Program ROM, so those cartridges use Character RAM. Advanced MMC5 cartridges use extra 8KB RAM to break one of the NES's graphic limitations, that of each 32x32 background tile block having to share a color palette. A few MMC3 cartridges replace the 2KB of PPU RAM with 4KB of PPU RAM to store four background tile sets instead of the normal two.

 

Myth 6. The NES has analog sound

There is very little, if anything at all, analog about the NES's sound. A pulse wave is simply a variably clocked flip flop, a triangle wave has a linear counter applied to it, and white noise a random number generator. The PCM channel handles 7-bit samples or uses a DMC method to process digitized sounds.

 

Myth 7. The NES cannot utilize sound chips in Famicom carts

The NES's can utilize any sound chip in a Famicom cart by connecting the proper pins to the CPU.

 

Myth 8. The NES cannot utilize Famicom peripherals

The front loading NES can work with just about any Famicom peripheral through the expansion port on the bottom of the NES. An adapter must be created. For the top loader with no expansion port, good luck.

 

Myth 9. The NES cannot work with the Famicom Disk System

You will need to use a Famicom to NES adapter and remove the cover of the front loading NES, but it will work. It will sitck up like an L.

 

Myth 10. R.O.B. is necessary to play Gyromite and Stack-Up

ROB is not necessary to play Gyromite, controller two is. Without ROB, the game is rather easy to beat. He is necessary to get anything out of Stack-Up.

 

Myth 11. The NES can output RGB

The NES's PPU is an NTSC or a PAL part only. It cannot output RGB at all. You need to physically replace the NES's PPU with a Playchoice's PPU and rewire the outputs for it to work. Even then the colors will not be 100% true to the NTSC or PAL NES.

[Jasoco]

Myth 1.  The NES's resolution is 256x224

I could have told you this one. Just measure the pixels in an Emulator.

 

I'm curious, though. How much is shown on an LCD TV or one that has a flat screen where you can almost count the pixels? Can you see any of the VBlanking and such?

 

Myth 10. R.O.B. is necessary to play Gyromite and Stack-Up

Again, another obvious one.

[DracIsBack]

Myth 3. The NES can select its colors from a 52 color palette  

The NES selects its colors from a 64 color palette. 52 is not a proper binary limit. There are 16 luminances and 4 levels of brightness. However, the ends of the color scale are dominated by whites and blacks that are indistinguishable. 52 colors is a good estimate of the number of distinguishable colors on an NTSC monitor, but the number may be a bit higher or lower depending on the color calibration

 

You can thank Nintendo themselves for this. It was marked this way right on a lot of NES boxes and marketing material.

 

Note: Sega is also guilty: The SMS has a 256 colour palette, but the original SMS box said the SMS only had 64 colors.

 

Heck, while we're at it, I remember an Atari customer service rep telling me that the 7800 only had 32 colors, when it also has a 256 color palette.

 

What this illustrates for me is marketing folks trying to break down technical stuff into "easy to understand" competitive advantages, without really understanding the technology.

[Happy_Dude]

Myth 1.  The NES's resolution is 256x224

Facts: All NESs output 240 lines.  NTSC CRT type TVs, which NESs were designed to use, can only show 262.5 lines each frame, and some of those are used for VBlanking purposes.  The casing that holds the glass tube cuts off some lines from the top and bottom, as does the fact that the glass tube is not a perfect square.  Programmers realized this, and used the time normally spent drawing these lines for other things as people could not see them.  NTSC NESs display those lines, and even in normal CRTs some evidence of this is visible.  PAL NESs do output all 240 lines in a letterbox arrangement because the PAL tube can display 312.5 lines, so the image displayed is smaller than the tube.  PAL gamers can probably notice the artifacts left by programmers not properly refreshing the top and bottom 8 lines.  

Never heard that one before.

NES resolution has always been 256x240.

The Name Table holds "tile index values." Tiles themselves are 8x8

pixels. The entire Name Table itself is 32x30 tiles (256x240 pixels).

 

And we see no artifacting because we have PAL carts to go in our PAL NES's

Shocking I know

[JB]

Myth 4.  The NES has 2KB of CPU RAM available

The NES's console does have only 2KB of RAM for the CPU's use, and an eighth of that is used for the stack, but zero page is totally free for the programmer.  However, the NES can also utilize 8KB of RAM on a cartridge as Save RAM or extra Work RAM or both.  Several Nintendo carts like The Legend of Zelda do the former, Metroid does the latter.  

So THAT'S why Metroid has no save RAM!