NES vs. 5200
Entry posted by vdub_bobby
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NES VERSUS 5200, how does the hardware compare? This question is interesting to me, so I did some research this morning, refreshing my memory and digging a little deeper. I was going to post this in the (latest) thread on the subject in the 5200 forum but it had degenerated into name-calling 
So, anyway, here's what I've got. Please let me know about any inaccuracies or errors!
I'm going to use the term "5200" to stand in for the the 5200 as well as the 400/800 line of computers, so I will be ignoring controller issues.
Colors
5200: 256, 16 luminances of 16 colors (including grays)
NES: A little confusing, 52 is the number most commonly given, but it looks higher than that. There are 12 colors (not including gray) with 4 luminances. There are 4 different "gray" colors, each with 4 luminances. There is some overlap between those grays, but I'm not sure how much - I think there are something like 6 shades of gray. So, my reading of the technical docs is that there are 54 colors (including grays). But! You can also change the "color emphasis," which apparently changes the color of all the colors slightly. I.e., if you select to emphasis green, then all colors will be slightly greener. I'm not sure how much of an effect this has and according to some docs there is overlap between the palettes, but there are 4 settings for the "color emphasis:" normal, green, brown, blue. So the total number of colors is probably at least 100 and as many as 416.
Playfield
5200: Lots of modes to deal with here. We'll start with bitmapped modes, since they don't correspond to anything on the NES, AFAIK. Leaving aside the special GTIA modes, which I don't think I've ever seen used in a game (I'm probably wrong, of course!), there are basically two bitmapped modes: a 320x240 mode and a 160x240 mode. I'm going to use 240 as the vertical resolution for both the 5200 and the NES since they both are capable of outputting that many visible lines, even if neither machine really uses that many. Anyway. The 320 mode is 1.5 color (foreground and background are the same color, with different luminances) and the 160 modes are 5 color including background.
Next, of more interest for direct comparisons: Tile (or character) graphics. The 5200 has several modes, but I will just explain the main four. The first is a screen of 40x30 tiles that are 8x8 each. You can define up to 128 different tiles and display them normal or inversed (as a "negative") (or upside down, for that matter, though upside-down and rightside-up tiles cannot be displayed simultaneously). This is based on the 320 mode and shares the color scheme of that mode: 1.5 colors.
The others are all 5-color modes: First, the two 2-color tile modes. Each tile can be 2 colors, foreground and background, where there are four different foreground colors to choose from. You can define up to 64 tiles, but each one can be displayed in any of 4 foreground colors. I.e., you can display AAAA. There are two variations of this mode, one with twenty 8x8 tiles across each line (pixels are double width) and one with, again, 20 8x8 tiles across each line but with the pixels double-height as well (so only 15 rows of tiles rather than 30).
Finally, there is a 5-color tile mode (including background). These tiles are 4x8 and each pixel can be any of 4 different foreground colors. These 4 foreground colors are the same for all tiles on the screen. There are 40 tiles across the screen and 30 rows. You can define up to 128 of these tiles; I'm not sure whether they can be displayed inversed or upside-down.
NES: Much, much, much more simple. No bitmap mode that I'm aware of. A single tile-mode: A screen of 32x30 tiles, each 8x8. You can define up to 256 tiles. Each is 4-color, including background. The 4 colors are not independently set, though - you can choose from four foreground palettes, so you have 13 colors, including background, to choose from but which of the 12 you choose depends on where on the screen the tile is. Each palette corresponds to certain areas of the screen in, apparently, an odd checker-board pattern (each 32x32 pixel area of the screen is quartered, with each quarter using one of the four palettes).
A note about tiles: though the NES supports many more tiles (256 vs. 128 or 64), you can't easily swap out one set of tiles for another - to do so requires rewriting up to 8K of RAM! On the other hand, you can very easily swap tile sets on the 5200, you just change the base address of your tile set. So you can have as many tile sets as you have memory (RAM or ROM) for and then switch between them as often as several times per frame. It is very easy to animate your tiles this way - you don't even have to rewrite any screen memory, just tell ANTIC to look somewhere different for the tile set. 
Scrolling
5200: Supports fine-scrolling of all graphics modes in all directions.
NES: Supports fine-scrolling in all directions - note that a stock NES only has enough RAM to scroll horizontally or vertically, but not both at the same time. This is only a RAM limitation and could probably be worked around with some fancy trickery. Or more RAM, of course. 
Sprites
5200: Eight sprites, half of which are 8x240 and half of which are 2x240. Each sprite is 2-color (foreground and background) and each smaller sprite shares its color with a matching larger sprite. Or you can combine the 4 smaller sprites into a single larger sprite and then it gets its own color, sort of - it then borrows a color from the playfield. I suppose at this point we have to finally mention interrupts. Using display list interrupts (DLIs) you can do a lot of things, but for sprites you can do two main things: you can change their foreground color line-by-line and you can change their horizontal position in the middle of the screen - you can, essentially, "re-use" a sprite, increasing the number of sprites you can show onscreen. So the 5/8 sprite limit is a hard limit for each scanline but not for the entire display. Finally, with a special setting you can get an additional color: You can overlap sprites and the overlapped pixels will have a blended color, combining the color of both sprites.
NES: 64 sprites (8 per scanline), each 8x8 or 8x16 and each is 4-color (including background). Each sprite can use one of four palettes and can use 3 foreground colors from each palette. I believe you can use DLIs with the NES as well but it is much trickier and not as flexible as the 5200.
So, to sum up some of the color stuff: The 5200 can display 9 colors on each scanline (4 sprites, 4 playfield, and background) or a few more with overlapping/blending and the NES can display 25 (12 sprite colors, 12 tile colors, and background).
Audio
5200: POKEY has 4 audio channels. Each plays a square wave with varying amounts of noise, including a setting which is basically pure noise. The frequency has 8 bits of resolution, the volume has 4 bits of resolution. Can also combine 2 channels into a single channel with 16 bits of frequency resolution. Each channel can also be set to a special mode to play digitized samples, though you have to feed it the raw sample data at the desired frequency. It accepts 4-bit samples.
NES: Here we have more flexibility, and more complexity. Five channels. Two play a square wave, one plays a triangle wave, one plays noise, and one is dedicated to playing digitized samples. The square wave and triangle wave channels each have 8 EDIT: 11 bits of frequency resolution and four bits of volume resolution. The noise channel's frequency has 4 bits of resolution and its volume also has 4 bits of resolution. Also - the noise channel and square channels also have a volume envelope with looping, and the two square channels also have a "sweep" register, which I think increases/decreases the frequency a specified amount at set intervals. Very cool! The channel reserved for playing samples has two modes - in one mode you feed it the raw sample data (7-bit) at whatever frequency you want, in the other it will automatically stream the sample, though the digitized data has to be in a special form. I'm not sure how good the auto-streaming samples sound, but it is a cool feature.
And that's it! The NES clearly has better capabilities - though the lack of a bitmap mode kinda hurts - but, actually, I'm surprised how well the 5200 stacks up against it. I think the main thing that hurts is the resolution difference and having fewer colors to work with. Fewer sprites is another biggie, but not as big as I anticipated - 5 vs. 8 per scanline - though it is easier to handle the 64 independent sprites on the NES versus all the DLIs on the 5200, you can in theory have many more than 64 sprites on a 5200. Also, I think the NES will automatically flicker them for you if you put too many on one line. EDIT: The NES will not automatically update them for you, you have to do that manually.
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